Historical Development of Magnetic Recording and Tape Recorder
Masanori Kimizuka■ Abstract
The history of sound recording started with the "Phonograph," the machine invented by Thomas Edisonin the USA in 1877. Following that invention, Oberlin Smith, an American engineer, announced his idea formagnetic recording in 1888. Ten years later, Valdemar Poulsen, a Danish telephone engineer, invented theworld's first magnetic recorder, called the "Telegraphone," in 1898. The Telegraphone used thin metal wireas the recording material. Though wire recorders like the Telegraphone did not become popular, researchon magnetic recording continued all over the world, and a new type of recorder that used tape coatedwith magnetic powder instead of metal wire as the recording material was invented in the 1920's. The realarchetype of the modern tape recorder, the "Magnetophone," which was developed in Germany in the
mid-1930's, was based on this recorder.After World War II, the USA conducted extensive research on thetechnology of the requisitioned Magnetophone and subsequently developed a modern professional taperecorder. Since the functionality of this tape recorder was superior to that of the conventional disc recorder,
several broadcast stations immediately introduced new machines to their radio broadcasting operations.
The tape recorder was soon introduced to the consumer market also, which led to a very rapid increasein the number of machines produced. In Japan, Tokyo Tsushin Kogyo, which eventually changed its nameto Sony, started investigating magnetic recording technology after the end of the war and soon developed
their original magnetic tape and recorder. In 1950 they released the first Japanese tape recorder.
In the 1960's several cartridge-type tape recorders were developed to meet the requirements of car-stereo
devices, and finally, the compact cassette system was introduced. Japanese manufacturers contributed to
improving the basic recording performance of compact cassette recorders and to expanding the variety ofavailable products, especially small-sized tape recorders. As a result, they attained a large market sharein the worldwide tape recorder market. In 1979 the "Walkman," a portable compact cassette player, wasintroduced to the market, and in a very short period it became very popular all over the world. The productconcept of the Walkman was well accepted, and it changed the style of audio listening dramatically.
In this report I briefly describe the history of sound recording, particularly the progress and relation ofmagnetic recording technologies in the compact cassette system. I also describe the product concept anddownsizing technologies of the Walkman. In the last section, I explain the development of digital audio tape(DAT), an advanced tape recording system that led to the rise of digital audio technology.
Japanese audio manufacturers joined the tape recorder market relatively soon after the end of World War
II. Around 1970 the technical capabilities of device manufacturers increased rapidly, and many superior
devices such as precision mechanical components and high-performance electrical devices became
available on the domestic market. The synergy effect between product design and device technologies
improved the competitiveness of the final products, and Japanese audio manufacturers achieved successin the compact cassette tape recorder market. They changed the style of listening and the audio productitself with their introduction of the stereo-headphone "Walkman" in 1979. They ultimately succeeded ingetting a huge market share of the worldwide audio market.
Many people have recently been enjoying listening to music supplied in a digitally compressed format withsmall portable devices and headphones. However, it is hoped that the Japanese audio industry will develop
a revolutionary new product or service for a more comfortable listening experience with even better sound.

3

■ Profile

Masanori Kimizuka
Chief Survey Officer, Center of the History of Japanese Industrial Technology,
National Museum of Nature and Science, Tokyo
March 1973: 	Graduated from the Department of Mechanical Engineering, Osaka University
April 1973: 	Started working at Sony Corporation
Involved in the design and development of audio equipment and storage equipment
February 2006: Representative Director of Start Lab, Inc.
December 2011:
Left Start Lab
Left Sony Corporation
Present:
Part-time lecturer at Tokyo University of the Arts
Director of Japan Audio Society■ Contents
1. Introduction………………………………………………………………………………………………………………… 185
2. Recording Sound… ……………………………………………………………………………………………………… 187
3. Invention of Magnetic Recording……………………………………………………………………………………… 189
4. Post-war Tape Recorders… …………………………………………………………………………………………… 197
5. Development of Domestically-Produced Tape Recorders… …………………………………………………… 206
6. Emergence of Cartridge-Type Tape Recorders… ………………………………………………………………… 215
7. Structure and Performance of Compact Cassette-Type Tape Recorders… ………………………………… 224
8. Magnetic Tape in Compact Cassettes… …………………………………………………………………………… 227
9. Advances in Magnetic Heads for Compact Cassettes…………………………………………………………… 229
10. Development of Three-Head Compact Cassettes……………………………………………………………………… 234
11. Noise Reduction Systems… ………………………………………………………………………………………… 238
12. Advances in Driving Motors… ……………………………………………………………………………………… 244
13. Towards the "Headphone Stereo"…………………………………………………………………………………… 251
14. Invention of Digital Audio Tape Recorders (DAT)…………………………………………………………………… 258
15. Conclusion… …………………………………………………………………………………………………………… 269
Tape Recorder System Diagrams… …………………………………………………………………………………… 271
Chronological Table… ……………………………………………………………………………………………………… 272
List of Tape Recorders……………………………………………………………………………………………………… 273

1 Introduction
Many thousands of years ago, people painted various images
on rock surfaces. The vivid animal depictions in the famous
Cave of Altamira, thought to have been painted as a ritualto the gods, are still-image records left by the people of thetime. Since ancient times, people have dreamt of recording
sound in the same way as pictures; however, they lacked
the means to record it, other than passing it down throughthe oral traditions of story and song. When writing wasinvented, people could record their voices through thisinnovative means of “recording words using letters”. With
regard to music, however, capturing the sound itself held
more significance than the recording of mere words. People
devised notation systems as a means to record the sounds ofmusic and a number of civilisations had their own notations
and symbols for this purpose. However, this “sheet music”
was still an indirect means of recording music. The recordingof sound itself remained a dream.
Around the mid-19th century, Frenchman Édouard-Léon
Scott de Martinville devised a machine that could record thechanges in a sound waveform against a time axis, based on
the idea that sound is transmitted as a wave. Although Scottde Martinville’s machine could record sound waveforms, it
could not reproduce the recorded waveform as sound. In 1877,
around 20 years later, American inventor Thomas Edison
invented the “phonograph”, a machine that could reproduce
sound by producing a vibration from a sound waveformrecorded on a brass cylinder wrapped in tin foil. For the firsttime in human history, a machine could record and reproduce
sound. The more advanced gramophone record was a later
improvement to the device. This advancement meant that thedevice could be developed not only as a sound recorder, butalso as a household music player through these records. As
radio broadcasting gained popularity, disc recorders became
vital pieces of equipment for recording and playing backsound, used by many broadcasting offices until the end of
the Second World War. While records improved in quality,
increased in length and progressed to stereo, the principle ofsound recording remained the same: mechanically recordingor etching raw sound waveforms onto media.
Telecommunications technology developed rapidly in the
19th century and telegraphy became increasingly morepractical. In 1876, American inventor Graham Bell invented
the telephone, which could transmit sound itself. Based on
the idea that telephonic sound is converted into electricity
and could thus be recorded in the form of magnetic changes,
American Oberlin Smith published the world’s first article on
the concept of magnetic recording. In 1898, inspired by thisconcept, Danish engineer Valdemar Poulsen used steel wireto build the “Telegraphone” wire recorder, the world’s firstpractical magnetic recording machine.
Just before the Second World War, a magnetic recording
machine was proposed in Germany, which replaced the steel
wire with tape, making it easier to use. This was the birthof the prototype tape recorder. While the war prevented
countries from exchanging magnetic tape recording
technology, research progressed in Germany and thetechnology continued to improve. By the end of the war,
the tape recorder was complete, equipped with advanced
technology such as AC bias and stereo recording. Afterthe war, the Allies carried out a detailed investigation of
all German technology related to magnetic recording; thistechnology then became widely used in the development oftape recorders in the United States. Ampex, a small, newlyfounded company, took on the challenge of developing thetape recorder in the United States; before long, it was anindustry-leading corporation, making major contributions
to the technical advancement and development of the taperecorder. With Europe lagging a little behind the times,
Studer, a small Swiss company, began to develop the taperecorder there. It developed superior models, from businessmachines to luxury consumer products, and became theleader of the industry in Europe. In Japan, Tokyo Tsushin
Kogyo (later Sony), founded not long after the end of thewar, persevered in researching magnetic recording, believing
in its potential. In 1950, the company completed the first
domestically-produced tape recorder in impoverished postwar Japan. After the war, tape recorder technology and its
potential star qualities went public. Venture companies inJapan, Europe and the United States alike took on the taperecorder challenge, and a number of interesting designs
emerged.
While tape recorders first gained popularity for business
use, companies soon began to develop models for generaluse as well, and these machines quickly gained popularity
for household use. In the United States, they became thepopular choice of audio equipment for entertainment withthe sale of music tapes, which had converted to stereo much
faster than records had. Companies began to focus on easyto-use cartridge-style tape recorders, with car stereos as apossible application. In the early 1960s, companies began
to propose multiple-cartridge systems. A compact cassette
proposed by the Dutch company Philips established itself
as the effective global standard with a royalty free patent
licence policy. By this time, Japanese companies were
becoming more confident in their development and design of
AV equipment. Parts manufacturers, who supplied electronic
components and equipment parts, began to improve theirtechnological capabilities, developing better quality and more

Historical Development of Magnetic Recording and Tape Recorder185

advanced parts and actively working to incorporate theminto their designs. Like the compact cassette tape recorder,
technological developments were standardised, high inperformance and packed with features. This work required
perseverance and meticulous attention to detail, but Japanesecompanies were well suited to this and ended up leading
the compact cassette tape recorder industry. At the sametime, other audio equipment also began to be sought after
around the world. The 1970s and 1980s ushered in a golden
age for the Japanese audio industry. Given the popularity ofcompact cassettes, the headphone-equipped portable stereo,
the Walkman, appeared in 1979. This embodied a completely
new audio concept. Music, which had previously been
limited to within the home, could now be taken outdoors andenjoyed alone anytime, anywhere. This hit product swept the186

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world, causing a revolution that fundamentally altered theway we listened to music.
This report begins with the history of sound recording, andthen touches on the invention of magnetic recording andthe development of the early open reel tape recorders in
Chapters 2 to 5, before going on to discuss the developmentof component technologies of the compact cassette tape,such as tape, heads, noise reduction and motors in Chapters
6 to 12. Chapter 13 describes the development of compact
cassette equipment and the creation and development of the
Walkman, the headphone-equipped portable stereo. Chapter
14 describes the development of digital audio tape recorders(DAT), typified by the compact disc, at the leading edge oftechnology in the digital audio age.

2 Recording Sound
2.1

Sound Recording by Scott deMartinville

Writing was invented as human civilisations developed,
making it possible to record and pass on various matters. As
writing developed, it enabled large amounts of knowledge
to be kept on a broad range of areas for a long period oftime, facilitating the further advancement and expansion ofcivilisation. From the dawn of time, writing (and pictures)by humans was the sole means of keeping records. It was
the dream of humankind since ancient times to store andreproduce voice and music, or the sounds themselves, but
this dream was not readily achieved. Much trial and error
took place in the 19th century to achieve this dream based on
rapidly advancing modern science and technology, and somemajor results had been achieved even before the advent of
the 20th century.
Sound is a wave that travels through the air; it is acompression wave that alters with time. Accordingly, inorder to record sound, it is necessary to record the changes
in that wave against a time axis. Based on the idea thatsound could be recorded if air density could be captured
as an oscillation, French printer Édouard-Léon Scott deMartinville succeeded in recording a waveform in 1857. His
device captured sound through a plaster horn and transmitted
it to a diaphragm; a pig bristle attached to the diaphragmrecorded the sound waveform in lampblack onto a cylinder.
The cylinder was turned on its axis with the sound waveformrecorded in a continuous line on the surface of the cylinder.
This instrument was named the phonautograph; many ofthese were manufactured as experimental equipment forsound recording (Fig. 2.1). A further improvement was madeto the device by wrapping it with paper coated in lampblack,which could then be kept as a recording paper, rather thancoating the cylinder itself. While the phonautograph could
record sound, it could not play it back, as it had no means to
reproduce the original sound from the waveform. However,it excited many scientists and engineers, who became
engrossed in trying to invent a machine that could record andplay back sound.

Fig. 2.1. 	Édouard-Léon Scott de Martinville’s“Phonautograph” (1)2.2

Invention of the Phonograph

In 1877, 20 years after the phonautograph was invented,
American inventor Thomas Edison succeeded in making
a device that could record and play back sound using acylinder like the phonautograph. The cylinder was madeof brass, wrapped in tin foil and fitted with a handle on its
axis. Cylindrical tubes fitted with diaphragms with needles
attached were arranged on either side of the cylinder. Thesetubes worked respectively as a microphone for recording
and a speaker for playback. To record sound, one pressed
the microphone needle against the cylinder and wound
the handle. When one spoke into the microphone tube,
the needle would record the sound on the tin foil on thecylinder. To play the sound back, the needle on the playback
diaphragm would trace the groove created during recording;the diaphragm would vibrate according to the recorded
waveform and convert it back to sound. This was a veryclear and simple mechanism. Edison immediately decided toapply for a patent, naming this instrument the “Phonograph”(Figs. 2.2, 2.3). While it seems to have been based on theidea of Scott de Martinville’s phonautograph, it was full oforiginal ideas and experimentation, such as using tin foil
as a recording media and the unique construction of thediaphragm and needles. The phonograph finally achieved
the dream of recording sound for the first time in history.
The invention of the “talking machine” immediately became
known throughout the world, as did the name “Phonograph”.
It appeared in an article in a Japanese literary magazine thefollowing year in 1878 with a translated name meaning “voice
reproduction device”. In 1879, Englishman James Ewing,a lecturer at the University of Tokyo, carried out a public
experiment for himself. The president of the Tokyo Nichi
Nichi Shinbun newspaper, Genichiro Fukuchi, who attended
the experiment, coined the Japanese term chikuonki meaning“sound storing device” that later took hold in Japan as thename for the gramophone.

Historical Development of Magnetic Recording and Tape Recorder187

Fig. 2.2. Patent document for the Phonograph (2)for the business model of reproducing recorded discs andselling them in large quantities as records. Creating a mouldby carefully reproducing a groove etched into a master discthen using that mould to produce large quantities of copies
was the prototype for modern record production. This wasvitally instrumental to the development of the recording
and music industries. The discs were far more suited to thereproduction process than were the cylinders; this became
the trump card to conclude the market battle between thetwo formats. These records were the mainstay of recorded
music until the late 20th century. Technical improvements
to disc records continued to develop, such as long-playing
capabilities, improved sound quality and stereo sound,although the principle of producing sound by mechanicallytracing a groove etched onto a disc remained fundamentallythe same as it had been in Berliner’s gramophone.

Fig. 2.3. Edison’s “Phonograph” (3)Fig. 2.4. Berliner’s “Gramophone” (4)References

2.3

Appearance of Disc Gramophones

There was much interest in the gramophone at the laboratory(later Bell Laboratories) founded by Graham Bell, theinventor of the telephone. Researchers at the laboratory
hoped to study improvements to the gramophone; one ofthese was Emil Berliner. Berliner moved to the United Statesfrom Germany at the age of 19 and worked as a technician
on research to improve the gramophone. He was greatly
impressed and excited by Edison’s cylinder phonograph andhad a good understanding of its inherent issues. Edison’s
device recorded sound by etching a waveform onto acylinder in a vertical direction, with the depth of the groovechanging with the volume of the sound. Feeling that thiswould distort the sound, Berliner came up with a system of
etching the waveform in a horizontal direction. Berliner alsocame up with the idea of using flat, disc-shaped recording
media instead of cylinders. Thus, the disc gramophoneand gramophone records were conceived in 1887, 10 years
after Edison’s phonograph. This instrument was named the“Gramophone” (Fig. 2.4), marking a very significant pointin the history of sound recording. Berliner did not stop at
simply inventing the gramophone, he also devised the basis

188

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012(1)	Mori, Yoshihisa, et. al. Onkyō-Gijutsu-Shi [History ofSound Recording], Tokyo University of the Arts Press,
March 2011, p. 16.
(2) Ibid., p. 20.
(3) Ibid., p. 18.
(4) Ibid., p. 27.

3 Invention of Magnetic Recording
3.1

The Work of Oberlin Smith

Edison had turned humanity’s dream of recording soundinto reality. Berliner had improved on the cylinder
phonograph, creating the disc gramophone. The inventionof the gramophone had implications that went beyond
merely recording sound; it created an industry from a newstyle of entertainment in the form of listening to music athome on duplicated records. The underlying principle of thegramophone was that of mechanically recording a soundwaveform onto a medium and reproducing that waveform
as an oscillation. Around 1888, American mechanicalengineer Oberlin Smith devised and published an idea for adevice for recording voices transmitted by telephone basedon a completely different principle from that used in thegramophone. Inspired by the phonograph, Smith was the firstin the world to come up with the idea of magnetic recording,which differed completely from mechanical recording
methods. Believing that more information could be gatheredby making this available to the general public, he published
his idea in The Electrical World without patenting it. The
concept of magnetic recording published by Oberlin Smith isgiven below.
“The following proposed apparatus is, however, purely
electrical, and is, as far as known to the writer, the only one
fulfilling such conditions that has been suggested. [Fig. 3.1(a)] is the recording part of an electrical phonograph. [Fig. 3.1(b)] is the talking part of the same. Many of the pieces, as D,
E, B, C, etc., can be the same ones as are used in [Fig. 3.1 (a)].
… In [Fig. 3.1 (a)] the voice or other sound is delivered into
an ordinary telephone A. Preferably, this should be a carbon
transmitter so as to have s battery F in the circuit, and thus
use as strong a current as practicable. Possibly, however, aBell telephone without a battery would answer the purpose.

In either case the current, broken into waves of varying
lengths and intensities corresponding with the vibrations of
the diaphragm in the telephone, passes in its circuit throughthe helix B, converting into a permanent magnet any pieceof hardened steel which may be at the time within the helix.
Through this helix B passes a cord, string, thread, ribbon,
chain or wire C, made wholly or partly of hardened steel,and kept in motion by being wound on to the reel E from off
the reel D, E being revolved by hand, clock-work or othermeans. J is a tension spring or brake pressing against D to
keep the cord C taut.
When in operation with the undulatory current from thetelephone A passing through the helix, the cord C becomes,
so to speak, a series of short magnets grouped into alternateswellings and attenuations of magnetism.
The actual lengths of these groups depends upon the speedof their motion, but their relative lengths depend upon
the relative lengths of the sound wave; and their relative
intensities depend upon the relative amplitudes of thesewaves. The cord C therefore contains a perfect record of thesound, far more delicate than the indentations in the tin-foilof the mechanical phonograph. The probable constructionof C would be a cotton, silk or other thread, among whose
fibres would be spun (or otherwise mixed) hard steel dust,or short clippings of very fine steel wire, hardened. Eachpiece would, of course, become a complete magnet. Other
forms of C might be a brass, lead or other wire or ribbon
through which the steel dust was mixed in melting—being
hardened afterwards in the case of brass or any metal with ahigh melting point. … Another imaginable form of C would
be simply a hard steel wire, but it is scarcely possible that
it would divide itself up properly into a number of shortmagnets. … If it could be made to work it would obviously
be the simplest thing yet suggested.”

(a)

(b)
Fig. 3.1. Oberlin Smith’s Wire Recorder Idea

Excerpt from Smith’s article in The Electrical World, 8 September 1888.
(50 Years of Audio, 1986. Japan Audio Society Publishing, reprint. English text excerpt taken fromhttp://oberlinsmith.org/Library/Library-PDFs/The Electrical World 8 Sep 1888.pdf, accessed 19 December 2012.)

Historical Development of Magnetic Recording and Tape Recorder

189

3.2

Invention of the Wire Recorder

The publication of Oberlin Smith’s idea was truly groundbreaking in terms of technological developments in magnetic
recording. Many engineers were inspired by this article andset about trying to develop magnetic recording devices.
In 1898, 10 years after Smith published his idea, Danish
telephone engineer Valdemar Poulsen invented the world’s
first magnetic recorder, using steel wire as a recording
medium. This device, shown in Fig. 3.2, is very similar in
structure to Edison’s phonograph, except that the cylinder iswrapped in steel wire rather than tin foil or wax and it has aelectromagnet touching the wire. This magnet plays the samerole as the needle used in the phonograph. As the cylinder
revolves, the magnet runs along the wire, using continuous
magnetisation to record sound on it. To play back the sound,the magnetised wire is run through the same electromagnet,
allowing the recording to be reproduced as an electricalcurrent induced in the coil through magnetisation. Poulsen
called this instrument the “Telegraphone”. As a telephone
engineer, he apparently intended to record voices transmitted
by telephone (an answerphone, so to speak). Poulsen gained
patent rights for the telegraphone in Denmark, the UnitedStates, the United Kingdom, France and other key countries
and embarked on a major marketing campaign for it.
Although the telegraphone had promising prospects with awell-received exhibit at the Exposition Universelle in 1900
in Paris, it failed as a business venture, as the products werefraught with problems: the quality was not good enough, they
were prone to breaking down, and it was difficult to achieve
the desired sound quality. The improved development andperformance of the disc recorders and the popularity of therecord industry boosted the dominance of the gramophone
and the magnetic wire recorder was largely forgotten by the
public. Poulsen and his assistants worked hard to improve
the performance of magnetic recording and achieved
some results that would later become relevant, such as theinvention of DC bias.

Fig. 3.2. Poulsen’s “Telegraphone” (1)3.3

Invention of DC Bias

While the telegraphone business venture failed to takeoff, Poulsen and his assistant Peder O. Pedersen worked
hard to improve the telegraphone. In 1907, they acquired

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Fig. 3.3. Poulsen’s Telegraphone patent (2)patent rights in the United States for their DC bias system.
The DC bias technology was very effective in improving
sound quality by increasing the sensitivity of the recording
and reducing distortion. It became an essential piece oftechnology for magnetic recording in devices such as
the wire recorder for the next 30 years until AC bias wasinvented.
When a magnetic field is externally applied to a magnetic
substance and gradually strengthened, the internal magnetic
flux of the magnetic substance also increases; however, it
only increases to a certain extent. The magnetic flux at thispoint is called the maximum magnetic flux density (Bm).
If the external magnetic field is reduced to 0 at this point,
the magnetic substance retains its internal magnetic flux
density rather than also returning to 0. This means that themagnetic substance has become a magnet (it has become
magnetised). This magnetic flux density is called residual
magnetic flux density (Br); the substance will never becomea stronger permanent magnet than it is at this point. The
north pole of a magnet created through magnetisation in one
direction would have become the south pole of the magnet
if the magnetisation were to have taken place in the opposite
direction. The magnetic field forms a symmetrical curve
corresponding to the strength of the magnet, as shown in Fig.
3.4. This curve is called the magnetisation curve or hysteresis
curve.
When a completely non-magnetised material is magnetised,
the magnetization follows the 0-a, 0-c curve shown in
Fig. 3.4. In the initial stage, this curve is called the initial
magnetisation curve. In a magnetic recorder, the horizontal
axis corresponds to the recording magnetic field applied
to the magnetic material (wire, later magnetic tape) by

the head, while the vertical axis shows the intensity of themagnetisation. The magnetic field produced by the head isin proportion to the strength of the recording signal, thatis, the recording current flowing through the head. Since
the initial magnetisation curve is not a straight line, theresult of magnetisation will be a distorted waveform even
if a magnetic field is applied according to the sound being
recorded. This is called unbiased recording, shown in Fig.
3.5. Significant distortion occurs where a recording is madewhere the magnetisation curve is not in a straight line.
Having the recording current as DC and using a near-straightmagnetisation curve reduces distortion and produces bettersound quality. This is called DC bias recording. While using
straight-line section a of the magnetisation curve shown in
Fig. 3.6 reduces distortion, as shown in Fig. 3.7, if we lookat the overall magnetisation curve, we see that section b on
the outer loop is a longer straight-line section, so it would bebetter to use section b. First, a magnetic substance is applied
to a saturation field to create Br; the substance is then biased
in one direction without reducing the magnetic flux density;
the recording current is then added and DC bias recording
can be achieved using section b, as shown in Fig. 3.8. This
was the DC bias method invented by Poulsen and Pedersen,
achieving good recording quality by using long straightsections of the magnetic curve.

Fig. 3.6. Straight line section of magnetisation curve (5)Recording waveform

Playback waveform

Fig. 3.7. DC bias recording (6)Recording waveform

Playback waveform

Fig. 3.8. DC bias recording 2 (7)Fig. 3.4. Magnetisation curve (3)Recorded waveform

Input waveform

3.4

Advances in the Wire Recorder

Poulsen continued working hard to promote the wire recorder,
setting up a sales company in the United States in the hopeof popularising it. He also continued to make improvements
to the telegraphone itself, but he was never able to dominate
the market because the device was lacking both in terms ofcompetitive pricing and in the degree of technical perfection
required for ease of use and good performance. The wire
recorder failed as the popular choice of sound recorder due
to the growth and development of the disc gramophone.
However, by the late 1920s there was a growing interest in
magnetic recorders in fields such as broadcasting and militaryFig. 3.5. Distortion due to unbiased recording (4)Historical Development of Magnetic Recording and Tape Recorder191

communications and further research began to be carriedout, especially in the West. One feature of the wire recorder
was that it could play continuously for longer periods thanrecords; there was a demand in these fields for such a feature.
These recorders were actually implemented in some areasin Europe, such as the large, steel ribbon recorders usedin broadcasting, which replaced the steel wire with steel
foil as the recording medium. Fig. 3.9 shows an improved
telegraphone from around 1920. This is an archetypal taperecorder, with the wire-wound reel driven by a motor and useof the left and right reels alternating when the recorded wireis rewound. Fig. 3.10 shows a British Marconi-Stille steel
ribbon recorder used for broadcasting by the BBC. This hugedevice weighed one tonne and could record for 30 minutes
on a steel ribbon that was 3mm wide, 80μm thick and 3,000m
long. One of these was imported by Japan in 1937 and used
for foreign-language broadcasting by NHK Tokyo.

of whether a more suitable material could be used as arecording medium for a magnetic recorder that was easier
to use and could overcome these drawbacks. Although theidea to coat a tape of soft material with a powdered magnetic
substance was proposed by A. Nasavischwily in Germany
and Joseph A. O’Neill in the United States in the 1920s,
nobody had managed to build a working machine. In 1928,
German engineer Fritz Pfleumer coated paper tape with ironoxide to create a “recording tape” and made the world’s firsttape recorder, called the “Sound Paper Machine”. While thismachine had all the basic elements of a tape recorder andcould be hailed as the world’s first tape recorder, it cruciallylacked in performance and could not produce a satisfactory
quality of sound. The coated magnetic tape did not have aneven surface and the coating was not very well attached;during playback the magnetic particles would scatter on
coming into contact with the head. Due to this, it became
known as the “Sandpaper Machine”.

Fig. 3.9. Telegraphone, circa 1920 (8)Fig. 3.11. Fritz Pfleumer’s “Sound Paper Machine” (10)Fig. 3.10. Marconi-Stille steel ribbon recorder (1937) (9)3.5Invention of the Tape Recorder

3.5.1 Sound Paper Machine
The wire recorders and steel ribbon recorders were certainly
not easy to use. They used solid metal recording media; if
the wire came unwound it was extremely difficult to put
it back; if it broke, it had to be welded back together. It is
not difficult to imagine that the question was often posed

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3.5.2 Creation of the Magnetophon
Pfleumer was granted patent rights in 1930 and took theworld’s first tape recorder to all of the major electricalmanufacturers in Germany to try to market it, but could
not raise much interest because despite the potential of thetechnology, it lacked in performance.However, in 1932,
the president of Allgemeine Elektricitäts-Gesellschaft(AEG) showed some interest, buying the patent rights from
Pfleumer. AEG immediately set up a research laboratory
on magnetic recording and set about improving the Sound
Paper Machine and the magnetic tape. Being an electricalmanufacturer, AEG needed experts in chemistry to improvethe magnetic tape and sought assistance from IG Farben.
Consequently, the IG Farben’s Ludwigshafen factory (laterBASF) ended up collaborating on the magnetic tape project.
While IG Farben worked on developing the tape, AEG put
its efforts into research and development of the magnetic
recorder, completing the forerunner to the modern taperecorder – the “Magnetophon” – in 1934 (Fig. 3.12). AEG

planned to exhibit it at a radio show that year, but several
defects were discovered in the drive train and the amplifierright before the show, so the exhibit was withdrawn. AEG
made further improvements to the drive mechanism and otherparts and enclosed the mechanism unit, the amplifier unit andthe speaker unit in separate housings. The combined systemwent on display at the Berlin Radio Show in 1935 as the “K1
Magnetophon”. The world’s first practical tape recorder andmagnetic tape was successfully demonstrated in public. As
well as having high-quality tape developed by a specialised
manufacturer, it had a stable tape drive system and ring heads

superior for recording sound. The Second World War ended
in 1945 with an Allied victory. Magnetophon technology was
analysed by the Allies, leading to the development of highly
efficient tape recorders in the United States.

Fig. 3.13. Magnetophon (1943) (12)Fig. 3.12. An early Magnetophon (ca. 1934) (11)that would not put excess pressure on the tape and damage it.
These developments meant that the Magnetophon had mostof the elements of a modern tape recorder.

3.5.3 Popularity of the Magnetophon
AEG developed a range of other models after the K1
Magnetophon, such as a console model and a portable model.
These began to be used for monitoring radio broadcasts
and recording military and police interrogations. While
broadcasting offices mainly used disc recorders, most of
the broadcasting offices in Germany had Magnetophonsinstalled by the outbreak of the Second World War in 1939.
The adoption of AC bias in 1942 made a major improvement
to the sound quality, which had previously not been as goodas the disc recorders. High-quality, pre-recorded broadcasts
began to be transmitted all across Europe. The Allied Forces,
thinking that such a high quality broadcast could only be
live, were mystified at how these shows could be broadcast
continuously (Fig. 3.13).
Although the Magnetophon gained popularity in Germany
as a new, high-quality recorder, all international technology
exchange stopped at this time, as the machine with its
broadcasting and recording uses would be particularly helpful
to the military. The main sound recorders in the West at thetime were the disc recorders; while there were some steel
wire/ribbon recorders in use, they were not really practical
recording machines. Magnetophon technology was clearly

3.6

Discovery of AC Bias

3.6.1 American Research
Around 1920, the United States Naval Research Laboratory
was researching how to reduce telegraph transmission times
using magnetic recording. The idea was that recordings
made at normal speed could be transmitted at high speed andrecorded at high speed at the receiving end, thereby reducing
the transmission time. Although this was never implemented
due to the difficulty of high speed recording, AC bias was
discovered by chance during the course of this research. In
1921, laboratory researchers Wendell Carlson and Glenn
Carpenter discovered the AC bias effect while experimenting
with magnetic recording when their amplifier oscillated
unexpectedly, acting as a high-frequency bias. This invention
was patented in the United States in 1927. Although thisshould have radically improved the performance of magnetic
recording, it was overlooked as a means of improving
recording, being primarily used for noise reduction.
In the mid-1930s, Bell Laboratories carried out someresearch on AC bias with a view to improving theperformance of steel wire/ribbon recorders. In 1937, Bell
Labs developed the endless-loop style “Mirrophone”. A
stereo-capable model using AC bias was demonstrated at the1939 New York World’s Fair. Dean E. Wooldridge of Bell
Labs put in a patent application for the results of the AC bias
research in 1939 and a US patent was registered in 1941.
The patent was later given over to Marvin Camras fromthe Armour Institute/Illinois Institute of Technology and an

Historical Development of Magnetic Recording and Tape Recorder193

improved version, later known as the Camras Patent, madea big impact in the world of magnetic recording. While ACbias was rapidly adopted by Armour Institute in 1941 foruse in wire recorders for the navy and other applications, thesound recorders themselves still had the usual performance/
function limitations of wire recorders.

3.6.2 Research in Germany
While Germany had built the first modern tape recorder inthe form of the Magnetophon, by around 1930, all magnetic
recorders, including steel wire/ribbon recorders, were using
the DC bias method invented by Poulsen.
In 1938, the German state broadcasting company made thedecision to use the K4(S) Magnetophon for broadcasting. Dr
Hans-Joachim von Braunmühl, chief engineer of the statebroadcaster’s research laboratory, appointed Walter Weberto the task of improving the quality of the Magnetophon. In
1939, while experimenting with circuits, Weber discoveredby chance how high quality recording and playback could
be achieved, radically improving sound quality in termsof frequency response, noise and distortion. Weber knewthat this improvement was caused by abnormal oscillationin the recording circuit and eventually managed to makea recording using AC bias by chance. He spent some time
examining the idea and formalised the AC bias method in
1940. In July that year he applied for a German patent.
The adoption of AC bias saw rapid improvement in theperformance of the Magnetophon, producing far greater
recording and playback quality than could be achieved
through DC bias. AEG prepared to introduce AC bias to
the wider community by staging public demonstrations andother activities. In 1942, AC bias was used in Magnetophonsfor broadcasting. This enabled pre-recorded broadcasts ofextremely high quality for the time to be transmitted all
across Europe up until just before the war ended.
3.6.3 Research in Japan
Japanese research on magnetic recording began in the late
1920s. Dr Kenzo Nagai of the Tohoku University Faculty ofEngineering, who was researching voice delay devices with
the idea that they would be useful in studying submarine
acoustics, began researching magnetic recording aftercoming up with the idea of using a proposed recording on an
endless steel wire as a delay device. This research developed
into a study on the wire recorder and followed on to appliedresearch, such as on proposed secret communications using
magnetic recording. With collaboration from the university’s
Institute for Materials Research, Nagai studied the mostsuitable material to use for wire recording and the Institutefor Materials Research developed a magnetic material called
Sendai Metal (an alloy of 40% steel, 40% nickel and 20%
copper) which was very good for recording. In 1936, Nagai

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also carried out an experimental “pre-recorded broadcast”
with NHK Sendai. Following on from this, he also
successfully made a live recording of whaling in the sea off
Kinkasan with collaboration from Anritsu Electric. Although
he used a trial wire recorder for this experiment, it succeededin recording aboard a rocking boat, which was impossible to
do with a disc recorder. It was quite a long recording and had
to be edited down to around ten minutes for broadcasting.
Although it was quite a difficult task to cut and re-join
the thin wire, it meant that pre-recorded broadcasts were
now possible in an age in which live broadcasting was thenorm. However, there was a lot of background noise in therecording and so pre-recorded broadcasts were deemed
unsuitable for regular use in broadcasting. Accordingly,
Nagai’s laboratory then set about researching noise reduction.
Teiji Igarashi, a researcher from Nagai’s laboratory who hadgone to work with Anritsu, was also researching applications
for magnetic recording at this time. Igarashi discovered
AC erasure by chance in an experiment and confirmedthat this drastically reduced background noise. Although it
did not improve sound quality, it was able to reduce noise
without needing the existing method of DC erasure andwas thus granted a patent. This motivated Igarashi to repeat
the experiment to optimise the process by altering the AC
frequency and intensity, thus perfecting the AC bias method.
Given the fact that Nagai had achieved the same approximate
results earlier than Igarashi and Anritsu had had technicaladvice from Nagai from the beginning, Anritsu Electricaland Nagai jointly applied for an AC bias patent, which was
granted in 1940.

3.6.4 AC Bias
AC bias is a method of recording in which a higher frequency
signal (the bias signal) is recorded along with the recording
signal. This method produces a better quality of magnetic
recording than DC bias and is an indispensable means for
improving the performance of modern tape recorders. This
technology is now used in all analogue tape recorders. The
higher the frequency of the superimposing bias signal,
the greater the expected performance; yet wavelengths ofbetween 30 kHz and 200 kHz are generally chosen, taking
into account the saturation of the head.
As shown in Fig. 3.14, the recording current flowing throughthe head during AC bias recording takes a waveform suchas (c), produced by recording input signal (a) superimposingwith bias signal (b). Recording should be achieved bythis signal being applied to the head and the tape passing
through the gap in front of the head. However, when ahigh frequency bias current is superimposed with the input
signal (here, the sound current), a recording current asshown in Fig. 3.15 (B) flows through the head, generating
an alternating magnetic field. Looking at one point on theTable 3.1. AC Bias Patents (13)Application Month Day Patent Month Day
Year
Year

Country

1902

Jun

12

1907

Dec

10

USA

879,083

Telephone

Valdemar Paulsen
Peder O. Pedersen

111,305

DC bias patent

1921

Mar

26

1927

Aug

30

USA

1,640,861

Radio Telegraphone System Wendel C. Carlson
Ollen W. Carpenter

456,020

AC bias patent

1936

Jun

05

Japan

The Journal of the
A Study of Noise in
Kenzo Nagai, Shiro
Institute of Electrical
Magnetic Recording Systems Sasaki, Junosuke Endo
Communication No. 180

AC erasure

1936

Oct

12

Japan

119,071

Magnetic Recording Devices Teiji Igarashi, Saburo
Not Requiring Peripheral
UtsugiEquipment
Patent held by Anritsu
Electrical Co., Ltd.

AC erasure and AC
bias patent

1938

Feb

05

Japan

The Journal of theInstitute of ElectricalCommunication No. 7

An Experimental Examination Kenzo Nagai, Shiroof the AC Blowout Method in Sasaki, Junosuke Endo
Magnetic Recording

AC erasure

1938

Mar

14

1940

Jun

21

Japan

136,997

A Magnetic Recording System Teiji Igarashi, Makoto
Having AC as a “Bias”
Ishikawa, Keizo Nagai
Patent held by Anritsu
Electrical Co., Ltd.

AC bias patent

1939

Jul

29

1941

Mar

18

USA

2,235,132

Magnetic Telegraphone

Dean E. Wooldridge
287,192(assignor: Bell TelephoneLab.)

AC bias patent

1940

Jul

28

1943

Nov

04

Germany 743,411

Verfahen zur magnetischen
SchaaaufzeichungHans J. von Braunmühl
Walter Weber

AC bias patent

1941

Oct

02

1943

USA

Method of Magnetic Sound
Recording

1941

Dec

22

1944

1937

Feb

Jun

03

13

USA

Patent No.

2,351,004

Marvin Camras(assignor: Armour
Research Foundation)

Accepted

Notes

413,380

Same patentapplied for in USA

423,928

AC bias patent

Bias waveform
Recording head coilcurrent waveform

Sections 3.6.1 to 3.6.3 discuss the progress of research invarious countries. It is interesting to note that in each case an
unexpected oscillation in the amplifier during an experimentcaused a successful result purely by chance. In each case,researchers also came to the conclusion that erasing residual
magnetisation would produce better recording quality.
While AC bias could be considered to be a more intuitively
elusive phenomenon than DC bias, it was made to work bychance and ended up becoming a vital technology that vastly
improved the recording quality of tape recorders.

Method and Means ofMagnetic recording

Inventor

Input signal
waveform

tape that has passed through, the magnetic field changes, as
shown in Fig. 3.16, and the final magnetisation is recorded(the south pole in the case shown in Fig. 3.16). Since thestrength of the magnetisation is proportionate to the input
signal, it is possible to record with very little distortion. Thisis represented on curve B-H in Fig. 3.17, which shows thechanges in the magnetic field affecting the tape. AC bias
recording means that the tape is temporarily magnetised tosaturation, so that recording can take place irrespective of theinitial magnetisation curve. Where the input signal is 0, thetape magnetisation is also 0, meaning it has been AC erased.

Name of Invention / Thesis

Fig. 3.14. AC bias recording waveforms (14)Historical Development of Magnetic Recording and Tape Recorder

195

References(1) 	 Mori, Yoshihisa, et. al. Onkyō-Gijutsu-Shi [History ofSound Recording], Tokyo University of the Arts Press,
March 2011, p. 73.

Sound
High
current frequency(enlarged view)(2) Ibid., p. 73.
(3) Tēpurekōdā no Kiso [Tape Recorder Basics]. Sony

Tape progression

Inc. Technology Education Center, May 1985, p. 34.
(4) Ibid.
(5) Ibid., p. 35.
(6) Ibid., p. 36.

Fig. 3.15. Tape magnetisation process(15)(7) Ibid.
(8) Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono
1 [The Story of the Tape Recorder 1]”, JAS Journal
2004, Vol. 44, No. 7.

Uniform(9) Ibid.
(10) Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono
2 [The Story of the Tape Recorder 2]”, JAS Journal
2004, Vol. 44, No. 8 & 9.

Fig. 3.16. Residual magnetisation at a certain
point on the tape(16)(11) Ibid.
(12) Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono
1 [The Story of the Tape Recorder 1]”, JAS Journal
2004, Vol. 44, No. 7.
(13) Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono
33 [The Story of the Tape Recorder 33]”, JAS Journal
2004, Vol. 48, No. 5 & 6.

Residual magnetic
flux density(14) Tēpurekōdā no Kiso [Tape Recorder Basics]. Sony
Inc. Technology Education Center, May 1985, p. 37.
(15) Ibid.
(16) Ibid.
(17) Ibid., p. 38.

Fig. 3.17. Magnetic field temporarily
reduced through AC bias (17)196

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4 Post-war Tape Recorders
4.1

United States

4.1.1 Creation of Ampex
In July 1945, two months after Germany surrendered,John Mullin of the US Army Signal Corps encountered theMagnetophon at a radio station on the outskirts of Frankfurt.
Mullin, who had been investigating German communication
technology, was captivated by its performance capability. By
the end of the year, he had acquired several machines anddozens of tapes, immediately sending them off to the UnitedStates for a more detailed analysis. With the help of a friend
at home in San Francisco, Mullin set about repairing andimproving the confiscated Magnetophons, replacing the DC
bias system with AC bias (the Magnetophons he acquired
were the old K4 models that used DC bias) and redesigning
the electrical circuits and began to make some test music
recordings (Fig. 4.1). He created a major stir on 16 May 1946
when he demonstrated his new and improved Magnetophon
at a meeting of the IEEE in San Francisco.

a major concern for the “Bing Crosby Show”, a popularradio programme at the time that was on its way to being
broadcast nationwide, to maintain the sound quality of
the recording. Bing Crosby staff members investigating
the use of the Magnetophon for making high quality prerecorded broadcasts were very interested in the Ampex
200 demonstration and offered to help with getting thesystem introduced to radio stations. Being a newly founded
company, Ampex had no marketing channels through which
to target radio stations. It signed an agreement for themarketing to be carried out by Bing Crosby Enterprises andsoon the Magnetophon was being delivered to the ABC to be
put to use in radio broadcasts. With the 200 model accepted
for use by radio stations, Ampex released the improved
300 model in 1949, establishing its firm standing in thefield of tape recorders for business use. Compared with theexisting disc recorders, the machine was ground-breaking
in terms of its sound quality, ease of use and ease of editing.
Its popularity immediately spread to other areas such asrecording studios and movie sound recording.

Fig. 4.1. Mullin’s improved Magnetophon (1)Despite being a small-scale start-up company, Ampex Co.,
Ltd. was very interested in this demonstration and set aboutdeveloping its own model with a firm belief in its potential.
While it was difficult to set a direction and goals for thisproject to develop a completely new product, the company
was able to develop a playback head with advice from
Mullin. With positive cooperation from Mullin, such asproviding his own Magnetophon until the company was able
develop a drive train, the playback head developed by Ampex
did wonders for the performance of the Magnetophon. The
company then worked on other developments, such as arecording and a erase head, and managed to complete theAmpex 200 model by 1948 (Fig. 4.2). As pre-recorded
broadcasts began to dominate American airwaves, it wasFig. 4.2. AMPEX 200 (2)While Ampex developed the 200 model tape recorder, discrecorder manufacturers Audio Device and 3M appealed to
Ampex to provide information and guidance in developing
tape media. The Magnetophon had given these companies a
glimpse of the huge potential of magnetic recording, that is,
the tape recorder, in place of the disc recorder and they werevery interested in magnetic tape as a new product. While
3M had no experience with recording equipment, it was avery experienced chemical developer, and made a full-scale
entry into the field of magnetic tape, developing the famous“Scotch Magnetic Tape”. The company’s superior technicalcompetence enabled the production of magnetic tape thatoffered extremely stable performance for its time. It produced

Historical Development of Magnetic Recording and Tape Recorder197

the famous “Scotch 111”, which became the standard tapefor tape recorders all over the world (Fig. 4.3).

recordings of the national aquatics championships in Los
Angeles were brought to Japan by an NHK engineer and taperecorders began to be used in radio broadcasting in earnest.
From 1951, the post-war-founded commercial broadcasters
began to use the PT-6. Thus the Magnecorder was the firsttape recorder to be brought to Japan and put to practical use.
This machine provided much inspiration for domestic taperecorder development within Japan.

Fig. 4.3. Scotch 111 magnetic tape (3)4.1.3 Unified Standards
A great number of companies appeared in the United States
between 1947 and 1950, manufacturing and marketing taperecorders firstly as business machines used by broadcasters
and also for household use. While some of these were
well-established business equipment companies that had
been making disc recorders since the pre-war era, some ofthem were new players attracted by the new market. With
multiple manufacturers producing tape recorders according
to their own standards, there was little compatibility
between recorded tapes. This limited their scope of use
and presented an obstacle to the advancement of this longawaited technology. As tape recorders became more widelyused in broadcasting, this issue clearly worsened. Since radio
broadcasts had been popular in the pre-war days, there was an
association of commercial broadcasters in the United Statescalled the National Association of Broadcasters (NAB)*.
Given the use of sound recorders in broadcasting, the NAB
had already established the Recording and Reproducing
Standards Committee in 1941 for the disc recorders. In
1949, this committee extended its jurisdiction to regulate
the necessary terms, measurements and characteristics oftape recorders as well. The NAB standards became the defacto global standards for consumer use as well and were
implemented as national standards in many countries aroundthe world. This ensured a minimum level of compatibility inthe open-reel era.

4.1.2 Opposition to Ampex: the Magnecorder
While Ampex was working on developing the tape recorder,
several other US companies also began developing thisnew recording technology. While some companies became
interested after being inspired by Mullin’s demonstration of
the Magnetophon, others were working on developmentscompletely unrelated to the Magnetophon. Magnecord, aChicago company founded in 1946, introduced the SD-1
wire recorder as its first product and continued developing
new products. With a strong proposal from the sales end, thecompany put its steel wire development on hold and started
working on tape recorders. In May 1948, the company
exhibited its first prototype at the NAB Show, gaining
considerable popularity. This machine was called the PT-6
(Fig. 4.4) and was priced far lower ($499.50) than the Ampex
200 ($3,825). Its small casing also attracted more userinterest than the large, console-style 200. While the Ampex
200 had a three-head configuration allowing recordings to bemonitored for business use, the PT-6 was not really suitablefor business use, having only two heads: one for erasing andone for recording/playback. Two heads became the standard
configuration for household tape recorders, as cost was animportant factor and the two-head configuration offered thebasic recorder functions. Nevertheless, the Magnecorderswitched to three heads in 1950 to meet the demand for aproper business machine.

Fig. 4.4. Magnecorder PT-6 (1948) (4)In 1949, a Hawaiian Japanese radio station brought a
Magnecorder and some Scotch 111 magnetic tape to
NHK in order to record the popular amateur singing radio
programme “Nodojiman Shiroto Ongakukai”. In August thatyear, several Magnecorder PT-6s that had been used in relay

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* The National Association of Broadcasters, an associationof commercial broadcasters in the United States, wasestablished in 1923, having thus been in existence for
90 years. The NAB holds an annual convention in the
United States as well as world’s largest exhibitionsof broadcasting equipment (many of the recent
exhibitions have been in Las Vegas). The Recording andReproducing Standards Committee exists within theorganisation of the NAB. Following the Second World
War, this Committee set the standards for disc and taperecorders for broadcasting use and, together with the
RMA (later RTMA, now EIA), has long been known inJapan for these tape recorder standards.

4.2

Europe4.2.1 Revival of the Magnetophon
Although Germany was home to the advanced technologythat produced the Magnetophon, its defeat in the Second
World War left its magnetic recorders lagging behind. As anadvanced chemical product, magnetic recording tape had
been produced by the major chemical manufacturers and wasin frequent use by broadcasters for pre-recorded broadcasts in
pre-war Germany. After the war, the production of magnetic
recording tape in Germany was resumed by Agfa in 1949 and
BASF in 1950.
In 1954, nine years after the war, the freshly-outfitted
Magentophon M5 (Fig. 4.5) was finally released by
Telefunken, a subsidiary of AEG, for semi-professional use,followed by a model for home use in 1958. In 1952, AEG
released the KL-15D, a combined record player and taperecorder for home use. While the Magnetophon was thus
revived several years after the war, a significant portionof its tape recorder technology was publicly known andother European manufacturers who had previously worked
with steel wire recorders and other technology were now
developing their own tape recorders and putting them on themarket. The tape recorder was advancing across Europe as abusiness machine, with British company EMI producing the
BTR/1, a copy of the Magnetophon for professional use in1948 and Swiss company Studer producing the Dynavox forsemi-professional use in 1949.

post-war high-end tape recorder market together with US
company, Ampex. The Revox brand produced a successionof high-quality tape recorders for general use. The 36 series,
which originated in 1955 with the A36, had stereo capability
and continued to dominate the market through to 1967, whenmusic lovers and audiophiles fell for the sound quality of
the A77 (Fig. 4.7), considered to be the best general use taperecorder at the time. Despite being very highly priced, it was
extremely popular, with hundreds of thousands sold all over
the world.

Fig. 4.5. Magnetophon M5 (1954) (5)4.2.2 Activity by Studer
Studer was a small electronics manufacturer founded in
Zurich, Switzerland in 1948 by Willi Studer. Not longafter its founding, Studer began to import tape recorders
from the United States, inspiring the company to makeits own developments on the tape recorder. It started out
by remodelling the imported American tape recorders
to European specifications and completed its first taperecorder in 1949: the Dynavox. Although it was a smallscale company with limited human resources, equipment
and capability, it succeeded somewhat in business due tothe novelty of the tape recorder. With this experience under
its belt, the company improved its design and released theT26 in 1951, under the new brand name of Revox. While
the Dynavox and the T26 were developed and marketed
as general use (albeit highly-priced) tape recorders, Studer
developed the 27 model, based on the T26, as a tape recorderfor business use. This machine was trialled at music events
and was favourably received. In 1952, the Studer 27 went
into full-scale production (Fig. 4.6). Through the successof the Studer 27, the company gained a reputation as amanufacturer of business-use tape recorders, leading theHistorical Development of Magnetic Recording and Tape Recorder199

Fig. 4.6. Studer 27 (1952) (6)other areas also placed orders for the Nagra I, it was little
more than a prototype model and had a number of defects.
Kudelski completed the significantly-revised Nagra II (Fig.
4.8) and began to manufacture this model by the end of 1953.
Though portable, the Nagra had a very precise andtechnologically advanced tape operation system andpresented a wealth of possibilities to diversify the scope ofthe tape recorder. The Nagra III debuted in 1959; this model
had a systematic operation function, which could be usedin synchronisation with a cine-camera for cinematography,
for example. The Nagra continued to rank highly as thehigh-performance portable business machine of the taperecorder industry, used by film studios and broadcastingstations throughout the world. Brimming appeal withits maintenance-oriented design for business use, its
precisely-manufactured parts and the sharp, unique feel of
its operation, the Nagra became the landmark design formany tape recorder designers. As an integrated system witha number of peripheral devices for synchronisation withcinematography, it enjoyed a long reign as the main soundrecording equipment used on film sets. The Nagra’s rolein this industry finally came to an end as digital recording
equipment and digital voice processing rapidly replaced
analogue equipment.

Fig. 4.7. Revox A77 (7)4.2.3 A p p e a r a n c e o f “ N a g r a”, t h e Po r t a b l e Ta p e
RecorderWhile the tape recorder was a magnetic recording device
and relied more heavily on electrical systems than thegramophone, the major factors determining its performancein the pre-digital-recording era were the tape drive systemand the mechanism allowing accurate and stable operation. It
was a precision instrument requiring a high working accuracy
and an assembly system, so there was no better place for it
than Central Europe, where the watchmaking industry had
developed. Studer was founded in Switzerland, yet it wasanother Swiss company in Lausanne that produced a uniquerecorder exemplary of post-war Europe: the Nagra. Warsawborn Stefan Kudelski left his homeland of Poland during
the Second World War. He eventually settled in Switzerland
after living in Hungary and France. In 1951, in Lausanne,
Kudelski built a small, lightweight, portable tape recorderwith a focus on sound quality. He named this machine Nagra,
meaning “to record” in Polish. The first Nagra I was bought
by a local radio station in 1952. Although radio stations in

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Fig. 4.8. Nagra II (1953) (8)4.3

Development in Japan

4.3.1 D omestic Produc tion of Tape Recorders for
Business Use
Although Anristu and Nippon Electric Company (NEC)began to develop and manufacture steel wire recorders
around the late 1930s, they lacked development experiencein many areas, such as sound quality and operation; as aresult, they were not able to produce anything capable ofbeing used in broadcasting in the pre-war era. The fact that
NEC launched a steel wire recorder in 1948 indicates thatdevelopment had continued during the war; however, therecorder was not widely popular as it was very expensive (Fig.
4.9).

hand, while Totsuko adhered to the basic principles, it added
some of its own original technology.

Fig. 4.9. NEC MR-1 steel wire recorder (1948) (9)As mentioned in Section 4.1.2, the use of tape recorders inJapanese broadcasting started in 1949 with the American
Magnecorder. The PT-6 model used was brought to Japan byNHK. Using this model as a reference and with collaborationfrom NHK, Tokyo Tsushin Kogyo (“Totsuko”, later Sony)and Nippon Denki Onkyo (later Denon) started working
on a domestically-produced tape recorder. Development
had finally begun on a Japanese-made tape recorder. Denon
was an established company with various achievements
as a domestic manufacturer of recording equipment forbroadcasting both before and after the war, including
supplying disc-style recorders to NHK. Its roots were in the
Denki Onkyo Research Institute founded by Koichi Tsubota
before the war to work on domestic disc-style recorderproduction. Tokyo Tsushin Kogyo, on the other hand, was a
new company, founded by Masaru Ibuka in 1946, that had
developed and marketed several measuring instruments forelectrical engineering and was constantly looking to workon innovative new products. Respective company founders
Tsubota and Ibuka were contemporaries at the Waseda
University Faculty of Science and Engineering, although it is
not known to what extent the two men knew each other.
Both companies built prototype tape recorders within ashort space of time (Figs. 4.10, 4.11), which were thenevaluated by NHK. The results of this evaluation werereflected in the official demands that were submitted, while
the prototypes were redesigned to meet NHK specifications.
The prototypes were introduced by NHK in 1951 as the PT11 (Fig. 4.12) and PT-12 (Fig. 4.13), the first domesticallyproduced tape recorders for business use, and were put touse by broadcasting stations all over Japan. It seems that themachines were treated as “portable”, with the tape transporterand amplifier each in separate casings. Photographs of the
prototypes show the differences in approach between thetwo companies. Denon, with its wealth of experience inthe field of broadcasting equipment through its disc-style
recorders, was trying to emphasize guaranteed performanceand credibility in the field of business machines by making afaithful reproduction of the Magnecorder PT-6. On the otherFig. 4.10. Totsuko Prototype No. 1 (10)Fig. 4.11. Denon Prototype No. 1 (11)Fig. 4.12. PT-11 Totsuko (12)Fig. 4.13. PT-12 Denon (13)Historical Development of Magnetic Recording and Tape Recorder201

4.3.2 The Creation of Prototype No. 1 by Totsuko
From the outset, researchers at Tokyo Tsushin Kogyo werevery interested in magnetic recording and had studied
systems such as the steel wire recorder. Coming into contact
with the tape recorder through the NHK, the researchers
were convinced of the potential of this new product andconcentrated their efforts on developing it. Despite theextreme scarcity of reference material, Totsuko showed
incredible manoeuvrability for a start-up company headed
by engineers, repeating a number of designs and prototypes
in a short space of time. It seems the company was also
examining and investigating the principles of magnetic
recording, while its procurement of the purportedly
indispensable “high frequency bias patent” from Anritsu
indicates that it was preparing to ensure the superiority of
its products through its unique technological developments.
Having abandoned the early steel wire recorders in favourof the tape recorder in its work on magnetic recording,
Totsuko worked on its own developments in spite of various
hardships. While its first prototype was for the NHK, as
mentioned in the preceding paragraph, the development of
products for business use definitely contributed greatly tothe company’s accumulation of technology. Although thescarcity of parts and materials and the lack of informationand technology following the war meant that new productdevelopment was rife with difficulties, Totsuko finallyreleased the “G” in 1950, the first domestically-produced taperecorder. At ¥160,000, it was very highly priced. Althoughtape was also being developed and marketed, it was still the
rudimentary paper-based tape. The physical properties ofthis tape, such as its smoothness, were still underdeveloped,
which directly affected the recording and playback functions(Fig. 4.17).
A major obstacle to Totsuko building a tape recorder was thelack of appropriate parts. In particular, the driving motor had
to rotate at a constant speed; it had to be silent (a matter ofcourse for sound equipment); it had to produce a certain levelof torque. These criteria could not be met with the motors
from general electrical goods, such as fans, so the company
asked Denon for the use of its hysteresis synchronous motor
developed for use in disc-style recorders.
The company also had much difficulty finding a good rubbermaterial to use for the power transmission unit idler and inother parts. Totsuko built up a diverse wealth of knowledge
to improve the rubber belts and idlers, which later proved
very useful in improving the performance of the Sony taperecorder, ensuring its predominance.
Another major challenge was developing the magnetic tape.
The researchers understood that coating a base material withmagnetic powder would produce a tape that could be used
for recording, but, with very little in the way of referencematerial, they were blindly guessing as to what they could

use, both for the base material and for the powder coating.
With the idea of simply proving the tape was magnetised,researchers ground cylindrical OP magnets into powder in amortar and tried coating this onto a suitable paper material
with a paste made from boiled rice. This experimental
tape produced only noise. After various experiments, theresearchers concluded that the ground-up magnets were
too strong and that they should use a weaker magnet forrecording. The use of powdered OP magnets as a magnetic
substance was the same method used for the later metaltapes, but perhaps the level of technology at the time meantthat the heads were not able to magnetise a highly coercive
magnetic substance. The Totsuko research team searchedthrough various sources of literature and found that if asubstance called ferric oxalate is oxidised by burning, it
becomes ferric oxide. Despite the lack of materials, they
managed to acquire a ferric oxalate reagent and immediately
set about heating it in a frying pan. The yellow ferric oxalate
turned brown and then black; by observing the colour andtaking it off the heat at the appropriate time, they were able
to produce ferric oxide powder without any problem. To
coat this powder onto the base material, they started out
by using a spray gun, but this wasted a lot of the powder.
Through trial and error, they ended up creating a prototype
by applying the powder with a brush. They made repeatedrecording experiments on a primitive experimental recording
device made from a pair of 78 RPM record turntables. They
improved the magnetic substance and made various analysesof different choices of base material, but at that time there
was no paper or plastic in Japan suitable for use as magnetic
tape. They had no choice but to leave it to a paper expert andenlisted the help of Honshu Paper Co., Ltd., which showed agreat deal of interest in the development of the new product,
as it could potentially supply the base material for the paper
tape (Figs. 4.14, 4.15). Following these developments on themagnetic tape and the machine itself, the “G”, Japan’s firsttape recorder, was released in 1950.

Fig. 4.14. Tools used for the magnetic
tape prototype (replicas)

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develop the product to try to lower the price and increase its
ease of use. With technology, patent strategies and marketingas its weapons of choice in the popularity stakes, Totsuko
was laying the groundwork for it to become Japan’s leading
tape recorder manufacturer.

Fig. 4.15. Prototype tape (1949)

Fig. 4.18. Totsuko tape recorder manualFig. 4.16. The Totsuko G, Japan’s first domesticallyproduced tape recorder (1950) (14)Fig. 4.17. Early “Soni-Tape” made by Totsuko (1950) (15)4.3.3 Marketing Tape Recorder No. 1
Totsuko started marketing the G under the trademark“Tapecorder”. Although customers were interested in
the novelty of it, it was not readily accepted as a generalhousehold item, as it was expensive, big and clumsy,
with no obvious usefulness. It was mainly used by publicorganisations, such as for recording courthouse proceedings.
This was what had been foreseen, with even the letter G
standing for “government”. Totsuko started out marketing in
the belief that the popularity of this ground-breaking productwould also spread to household use as well. However,
although there was some interest in the product, this interest
did not really translate into sales. Totsuko reviewed its rather
optimistic policy of “if we build a good machine, it will sell”
and focused its attention on raising public awareness andadvertising the tape recorder, creating a manual to explain
the uses and benefits of its top tape recorder and redoublingits sales activities (Fig. 4.18). The company also continued to

4.3.4 Totsuko and the AC Bias Patent
As mentioned in Section 3.6, AC bias was discovered bychance in the 1920s during research on magnetic recording,but it was not until the late 1930s that research began
in earnest throughout the world on how to improve theperformance of magnetic recording. This coincided exactlywith the start of the Second World War. Since recording
technology had definite useful military applications, suchas broadcasting and voice recording, the exchange oftechnology between countries was stopped until after thewar. After Germany’s defeat, the Magnetophon – the mostadvanced technology of the day – was taken and studied
in detail by the victors. As a result of the ensuing rapid
technology transfer, better, more modern tape recorders weredeveloped and put to use. AC bias came to be recognised
as an indispensable piece of technology for high quality
recording and playback.
Totsuko began developing the tape recorder in Japan after
the war. As well as making its own tape, it also set aboutcarefully examining relevant patents on AC bias, having
found that AC bias was necessary in order to be able tocommercialise the tape recorder. The patent for AC bias inJapan had come about as the result of research by Kenzo
Nagai of Tohoku University and Teiji Igarashi, one ofNagai’s assistants who had continued the research at Anritsu
Electric. The patent rights were held by Anritsu (Fig. 4.19).
After negotiating with Anritsu, Totsuko took over the patentrights for AC bias in October 1949. As this was a hugeinvestment for Totsuko at the time, the company bought thepatent jointly with NEC. The Nagai Patent had been granted
in Japan in 1940. Although a US patent had also been appliedfor, the procedures had been interrupted by the war. In themeantime, the Camras Patent had been established as thepatent for AC bias in every other country except Japan.

Historical Development of Magnetic Recording and Tape Recorder203

Nagai Patent
Teiji Igarashi, Makoto Ishikawa, Keizo Nagai
A Magnetic Recording System Using AC for Bias
Patent No. 136997; applied for in March 1938;
granted in June 1940.

Fig. 4.20. Akai AT-1 tape mechanism (17)

1. Recording medium
2. Demagnetisation/
erasure coil
3. Recording coil
4. Microphone

5. Recording amplifier
6. High frequency
source for biasing
7. Playback coil
8. Playback amplifierFig. 4.19. Partial drawing from the “Nagai Patent” on AC bias (16)4.3.5 Dispute over the AC Bias Patent
The domestic Japanese tape recorder market developed
rapidly from the launch of the G in 1950. The AC bias patent
proved to be a major weapon for Totsuko to keep othercompanies out of the marketplace, enabling the company
to hold on to its high market share in tape recorder sales.
Around this time, the US trading company Balcom began
large-scale import and sale of US-made tape recorders
in Japan. Totsudo and NEC complained that this was an
infringement of their AC bias patent rights and repeatedlyissued Balcom with requests to either pay royalties orstop selling. Balcom repeatedly ignored them, so Totsukopresented its case to Tokyo District Court in September
1952. This turned into a major case for Balcom, involving
even the GHQ, but Totsuko eventually won the case. During
the course of the proceedings, the US patent holder, Armour
Research Foundation, came to Totsuko’s attention. Thinking
that its exports might be affected, Totsuko reconciled withArmour and the two entered into an agreement of mutualtechnological assistance.
Totsuko stood firm on patent permission with regard to
Japanese manufacturers as well. In 1954, Akai ElectricCompany launched a tape recorder kit featuring a “new AC
bias method”, which ingeniously incorporated a bias circuit(Fig. 4.20). Totsuko immediately objected that this was apatent infringement, but Akai Electric denied this as it “didnot violate the Nagai Patent”. Although the matter went
to court, Totsuko decided to reach a settlement, in light of
its isolation in the industry as well as other circumstances.
Nevertheless, fierce competition continued in productdevelopment.

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With the Nagai Patent licence due to expire in 1955, many
manufacturers, including major electrics companies, were
anticipating getting involved in the tape recorder industry.
However, the patent licence was extended for another five
years on the grounds that the patent was not able to be put
to use during the Pacific War. A number of companies that
had been making preparations to enter the industry clearly
opposed Totsuko and the Ministry of International Trade andIndustry. Although Totsuko continued to refuse to licence thepatent rights, by 1958 the manufacturing latecomers were
granted consent to use the Nagai Patent. Fierce competition
ensued in the development and marketing of new products,
and Japan’s tape recorder industry was making tremendous
leaps forward.

References
1)

Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono
10 [The Story of the Tape Recorder 10]”, JAS Journal
2005, Vol. 45, Nos. 8 & 9.

2)

Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono
5 [The Story of the Tape Recorder 5]”, JAS Journal
2005, Vol. 45, No. 1.

3)Mori, Yoshihisa, et. al. Onkyō-Gijutsu-Shi [History ofSound Recording], Tokyo University of the Arts Press,
March 2011, p. 81.

4)Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono
8 [The Story of the Tape Recorder 8]”, JAS Journal
2005, Vol. 45, Nos. 5 & 6.

5)Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono
24 [The Story of the Tape Recorder 24]”, JAS Journal
2007, Vol. 47, No. 4.

6)Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono
25 [The Story of the Tape Recorder 25]”, JAS Journal
2007, Vol. 47, Nos. 5 & 6.

12) Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono

7)

Provided by Mori, Yoshihisa.

8)Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono

37 [The Story of the Tape Recorder 37]”, JAS Journal

28 [The Story of the Tape Recorder 28]”, JAS Journal

2008, Vol. 48, Nos. 11 & 12.

9)

2007, Vol. 47, No. 10.

13) Ibid.

Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono

14), 15) Provided by Sony Corporation.

36 [The Story of the Tape Recorder 36]”, JAS Journal16) Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono

2008, Vol. 48, No. 10.
10) Provided by Sony Corporation.

32 [The Story of the Tape Recorder 32]”, JAS Journal
2008, Vol. 48, No. 4.

11) Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono

17) Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono

36 [The Story of the Tape Recorder 36]”, JAS Journal

41 [The Story of the Tape Recorder 41]”, JAS Journal

2008, Vol. 48, No. 10.

2009, Vol. 49, Nos. 5 & 6.

Historical Development of Magnetic Recording and Tape Recorder205

5 Development of Domestically-Produced Tape Recorders
5.1

The Popular-Model Tape Recorder

Having completed the G, the first domestically-produced
tape recorder, in 1950, Totsuko launched the popular-model
H (Fig. 5.1) in 1951, aimed at popularising the tape recorder.
At ¥84,000, it was around half the price of the G. With asimple mechanical configuration of a single motor and twoheads, it was also ingeniously designed to be easier to use,such as having a single knob to switch the tape operation
and amplifier between recording and playback. The entire
machine was stored in a trunk-like case, which showed thatsome consideration for household use had been incorporated
into its design. In fact, the H was the first model for which
Totsuko employed an industrial designer. In 1952, a year after
the H, Totsuko launched the even lower-priced P (¥75,000)(Fig. 5.2). The main customers of both the H and the P wereelementary and junior high schools as the machines werestill too highly-priced for household use. Although Totsuko
redoubled its marketing through advertising and publicawareness, the tape recorder remained a largely unknown
device in domestic circles.However, its capacity to enrichaudio-visual education was being hailed in schools. With
its scope of use thus expanded, it was only a matter of time
before the school pupils made it commonly known about at
home. Totsuko released the R in 1953 at a price of ¥50,000.
The following year, it marketed the TC-301, an improved
version of this model, as a “small machine for home use”.
Although this model was simpler than the H and P models
in terms of performance, the tape recorder began to spreadthrough ordinary households in earnest thanks to the onset ofmass production and mass marketing of low-priced products
around this time.
The speed of product development also increased; in
1954, the TC-302 – the deluxe version of the TC-301 –hit the market at ¥57,000. The following year, in 1955,
Totsuko produced a succession of products as the leading
tape recorder manufacturer, such as the premium TC-501(¥84,000) and the two-channel TC-551 (¥135,000), capableof recording in stereo. In 1956, Totsuko released the TC201 at the drastically-reduced price of ¥38,000, throwing

Table 5.1. Early Totsuko Tape Recorders(4)Model No.

P-3

TC-301TC-302TC-501

TC-551

TC-201TC-401

Release date and1954(S29).10

1954(S29).09

1954(S29).12

1955(S30).09

1955(S30).12

1956(S31).07

1956(S31).08

price

69,50049,00057,00084,000135,000

38,00065,000External dimensions (mm)(¥)

250×400×300

170×300×300

190×320×300

220×490×360

240×690×430

220×420×335

210×420×330

Weight

(kg)

14

8

8.3

15

27

12.3

14

Maximum reel

(in)

7

5

←

7

←

←

←

Tape speed(cm/s)

19, 9.5

9.5←

19, 9.5

←

←

←

Heads

(no.)

2

←

←

←

←

←

←

half width

←

←

←

full width erase

half width

←

Track

two-channel・R/P
Motors

(no.)

2

1

←

←

←

←

←

Speakers

(in)

6.5

5

5×7

←

5x7 (x2)

4×6

5×7

Microphone(ohms)

10k

←

←

←

×2

10k

←

50〜10,000Hz

70〜10,000Hz

150〜7,000Hz

50〜10,000Hz

Frequency response (19 cm/s) 100〜7,500Hz(9.5cm/s)←

100〜6,000Hz←

200〜4,000Hz

100〜6,000Hz

SN ratio

(dB)

40

40

40

50

50

40

45

Wow-and-flutter

(％ )

0.5

0.5

0.5

0.25

0.25

0.3

0.25

Bias

(kHz)

30

←

←

50

←

30

50

6AU6×2, 42.80

6AU6×2, 6AR5

6AU6×2, 6AQ5

6AU6×2, 12AU7

6AU6×2, 12AU7×2

6AU6×2, 6AR5

12AT7×2, 6AQ5

6×4

6×4, 6E5M

6 A R 5 ×2 ,5GK4

6AQ5×2, 6AR5

6×4

6AR5, 5GK,
6E5

Valves206

150〜5,000Hz

6E5M

6E5M×2, 5Y3GT

Power source

AC100V

←

←

←

←

←

←

Power consumption (W)

100

60

75

100

140

60

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the popular-model tape recorder market wide open (Table
5.1). Although Totsuko had achieved success with the taperecorder, it was always watchful of developments among
the major manufacturers because of its own relative lack of
capital might. It took great care to ensure the predominanceof its own products by improving its product development
capabilities and exploiting its AC bias patent.

Fig. 5.3. TC-551 Stereocorder (1955) (3)5.2(1) Motor(6) Recording/playback head(2) Motor axle
(7) Capstan(3) Reel axle (winding) (8) Switchover camshaft(4) Reel axle (feeding) (9) Pushbutton(5) Erasing headFig. 5.1. Totsuko H and an outline of its mechanism (1951) (1)Fig. 5.2. Totsuko P (1952) (2)Increase in Manufac turers Entering
the Market

While Totsuko obstinately refused permission for othercompanies to use the Nagai Patent for AC bias, things
eventually began to change in the industry, such as Akai’s
insistence that its “new AC bias method” was not a patent
infringement. This occurred around 1955, just when thedispute with Balcom and Armour had reached a conclusion(See Section 4.3.5). Although the regulatory authority, theMinistry of International Trade and Industry, had initially
supported Totsuko’s position in the dispute with Balcom, it
did have some misgivings about obstinate patent right claims
in terms of industry development. Totsuko had taken great
pains to ensure the predominance of its successful new taperecorder so that it could ensure enough capital to develop thetransistor radio. However, Totsuko also recognized that to adegree it had already profited as a founding member of theindustry, that competition was an inevitable factor in market
expansion, including the export market, and the company
was by now confident in its product development ability. In
the light of this and other factors, in 1958 Totsuko decided toallow other Japanese manufacturers to use the Nagai Patent,
provided that it was through Totsuko and NEC.
This meant that the AC bias method required for analogue
tape recorders was freely available for use (albeit withlicence fees payable). More than ten companies started
manufacturing tape recorders for consumer use, including
Matsushita Electric Industrial, Sanyo Electric, Toshiba,
Tokyo Electro Acoustic Company (later TEAC) and Yaou
Musen (later General). Matsushita began research anddevelopment very early on at its central research institute.
It took the lead among the latecomer manufacturers,
releasing its RQ-201 (Fig. 5.4) in August 1958, right after
the patent licence was granted. This set was manufactured
by Matsushita Communication Industrial; a number of setsmanufactured by Matsushita Electric Industrial proper werereleased in December the same year.

Historical Development of Magnetic Recording and Tape Recorder207

Fig. 5.4. Matsushita No. 1 RQ-201 (1958) (5)5.3

Tape Recorders for Use in Education

After the war, the Ministry of Education set about promoting
audio-visual education at the request of the GHQ, leasing
16mm projectors to elementary and junior high schools allover the country, among other initiatives. The NHK tookcharge of audio resources and started full-scale educational
broadcasts for schools. This course of events gave a major
boost to the popularity of the tape recorder and gave rise toa growing demand for tape recorders in schools. However,
the early tape recorders were extremely variegated in termsof operation, specifications and terminology and there wasno compatibility whatsoever between them. To rectify this,a motion was drafted by the NHK Science & ResearchLaboratories and enacted by the Ministry of Education in
1954 to specify the basic standards for the features requiredin tape recorders for educational use. The main details are
given below.
(1)	G eneral Rules: definition of a tape recorder for
educational use(2)	Configuration: Mechanism requirements(3)	Standards and special conditions
1) Various performance standards and standard tape2) Level indicator and standard recording level3) Recording track positioning: compatibility assurance4) Overall sound characteristics(4)	Insulation tests and pressure tests(5)	Product labelling and associated books
Popular-model tape recorders with built-in speakers,
produced in Japan in accordance with these standards, went
on sale from around 1955. At the same time, a variety ofsimilar tape recorders from the West and other overseas
countries were imported and sold domestically (Fig. 5.5).
While the tape recorders for educational use (in schools)
came down in price, they were quite bulky and seemed very

208

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012much like business equipment; the smaller, more portabletypes were more popular for home use. The machines forschool use had standard reel sizes from No. 7 (18cm) to
No. 10 (27cm), while the machines for home use ranged
from No. 5 (12cm) to No. 7. While a longer recording time
was afforded by having as long a length of tape as possible
on a reel, the price of the tape was a major factor for homeuse. To economise on tape consumption, a tape speed of
4.8cm/s was added to the existing standardised speeds of
19cm/s and 9.5cm/s. With the advent of the 1960s, popularmodels emerged in great numbers at greatly reduced prices.
The demand also grew for tape recorders for studying at
home (Figs. 5.6, 5.7). The time for great numbers of smallto-medium manufacturers in the industry had ended. The
time had come for major manufacturers to take on the taperecorder in earnest, producing far superior machines. Therewas much competition between the popular models made bymajor manufacturers. Matsushita released the RQ-303 (Fig.
5.8), which used a dedicated No. 4 reel (10cm) and a tapespeed of 4.8cm/s to make it smaller and more lightweight.
At ¥10,000, around half the price of other machines inthe same class, it was a major hit. In 1958, Tokyo Tsushin
Kogyo changed its name to Sony Corporation, with the ideathat merging the company name and product name would
reinforce the brand name.

Fig. 5.5. TK-9, made by West German company Grundig (8)Fig. 5.6. Toshiba GT-620 “College Ace” (¥18,800) (7)Fig. 5.9. Denon disc-style recorder used in“man-on-the-street” interviews (10)Fig. 5.7. Sony TC-111 (¥19,800) (1961) (8)Fig. 5.10. Stancil-Hoffman “Mini-Tape” (11)Fig. 5.8. Matsushita RQ-303 “Mysonic” (¥10,000) (1963)

5.4

(9)

Emergence of “Densuke”

In 1946, right after the war, the NHK started broadcastingso-called “man-on-the-street” interviews, run by announcer
Shuichi Fujikura. The novelty of these “audience
participation programmes”, in which the ordinary people
became part of the cast, as well as the interviews on current
public opinions, made these programmes very popular. At
first, the NHK used the disc-style recorder (Fig. 5.9) that had
been used in broadcasting since before the war. Although
it was portable, it was heavy, susceptible to vibration, therecords had to be changed over due to the limited recording
time on each disc and the recording level had to be constantly
adjusted. These factors would have made it very difficult to
operate in the street.

Around this time, portable tape recorders were being
introduced from the United States. In 1951, the NHK began
to use these for its “man-on-the-street” interviews. The
model used was the shoulder-strap-style “Mini-Tape” madeby Stancil-Hoffman (Fig. 5.10). Equipped with a No. 5 reel,
this machine was capable of two speeds of 38cm/s and 19cm/
s. The DC motor rotated in sync with an internal vibrating
oscillator (details unknown) as part of a drive system toproduce a steady revolution speed. It was a dedicatedrecording machine, with the built-in valve amplifier onlyused for basic recording, although a small external amplifier,sold separately, could also be attached for monitoring. When
Nobutoshi Kihara of Totsuko heard about this machine,
he started investigating similar machines, referring tophotographs and other reference materials, without everhaving seen the machine itself. In March 1951, he started ona prototype, which he supplied to the NHK in July that year
(Fig. 5.11). Despite the fact that he had the Mini-Tape to refer
to, it is actually quite remarkable that he developed a working
prototype in such a short space of time. It was configured
quite simply with a valve amplifier dedicated to recording,a single recording head and no erasing head. Although
this meant that the recording tape had to be demagnetisedin advance, it was well received as a recording device forprofessionals, who actually preferred simplification if it
ensured reliability. While the tape operation system anddrive system resembled those of the Mini-Tape, no suitable

Historical Development of Magnetic Recording and Tape Recorder209

(1) Rewinding 5-inch reel(9) Zenmai tension indicator(charger plug for M-2)
(2) Rewinding tape guide(10) Recording-playback switch(3) Pinch roller(4) Capstan(11) Microphone connector(5) Winding 5-inch reel(12) Oscillation signal light(6) Handle shaft hole for rewinding(13) Listening receiver jack(7) Recording/playback head
(14)
Volume controller(8) Start/stop power switch

Fig. 5.11. Photograph and exterior diagram of Totsuko M-1 (1951) (12)DC motor could be procured domestically in those days.
Kihara eventually settled for a hand-wound spring motor forgramophones (a Zenmai motor), made by Nippon Columbia.
Fully wound, the spring motor could drive the machine foraround four minutes. Ingeniously, Kihara incorporated an
additional winding mechanism that enabled a No. 5 reel tooperate continuously for 15 minutes.
Having introduced the Totsuko shoulder-strap-style recorder,
the NHK was immediately able to boost the manoeuvrabilityof its “man-on-the-street” interviews, which in turn boosted
the popularity of its programmes. Ryuichi Yokoyama turned
these “man-on-the-street” interviews into cartoon form
with his “Densuke” character that appeared in the Mainichi
Shimbun. The Totsuko tape recorder came to be known as
the “Densuke”, based on this character, roaming the streetswith his tape recorder on his shoulder doing “man-on-thestreet” interviews about current events. In the broadcasting
industry, this nickname came to be used to refer to outdooruse recording machines.
Totsuko registered the name Densuke as a trademark, using
it as a pet name for its portable tape recorder. Although thename remained in popular use between professionals in theindustry, it was soon forgotten in the everyday tape recorderworld. However, the name once again gained popularity as
the pet name for everyday tape recorders (see Section 6.11)
when the “Cassette Densuke” TC-2850SD portable cassettedeck (Fig. 5.12) appeared in 1973 along with a boom in live
recording. Later, the Open Densuke (Fig. 5.13) and Elcaset
Densuke (Fig. 5.14) appeared and the name Densuke became
synonymous with the highly-portable tape recorder in theeveryday tape recorder world.

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Fig. 5.12. Sony TC-2850SD (1973) Cassette Densuke (13)Fig. 5.13. Sony TC-5550-2 (1974) Open Densuke (14)Fig. 5.14. Sony EL-D8 (1977) Elcaset Densuke (15)5.5

Ultra-Small Magnetic Recorders
Fig. 5.16. The Midgetape and its special tape cartridge (1955) (17)With its success in the domestic production of a shoulderstrap-style tape recorder, which had been adopted by the
NHK as well as other commercial broadcasters, Totsuko set
about researching and developing an even smaller magnetic
recorder. An ultra-small magnetic recorder called the Minifon
had been developed and marketed in Germany in 1952 (Fig.
5.15). This was a wire recorder with 0.05mm steel wire as
its recording medium and its minute mechanism containedin a tiny casing. It was configured with precise detail, with
forethought given to ease of use and stable operation. It
could record, playback and rewind; appropriate tension on
the wire at all times prevented it from breaking or jamming.
In 1955, a magnetic recorder called the “Midgetape” (Fig.
5.16) appeared in the United States, based on the concept of
the Minifon. This was a uniquely-configured, ultra-small taperecorder that used a cartridge-style tape with two tiny reels ina casing.

The Totsuko SA-2 Babycorder (Fig. 5.17) hit the market
in 1957, probably based on these models. With the aimof becoming ultra-small and lightweight yet maintaining
performance, it incorporated a transistor amplifier. Equippedwith a cartridge like the Midgetape and operated with ten
AA batteries, it was small in size and easy to use. Moremobile than the M model, it was supplied in great numbers to
broadcasters and other organisations. However, it disappeared
off the market within a few years, as it was too highly
priced at over ¥100,000 to become popular in general use.
Nevertheless, Totsuko’s commitment to developing smaller,
lightweight models became typical of later development
trends in the consumer electronics industry.

Fig. 5.15. External and internal viewsof the Minifon (1952) (16)Historical Development of Magnetic Recording and Tape Recorder211

Fig. 5.17. Sony SA-2 “Babycorder” (1957) (18)

5.6

Battery-Operated Tape Recorders

Around 1959-1960, export manufacturers began to makelarge quantities of “reel-driven” battery-operated taperecorders, in which the tape was driven only by the rotationof the reel. While these could be regarded as copies of areel-driven tape recorder made by a German manufacturer
in 1958, they were mainly made for export to the UnitedStates, being quite simple in construction and relatively easy
to manufacture. The reel-driven machines had no capstan tomove the tape at a constant speed; they simply recorded byrotating the winding reel at a fixed revolution and thus could
be built with a very simple mechanism. However, since thetape speed changed from the start of the tape to the end of thetape, recordings could only be played back on the machineon which they were recorded (self-recording) and were
not compatible with any other machine for playback. The
variation in recording and playback performance from thestart of the tape to the end of the tape also meant that it wasdifficult to develop this into a high-quality recorder. Thesetape recorders never appeared on the Japanese domestic
market. With their simplified performance and low price,
many of them were little more than toys.
Meanwhile, proper battery-operated, capstan-driven, portable
tape recorders gradually grew in number. By the mid-1960s,
tape recorders were well-established in the export market,
although the simplistic, reel-driven models had disappeared.
This led Japanese manufacturers to work on the compact
cassette style tape recorder. Sony launched its battery
operated, portable tape recorders, such as the performanceenhanced, capstan-driven SA-2 Babycorder for business use
and the tiny TC-902 for personal use, but they did not always
meet with success.
Matsushita Electric entered the tape recorder market in 1958,

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but could achieve no definitive advantage over industry
leader Sony (Totsuko). Matsushita determined to establish
its own place in the market, setting its sights on the batteryoperated tape recorder, which Sony had not yet mastered.
In those days, the greatest obstacle to battery operation was
the lack of good quality, small-scale DC motors. With thehelp of its battery and device departments, Matsushita set towork on basic component development, such as simplifying
mechanisms and improving motor efficiency. In December
1960, it completed the RQ-112 (¥37,500). The following
year in 1961, it launched the improved RQ-114 model, laying
the foundation for battery operated, portable tape recorders
and leading to the best-selling RQ-102 in 1965. Motivated by
the developments among the latecomer manufacturers, Sonylaunched the TC-800 (¥36,000) in 1966 (Fig. 5.19), with abuilt-in, direct drive servo motor. Development competition
grew increasingly fierce among the major manufacturers,
ushering in the compact cassette era.

Fig. 5.18. Sony TC-902 (1959) (19)

when stereo FM broadcasts started in earnest around 1970,
tape decks grew tremendously in popularity as a means forrecording these broadcasts.

Fig. 5.19. Sony TC-800 (1966) (20)

5.7

Fig. 5.20. Staggered head placement (21)Development in Func tion and
Performance

5.7.1 Stereo Conversion
Tape recorders enable multiple-track recording on the sametape. In principle, it is very simple to create the stereo effect.
While disc records were the mainstream medium of themusic industry, the question of how to record (cut) and playback a single sound as two signals presented a very difficult
problem. In 1931, British electronics engineer Alan Blumlein
patented the idea of a 45/45 system to record separate signals
from the left and right walls of the groove in a record,
although this was not put into practical use until after LP
records appeared in 1958.
While magnetic stereo recording experiments had been
carried out in 1939 on steel wire recorders, the two-trackrecorder released by the US company Magnecord in 1949
was the first tape recorder to incorporate stereo sound. The
head placement was the so-called staggered type (Fig. 5.20),
where the two channels are set slightly apart from each other.
Given the head manufacturing technology available at thetime, it was difficult to achieve the manufacturing precision
required to have two tracks on one head; there was no choice
but to have a separate head for each track. By the late 1950s,
many stereo tape recorders were being sold in the UnitedStates, including machines for home use. Rapid progress wasmade on the speaker-less “stereo tape deck”, as it could be
used in the home in conjunction with other audio equipment.
It was easy to use because it worked on the same machine asa record player and the cost was relative to the improvementin performance. Advancements were also made on headtechnology, and the stacked arrangement (Fig. 5.21) soon
replaced the staggered. Although stereo tape records (music
tapes) grew in popularity as the stereo playback media of
choice in the home, they quickly lost their top spot in themarket when the cheaper stereo LP records went on sale.
Stereo tape recorders had a slow start in Japan, althoughFig. 5.21. Stacked head placement (22))

5.7.2 Transistors
To begin with, all tape recorder amplifier units used valves,
but with the increasing use of the transistors in electronicequipment, researchers began examining their application intape recorders. In 1959, Hyfax incorporated transistors into
its TR-100S stereo tape deck; however, it went off the market
almost immediately as the product was somewhat imperfect:
the transistor is a difficult component to get right, producing
a lot of unwanted noise and causing the amplifier to behave
erratically.
Accordingly, the first proper transistor tape recorder inJapan was the TC-777 (Fig. 5.22) produced by Sony in1961. Although it was monophonic, the TC-777 was a semiprofessional, high quality machine with three heads, three
motors and electronic operating buttons. It also had builtin power amplifiers and speakers. It was very popular with
its extremely high cost performance, and was outstanding indesign as well. Its successor, released in 1964, was a stereo
tape deck. From then on, there were rapid advancementsin the use of transistors in tape recorders and this becamea feature of battery-operated, small-scale compact cassette
players.

Historical Development of Magnetic Recording and Tape Recorder213

2007, Vol. 47, Nos. 8 & 9.
7)

50 Years of Audio. Japan Audio Society Publishing,December 1986, p. 476.

10) Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono
39 [The Story of the Tape Recorder 39]”, JAS Journal
2009, Vol. 49, Nos. 2 & 3.
11) Ibid.
12) Ibid.
16) Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono
Fig. 5.22. Sony TC-777 (1961) (23)

References
1)

Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono
41 [The Story of the Tape Recorder 41]”, JAS Journal

2009, Vol. 49, Nos. 11 & 12.
17) Ibid.
21) 50 Years of Audio. Japan Audio Society Publishing,December 1986, p. 481.

2009, Vol. 49, Nos. 5 & 6.

22) Ibid.

3)

Ibid.

2), 8), 13), 14), 15), 18), 19), 20), 23) Provided by Sony

4)

Ibid.

6)

Abe, Yoshiharu. “Tēpu Rokuon-ki Monogatari Sono
27 [The Story of the Tape Recorder 27]”, JAS Journal

214

45 [The Story of the Tape Recorder 45]”, JAS Journal

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

Corporation.
5), 9) Provided by Panasonic Corporation.

6 Emergence of Cartridge-Type Tape Recorders
6.1

Characteristics of the Open-Reel
Tape Recorder

The first proper tape recorders began to appear after the war
and rapidly replaced the disc-style recorder. By the 1960s,
tape recorders were the first choice of recorders from business
use to home use. They became indispensable equipment forbroadcasters and recording studios and were well-received
in other industries, such as music production, where multitrack recording enabled new musical works to be created.
The superior features of the tape recorder mesmerised many
audiophiles and it now became a popular piece of household
audio equipment. However, from the beginning, these taperecorders were all “open-reel” machines that needed reelsof tape to work. In order to maintain high quality, open-reeltape recorders had to have a high tape speed, which used up a
lot of tape. This meant that the reels and the overall machine
had to be quite large in size. Of course, there were smallermachines, but many of them had to compromise on featuresor recording time. The fact that these tape recorders neededreels of tape to work meant they were difficult for the average
person to use. People ran into various difficulties, such as
the tape on the reels being damaged by careless treatment,or the tape coming unwound and jamming. Although studies
on using the tape in a cartridge (case) as a way to overcome
these shortcomings had been made quite early on after thewar, nothing practical had eventuated from these studies.

6.2

RCA Cartridge

Stereo tape decks came into popular household use as ameans of stereo playback from around the mid-1950s in the
United States. Quite a number of music tapes went on themarket around this time as well. Although the 45/45 stereo
LP record became quite popular after it hit the market in
1958, the stereo tape recorder remained the main item ofhousehold audio equipment in the United States until the
mid-1960s. Given the popularity of music tapes, RCA set
about researching cartridge-style tape recorders quite earlyon. In 1958, RCA Victor announced its cartridge-style tape(Fig. 6.1) and put around 150 kinds of music tapes on salealong with the tape recorder. Measuring 184×120×12mm,
the cartridges were larger than the compact cassettes thatwould later emerge. The tape was 6.3mm in width, the sameas that of the open-reel machines, while being 25μm thin
and 600ft (around 180m) in length. The tape ran at a speedof 9.5cm/s; the four-track, two-channel stereo setup could
record or play back for 32 minutes at a time. However, it wasdifficult to maintain precision in the cartridge itself when it
went into mass production. It required a narrow head gap toachieve the desired level of recording/playback performance,
which was impossible to achieve with the manufacturing andcomponents technology available at the time. This made itdifficult to ensure product quality. Manufacturers were notwilling to come on board and the attempt ended in failure.

Fig. 6.1. RCA cartridge (1)120 x 184 x 12 mm

6.3

Car Stereos and the Endless Cartridge

As audio equipment became more popular for home use in
the United States, it spurred a demand for the developmentof in-vehicle audio equipment, or the car stereo. In-vehicle
entertainment started out with car radios and rapidly gained
momentum in response to user demand, with innovations
such as car audio equipment using disc records (Fig. 6.2).
Development also began on cartridge-style tape recorders
intended for car audio. Vibration is a major issue in vehicles
and disc players were never very popular in cars, as this wasa very difficult problem to overcome. However, vibration
resistance is one of the strengths of tape recorders, making
this issue relatively easily to overcome. As well as needing
to be smaller than the existing models, tape recorders forcar stereos could only be cartridge-type machines, to ensure
operability and to store the tape safely.
The Fidelipac cartridge went on sale in the United Statesin 1962 and became very popular for in-vehicle use. These
cartridges measured 102x133x24mm and held a 6.3mm tapein an endless loop. With a four-track stereo system (twostereo programmes) and a tape speed of 9.5cm/s, these tapes
could play for ten minutes (Fig. 6.3).
In 1965, US company Learjet put out an eight-track
cartridge that was around the same size as the Fidelipac(102x136x22mm) (Figs. 6.4, 6.5). The tape width and speed
were also the same as the Fidelipac, but with eight tracks (fourstereo programmes) it could play for around 60 minutes. The

Historical Development of Magnetic Recording and Tape Recorder215

eight-track was a success and it soon beat all competition
to become the standard car stereo. In a short space of time,it had spread throughout the United States. The early car
stereos in Japan also used the eight-track cartridges. These
cartridges became the popular choice of car stereo tape,
becoming the forerunner of later developments in the CD/
laser disc karaoke machine.

Fig. 6.5. Structural diagram of an eight-track cartridge (5)Fig. 6.2. In-vehicle record player (XLP Record) (2)

Fig. 6.3. Fidelipac cartridge (1962) (3)102 x 133 x 24 mm four-track/two channel

Fig. 6.4. Learjet eight-track cartridge (1965) (4)102 x 136 x 22mm eight-track/two-channel216

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6.4

Emergence of the Compact Cassette

As the car stereo was growing in popularity and the endlessloop cartridge tape was emerging onto the scene in the
United States, a twin-hub cartridge tape was attracting
attention in Europe: the “Compact Cassette” developed by
the Dutch company, Philips. While RCA, mentioned in
Section 6.2, had planned to release its own cartridge design
to European tape recorder manufacturers in the hope that it
would be popularised in Europe as well, no manufacturers
were willing to take it on and the RCA cartridge ended in
failure. While the company later worked with European
manufacturers to make the cartridge better and smaller,
resulting in a new style of cartridge, there was disagreement
among the companies, which ended in a struggle forsupremacy between the following two types of cartridge (Fig.
6.6).
(1) D
 C (Double Cassette) International Type
Promoted by: G rundig, Telefunken, Blaupunkt (allGerman companies)
Released: 1963
(2) C ompact Cassette Type
Promoted by: Philips (the Netherlands)
Released: 1962 test sale, 1964 full sale
Both cartridge types were smaller than the RCA cartridge,
while the tape width, tape speed and other characteristics
were based on a completely new, easy-to-use format
completely unrelated to the open reel specifications. The
Compact Cassette format eventually won out for the reasons
below, although a major reason was Philips’ decision to makeits patent freely available in order to popularise it.
Success factors for the Compact Cassette format:(1)	Smaller cartridge size(2)	Twin hub structure prevented tape jamming andimproved tape running(3)	(The potential for) superior sound quality /performance(4)	Careful development approach of provisional sales
and getting feedback from the market(5)	Free patent licencestrict standards in place and incorporating all kinds ofinnovations within the scope of these standards to produce
a superior product not only gave users greater convenienceand greater confidence in the product and format, but also
prevented innovative technology from being short-lived
in the marketplace. This was the perfect way for Japanesemanufacturers to demonstrate their talents.

It seems that Philips did not originally set out to make thepatent freely available, but it eventually switched to its
free-patent policy while competing with the opposing DC
International format. Around 1963, Grundig proposed toSony that they jointly promote the DC International format;
soon afterwards, Philips made the same proposal regarding
the Compact Cassette format. Philips also approached otherJapanese companies in regard to adopting the Compact
Cassette format, proposing a royalty fee of ¥25 per piece.
When Sony seemed inclined to decline, Philips pressed fora contract at a drastically reduced price. Sony flatly refusedand Philips finally announced it would offer the licence toSony for free. Then, in the light of antitrust laws and its
business credibility, Philips made the bold move in 1965of making the basic patent available to all manufacturers
worldwide rather than just to Sony. One of the conditionsof this was that manufacturers should “strictly adhere to thestandards and strictly maintain compatibility”. This served asa huge boost to the spread and development of the Compact
Cassette.
The Compact Cassette format was strongly focused oncompatibility. Unlike the open-reel system, it was compatible
with mono and stereo (Fig. 6.7). The system of putting

Fig. 6.6. (1) DC International and (2) Compact Cassette (6)Historical Development of Magnetic Recording and Tape Recorder217

Recording/playback Erasing headhead(a) Mono(b) Stereo

Fig. 6.7. Compact Cassette track arrangement (7)6.5

Te c h n o l o g i c a l D e ve l o p m e n t s fo r t h eCompact Cassette

The Compact Cassette started out as a monophonic notetaking machine with none of the so-called Hi-Fi capabilities
for music playing. When Philips brought it onto the market,
the company first made a cautious test sale. While this was
definitely successful in terms of laying the foundation for theCompact Cassette system, a few key technologies needed
to be developed before it could achieve Hi-Fi capabilities
with a slow tape speed of 4.76cm/s and a narrow track widthof 0.6mm (one stereo track) and become a mainstream taperecorder for music use. For the tape recorder to produce
a sound that was closer to the original, it needed a wide
frequency response and a guaranteed dynamic range. This
became the target of technological development. In termsof the mechanical performance of the running of the tape,it was also very important to have a steady tape speed
and to ensure the head stayed in constant contact with thetape without disturbing it. Open-reel machines achieved
better performance by increasing the tape speed andbroadening the track width. Relatively free from structuraldesign constraints, it was also easy to improve the running
performance of the tape on these systems. Although there
were some disadvantages with the open-reel machines, suchas their bulkiness and high tape consumption, they were
the best option in terms of consistent sound quality. Since
the Compact Cassette used far less tape than the openreel systems, as shown in Table 6.1, and had to adhere tocertain standards, there could be no change in tape speed or
track width. Consequently, to improve its basic recording
performance, improvements had to be made to the magnetic
substance on the tape and to the head that played the tape.
It was also difficult to ensure the accuracy of the tapeoperation, since the tape system was contained within theconfines of the cartridge and the mechanism itself was tiny.
Consequently, another major challenge was to develop andimprove the precision of the motor and parts. The major
technology challenges within these various constraints are
given below on a priority basis.

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- Tape: Developing a high-quality magnetic substance better
than ferric oxide- Heads: Developing a core material to make the best useof the magnetic substance in the tape; achieving a stable,
narrow gap- Noise reduction: Developing and (de facto) standardising asystem with high cost performance- Servo technology: Achieving precise rotation control with asmall-scale DC motor / low-speed rotating motor- Improved mechanical precision: Ensuring intensity andaccuracy with small-scale parts; progressively introducing
new materials
Table 6.1. B asic Parameter Comparison of the Open-Reel
System and the Compact CassetteTape Speed(cm/s)
Open Reel

9.5 – 38.0

Compact Cassette

4.76

6.6

Track Width (mm)1.0 (four stereo tracks)
2.0 (two stereo tracks)
0.6 (stereo)

Success as an International
Standard

Tape recorders had their beginnings after the war in the formof open-reel machines. As well as having good sound quality
and long-playing capabilities, these were easier to use thanthe disc-style recorders and soon gained popularity as therecorder of choice. As they reduced in price, they became
popular audio equipment for home use, with music tapes
also becoming available on the market. However, the openreel machines were bulky and somewhat cumbersome touse, which prevented their popularity from spreading evenfurther. As discussed in the previous section, a numberof ideas were put forward in the 1960s to encase the tapein a cartridge. This is when the Compact Cassette hit themarket as the more orthodox of these cartridges. Althoughat first it fought with other formats for dominance, themomentous decision by Philips to licence its patent free ofcharge to manufacturers worldwide succeeded in making it
the de facto international standard very early on. Unifying
the format meant that not only endorsed manufacturers
but also members of the surrounding industries, such as
materials manufacturers and parts manufacturers, could also
confidently make development investments into the Compact
Cassette format, thereby creating a virtuous cycle of rapid
technological enhancement. While the basic small size
specifications meant a lower quality product than the openreel system, the developers focused on improving the limited
recording and playback performance by making various
essential technological developments with the tape recorder,such as working on the tape, heads, noise reduction and servo
control. By the early 1970s, the cassette deck was a fullyrecognised piece of audio equipment. Cassette deck taperecorders had come to be acknowledged as proper magnetic
recording machines and not just toys.

6.7

C o m p a c t C a s s e t t e Ta p e R e c o r d e r s
in Japan

The Philips EL-3301 cassette recorder was first released inJapan in May 1965, ushering in Japan’s Compact Cassetteera. The first sales were not made by electronics stores, butrather by the department store chain Mitsukoshi. At ¥27,000,
they were quite highly priced, but they seem to have sold out
immediately thanks to ingenious PR and choice-goods sales
floor management by Mitsukoshi, which at the time had areputation for sophistication (Fig. 6.8). The following year
in April 1966, Matsushita Electric launched the EL-3301T(Fig. 6.9) with Philips as the OEM; in June that year, Aiwa
released the first domestically-produced model. By the endof the year, Sony, Sanyo, Columbia, Standard and a numberof other companies had launched similar products. By 1967,
fierce development and marketing competition had begun,
with almost all of the major Japanese audio equipment
manufacturers having a Compact Cassette product line-up.

Fig. 6.9. Matsushita EL-3301T (1966) (9)6.8

S t a n d a r d i s e d C a s s e t t e Ta p e
Recorders

By the time the Compact Cassette appeared, tape recorders
had a diverse range of applications, such as learning tools
for studying. Although there had been a lot of competition
to develop a high quality tape deck for recording music,
everyday tape recorders for home use were battery operated,monophonic devices and, to a certain extent, fairly low
priced. While the 3-5” open-reel tape recorders for home use
had been fairly well-received on the market, they were big,heavy and difficult to use; the users had to know how to work
the machine and mainly tended to be young people such as
students. The appearance of the Compact Cassette presented
an opportunity to expand the target consumer group to
include those who had previously not been considered, suchas women and the elderly. This provided a huge boost to thetape recorder market for home use. With the range of target
users expanding to include a wider range of ordinary people,
the external appearance of the tape recorder inevitably
underwent some design changes to make it more appealing;
an increasing number of Compact Cassette machines wereflat in shape with built-in microphones and piano-key
button operation (Figs. 6.10, 6.11). Stereophonic machinesthat doubled as tape decks appeared in the product lineups
alongside the general monophonic machines. Compact
Cassette machines were becoming the mainstream taperecorders of choice.

Fig. 6.8. Philips EL-3301 catalogue at the time the productwas launched (1965) (8)Historical Development of Magnetic Recording and Tape Recorder219

Fig. 6.10. Sony TC-100 (1966) (10)Sony’s first Compact Cassette machine

Fig. 6.11. Sony TC-1160 (1968) (11)The first machine with an inbuilt electorate

capabilities. Since these devices were intended more for DC
operation, battery lifespan was also a major issue. Reducing
energy consumption was the prime focus for this category of
product.
The concept embodied in the TC-50 continued in its
successors. It was followed by the TC-1000 (1972), which
had various improvements in function and performance, suchas an anti-rolling mechanism and auto-shutoff feature, as wellas improved operability through its button-type operation. By
1978, the series had developed as far as the TCM-100 (Fig.
6.13), which, complete with a coreless motor, became themother of the first “Walkman”.

Fig. 6.12. Sony TC-50 (1968) (12)condenser microphone

6.9

Ultra-Small Handheld Devices

Sony brought out its first Compact Cassette tape recorder,
the TC-100, in 1966. Operated by AC mains, battery or car
cigarette lighter, its cassette pop-up mechanism, piano key
buttons and other features made it easy to use in terms offunction. It was quite deep and rectangular in shape, closely
resembling the early Philips machines, and was usually onlyused on a desk. To fully play on the strengths of the Compact
Cassette, tape recorders had to be user friendly, with onehand operation and an input microphone. Of course, theyalso had to be small, lightweight and battery-operated. In
1968, Sony released the TC-50 (Fig. 6.12), featuring an
inbuilt microphone for dictation, one-hand operation and an
original shape. This model could be seen as an attempt at
downsizing the Compact Cassette player. The operability andmobility afforded by the inbuilt microphone was well-noted;
the machine received much attention thanks to its use by thecrew aboard the Apollo 10 spaceship (Fig. 6.14). Since themain target markets for this type of small-scale tape recorderwere business use, such as for data collection and dictation,and educational use, such as for conversation drills andlessons, it was more important to make the machine smaller,
lighter and more operationally reliable than to give it Hi-Fi

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Fig. 6.13. TCM-100 (1978) (13)“Pressman”

Fig. 6.14. The TC-50 aboard the Apollo

6.10“K appa” B ook Sized Tape
RecordersUltra-small, handheld tape recorders such as the TC-50
were often used in business for tasks such as data collection.
Proposals were made to design standard home-use taperecorders in such a way as to make them useful for businesspurposes as well. Developers began focusing on downsizing
and especially slimming down these machines, so that as well
as being functional, they could be used on a desk or put in abriefcase. A slimmed down tape recorder was the engineer’s
dream. Rapid improvements in technology among parts
manufacturers in the early 1970s meant higher-precisionparts, enabling the design of mechanisms that were thinnerthan had previously been possible. In 1975, Sony released theground-breakingly slim TC-1100 (Fig. 6.15), only 29.5mm
in thickness. Not only was this model slim, it also had asurface area comparable to that of a “Kappa” book, a wellknown style of paperback with a defined size of 11 x 17cm.
With this very smart, impressive design, it was a success,with endorsements ranging from business use to home use.
The single Compact Cassette tape recorder can be said tohave developed from the TC-50 into the handheld headphone
stereo, reaching its final form in the slim models such as the
TC-1100. For a long time, the TC-1100 series dominatedthe general tape recorder market for business and homeuse, bringing out similarly-sized multifunctional devices
that incorporated radios, as well as other follow-on models
with better designs. Fig. 6.16 shows the mechanism of theTCM-280, one such follow-on model. The design makes
much use of stainless steel in various parts such as levers,
allowing thinness as well as strength. The slim, brushed DC
servomotor uses counter-EMF. The permanent magnet DC
erase head reduces electric current consumption, while thestandard-sized recording/playback head is of permalloy (Fig.
6.17).

Fig. 6.15. Sony TC-1100 (1975) (14)The first Kappa book sized device

Fig. 6.16. TCM-280 mechanism

Fig. 6.17. TCM-280 erase head, recording/playback head

6.11

Cassette Densuke and the Live
Recording BoomIn 1973, eight years after the Compact Cassette appearedin Japan, Sony released the portable TC-2850SD (Fig.
5.12), a Hi-Fi deck. Even though this model was batteryoperated and portable, it had all the capabilities of a proper
tape recorder, equipped with a high-grade microphone
amplifier, a Dolby noise reduction system and a high-quality
recording amplifier. Since its functionality and performance
were outstanding for a portable Compact Cassette player,
it came to be known as the “Cassette Densuke”, inheriting
the pet name that had been used for portable, business-use
tape recorders. The introduction of this model triggered a“live recording boom”, with a slogan describing it as “noordinary deck mechanism”. It also played a major part inboosting the confidence of general and business users in thesound quality and potential of the Compact Cassette. Even
though the TC-2850SD was a high-performance model, its
mechanism was the standard format of the day; the focus
had been on higher quality recording and stable performance
rather than downsizing it and including an amplifier unit.
With the success of this model, a number of other similar
high-performance, portable Compact Cassette recorders were
produced. Five years later in 1978, Sony released the TC-D5(Fig. 6.18), combining both small size and high performance.
While the “live recording boom” had died away, the TC-

Historical Development of Magnetic Recording and Tape Recorder221

D5’s small, sharp-looking design and outstanding basic
performance were highly regarded. The model became along seller, being well received by users serious about soundquality, from high-end amateurs to professionals. However,small-scale, portable tape recorders had one weakness: therotational accuracy of the capstan, which was the pivotal
part of the tape drive. To improve this accuracy and also toprevent the rotation being disturbed by external interference,
the TC-D5 incorporated a “disc-drive” driving system. The
basic configuration of this system was a small coreless motor
in direct contact with a rim-driven flywheel on the capstan
spindle, with a frequency generator fitted onto the flywheel
to detect rotation. Ingenious details such as the materials
used and the contact pressure on the motor pulley and the
flywheel allowed the driving force to be transmitted cleanly
while preventing the motor from vibrating (Fig. 6.19).

constrained standards, revising and improving the tape heads
and the drive system, including the mechanisms and the
motor. The resulting superior cassette decks hit the markets
as fully recognised items of audio equipment. The Japaneseaudio equipment industry steadily gained confidence throughcompetitive development and eventually decided to set new,Japan-specific industry standards.

(1) Micro-Cassette
The Micro-Cassette is a tape recorder that uses smallscale cartridges around one quarter the size of the Compact
Cassette. The tape width was 3.81mm, the same as theCompact Cassette, while the available tape speeds were
2.4cm/s and 1.2cm/s. With standards set by Olympus, it
was put on the market in 1969 as the Pearlcorder. In 1974,
Olympus, Sony and Matsushita set their own standards
together and each company released a small-scale memo
recorder. While it gained some popularity due to its small
size, it never reached as extensive a range of uses as theCompact Cassette.

(2) Elcaset

Fig. 6.18. Sony TC-D5 (¥99,800) (1978) (15)Coreless motor
Disc-drive type
capstan servo

The Elcaset was a tape recorder standard jointly developed
and announced in 1976 by Sony, Matsushita and TEAC
that combined the sound quality of the open reel with theease of use of the Compact Cassette. The tape width was
6.3mm, the same as the open-reel machines, and the tapespeed was 9.5cm/s. The tape came out in A6-sized cartridges.
Although products were developed and marketed by thethree companies, they were not widely popular and soon
disappeared from the market.
While both of the above new Japanese standards sought toperfect aspects lacking in the Compact Cassette, they were
not widely popular. They were neither very marketable norvery necessary, since they served only to supplement what
the Compact Cassette lacked. Compact Cassette machines
had had a head start in development; they were also being
produced in large quantities and therefore at lower cost.
However, Japan’s achievements in developing international
standards proved to be an invaluable experience when Japan
later led the world into the digital era.

Fig. 6.19. Perspective drawing of the TC-D5 drive system (16)References1) 	50 Years of Audio. Japan Audio Society Publishing,

6.12

December 1986, p. 483.

Other Cartridge Tape Recorders

While the early Compact Cassettes lacked the capability formusic recording, Japanese audio equipment manufacturers
worked hard on improving performance within the tightly

222

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 20122) 	Mori, Yoshihisa, et. al. Onkyō-Gijutsu-Shi [History ofSound Recording], Tokyo University of the Arts Press,
March 2011, p. 57.
3) 	50 Years of Audio, p. 498.
4) 	Ibid., p. 499.

5)Onkyō-Gijutsu-Shi, p. 88.

9)Provided by Panasonic Corporation.

6)

Ibid., p. 89.

10), 11), 12), 13), 14), 15), 16) Provided by Sony

7)

50 Years of Audio, p. 500.

8)Ibid., p. 503.

Corporation.

Historical Development of Magnetic Recording and Tape Recorder223

7 Structure and Performance of Compact Cassette-Type Tape Recorders
7.1

the freer open-reel era was carried over into the Compact
Cassette as well. Fig. 7.1 shows the various Compact
Cassette tape recorder formats.

Ty p e s o f C a s s e t t e Ta p e R e c o r d e r s
According to Head Arrangement

Although Compact Cassette machines started out as socalled memo recorders and were initially limited in termsof function and performance, as the competition forstandardisation ended and the Compact Cassette became
recognised as the standard format, development rapidly
began on increasing its functionality and performance. The
original construction was in cartridge form and presumed a
two-head configuration only: an erase head and a recording/playback head. Various head formations were devised, but
in the end the head formation that had been put to use in

7.2

Fig. 7.2 shows the basic structure of a tape recorder.
The input signal passes through the equaliser after being
adequately amplified; it is then applied to the recording headwith the bias signal added to it. The tape moves in frontof the head (Fig. 7.3) at a fixed speed and is magnetised inproportion to the strength of the magnetic field coming fromthe gap in the recording head, thus recording is achieved.

Erase head

Playback head(a) 1 way playback

Erase head

Small-window Recording/playbackerase head
combination head(d) 3 head, 1 way closed loop dual capstan

4 ch head
Erase/recording/playback combination head(e) rotary head reverse

Recording/playbackhead(b) 2 head, 1 way

Recording/playback
combination head(c) 3 head, 1 way open reel

Basic Structure(f) 4 ch head reverse (dedicated playback)Fig. 7.1. Compact Cassette tape recorder formats and head arrangement (1)224

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

Input current
Input

Recordingequaliser

AmplifierPlaybackequaliser

AmplifierOutputRecording head winding current

Bias current
Biasoscillator
Erase current

Erase Recording Playback
head
head
head

Tape

Fig. 7.2. Basic structure diagram of a tape recorder (2)

Coil
Core
(iron core)

Head gap

Fig. 7.3. Diagram of the magnetic head principle (3)7.3

Recording mechanism

The magnetisation curve of tape is represented by what iscalled a hysteresis curve rather than a straight line. As acurrent passes through the head coil, the magnetisation of
the tape that is in contact with the gap alters in a hysteresis
loop pattern in response to variations in the magnetic field
H. As the tape moves, the magnetic field applied to thatparticular point on the tape returns to 0 once it has gone past
the gap. If the applied AC current (recording signal) has ahigh frequency, the magnetic field is reversed and returns to
0. Consequently, while residual magnetisation is achievedin a small loop, the recorded magnetisation waveform isgreatly distorted because the initial magnetisation curve is
non-linear. Accordingly, a sine wave is passed through therecording head at a higher frequency than the recording
current as a means to avoid this distortion. This is called ACbias recording and is an indispensable piece of technology
for ensuring good electromagnetic conversion in analogue
recording (see Fig. 3.6).

7.4

Loss during Recording

Loss (signal attenuation) at the recording head tends tobe greater the higher the frequency, as shown in Fig.
7.4. Self-demagnetisation loss is the mutual negation of
adjacent magnetic flux as the recorded wavelength on thetape decreases. Recording demagnetisation loss increases
the higher the frequency; like AC bias, at very highfrequencies the minor loop converges at 0 and nothing isrecorded. Penetration loss is loss caused by differences inmagnetisation between the surface of the tape and the deeper
levels of magnetic particles on the tape due to different
depths of magnetisation on the tape. Core loss is loss causedby eddy currents in the head core. Recording spacing loss
is loss caused by a space forming between the tape and thehead gap; however, this has less effect during recording thanduring playback.

Relative levels of tape magnetisation (dB)

When the recorded portion of the tape is rewound and passedby the playback head at the same speed, the magnetic flux
on the tape passes through the gap to the head, inducing acurrent corresponding to the magnetisation on the tape when
the tape was wound. Playback is achieved by this signal
being output through the playback amplifier.

(1) Self demagnetisation loss
(2) Recording demagnetisation loss
(3) Penetration loss
(4) Core loss(5) Recording spacing loss

Recording current frequency (Hz)Fig. 7.4. Loss during Recording (4)7.5

Loss during Playback

Ideally, a playback head should increase in output inproportion to frequency. In reality, however, various losses
occur when a tape is played back (Fig. 7.5). Gap loss is loss

Historical Development of Magnetic Recording and Tape Recorder225

tape type. Equalising low frequencies meant increased noisewith any rise in gain, so the low frequency time constant was
flattened (Fig. 7.6).

IEC Type NumberTime Constant (μs)
T1
T2

I (normal tape)120

Folding Frequency (Hz)
f1

f2
1326

II (chrome tape)
III (ferrichrome tape)

3180

70

50

2274

IV (metal tape)

Response (dB)caused by gap width: if the recorded wavelength is equal
to the gap width, there is no output. Playback spacing loss
is loss due to a space forming between the tape and the gap
in the playback head. This can be caused by the surface
properties of the tape, the tape driving performance, thetape tension or other factors. Azimuth loss is caused bya misalignment between the playback head gap and theazimuth angle of the recorded signal (determined by the
relative position of the recording head gap and the tape).
Spacing loss and azimuth loss are largely due to tolerancesof the core mechanisms of the tape recorder, including thetape drive system. Particular attention needs to be paid tothis when designing mechanisms. Since there are limited
options for head arrangement on Compact Cassette machines
in particular, it is very difficult to improve azimuth precision
on reverse machines and three-head machines. Headarrangements with no pads inside the cassette (such as heads
that are inserted through a small window) cannot ensure
proper contact between the tape and the head and are thus
susceptible to spacing loss. Thickness loss is loss related tothe effective depth of magnetisation during playback.

Frequency (Hz)Fig. 7.6. Compact Cassette playback equaliser (6)References1) 	Saishin Ōdio Gijutsu [Latest Audio Technology],

Induced voltage in head coil (relative value) (dB)Ohmsha, April 1991, p. 158.

(1) Gap loss
(2) Playback spacing loss
(3) Core loss
(4) Azimuth loss
(5) Thickness loss

Where
g: gap width
λ: recording wavelength
w: track width
θ: tilt angle (radians)

Frequency (Hz)Fig. 7.5. Losses during playback (5)7.6Playback Equaliser

A characteristic of magnetic recording is that although
the output of the playback head is relative to the speedof variation in magnetic flux, certain losses are evident
at high frequencies. Consequently, a balanced frequency
response can be achieved in a tape recorder throughplayback compensation (equalising) that separates the mid
and low frequencies, where loss is negligible, from the highfrequencies, where loss is not negligible. This had to be
standardised relatively early on, because there would be littlecompatibility between machines if every different device
were to make this compensation in a different way. Compact
Cassette machines had different playback equalisers for each226

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 20122)

Ibid., p. 146.

3)

Ibid., p. 146.

4)

Ibid., p. 150.

5)Ibid., p. 151.

6)

Ibid., p. 153.

8 Magnetic Tape in Compact Cassettes
8.1

Development of Magnetic
Substances

Development of ferric oxide magnetic tape continued withthe basic aim of trying to improve its recording performance.
Unlike the open-reel system, the Compact Cassette taperecorder system meant very little freedom in terms of tapewidth, tape speed and head formation. Since compatibility
had to be strictly adhered to, there was a strong demand to
improve the performance of the magnetic tape itself. The
early Compact Cassette tapes were lacking in performancein terms of music recording. Development of magnetic
substances quickly got under way in order to make thissystem into an all-purpose tape recorder for recording
everything from conversations to music.

Evaporated

CoatedAlloy powder
CrO2
Co containing γFe2O3
γ•Fe2O3 (Fe3O4) (high coercivity)γ•Fe2O3 (micro particles)γ•Fe2O3 (standard size)

Fig. 8.1. Estimated developmentof magnetic substances on tape (1)Fig. 8.1 is a chart proposed in the 1970s showing theestimated development of magnetic substances on tape.
First, attempts were made to physically improve the tapeand magnetic substance by developing and improving themagnetic ferric oxide powder, increasing the packing ratio
by making the particles smaller and improving the tape’s
adherence to the head by making the tape surface smoother.
At the same time, improvements were being made to theprocess of applying the magnetic powder to the tape, as
well as to the adhesives and additives, the so-called binders,that went into the magnetic powder. Work was also being
done to improve the mechanical precision of the tape by
improving the tape cutting machines (slitters) and otherelements in the manufacturing process, enabling the creationof a more delicate and higher-precision tape than open-reeltape. However, the most important tasks were to downsize
the product and improve its ease of use. Developers hadvery constrained conditions under which to achieve proper

recording performance, so they had to focus on developing
and improving the magnetic substance itself to improve tapeperformance. The Compact Cassette philosophy of strictly
maintaining compatibility not only spurred on productdevelopment, providing users with small, lightweight taperecorders that were easy to use, but also forced developers
to improve the performance of the technology under very
restrictive conditions. This was the driving force that madethe development of the Compact Cassette so definitive.

8.2

Development of Chrome Tape

In 1970, BASF released a “chrome tape” that used chromium
dioxide as the magnetic substance. This tape was a major
improvement in terms of a high-frequency response that
could not be achieved with ferric oxide tape. Up until thistime, all Compact Cassette players had a playback equaliser
time constant of 120μs; the arrival of the chrome tapemeant a time constant of 70μs could be used. This became
the standard value for high frequency compensation for
high-performance tape. Once BASF developed its chrometape, Japanese manufacturers also came up with their own
chromium dioxide tape. In 1973, Sony released its “DUAD
tape”, double-coated with ferric oxide and chrome. The ferricoxide layer on this tape compensated for the lack of energy(or lack of sensitivity) in the mid and low frequency rangethat was a shortcoming in chrome tape. In turn, the highfrequency response of chrome made this a high performancetape. Although this type of tape became standardised as theType-III, it was not highly popular and went out of use in
the 1980s. Although double-coated tape had a reputation
for good sound quality and had also been used in openreel systems, it faced pressure from the high performanceand price competitiveness of Type-II tapes such as cobalt
tape. When metal tapes appeared, it lost much of its purposeand exclusive Type-III products faded from the market.
While chrome tape was ground-breaking in terms of highfrequency response and played a huge part in improving theperformance of Compact Cassettes, it gradually disappeared
off the market in Japan due to patent licencing issues andpollution issues with hexavalent chromium effluent fromcoating factories. Instead, cobalt-deposited ferric oxide(CoFe2O4, crystal growth of cobalt ferrite on the surface offerric oxide) tape with similar properties became the main
high-performance music tape in use. Eventually, most of theType-II tape was this so-called “cobalt tape”.

Historical Development of Magnetic Recording and Tape Recorder

227

8.3

With stereo records becoming popular and FM broadcasts
reaching full swing in the late 1960s, the audio market
flourished. The Japanese audio industry entered a phase of
furious development in exports. While Compact Cassettemachines were a mainstay of this trend, as the audio
market expanded, there was increasing demand for further
performance improvements in the Compact Cassette. The
magnetic properties of the tape had to be improved, but thestandards had to be strictly maintained. The race was on to
get a new, high-performance magnetic substance out of thelaboratory and onto shop shelves. Developers first came up
with chromium oxide; the next development was cobalt.
Finally, they came up with metal tape (metal powder tape)and set about putting it to practical use. Nagai, Iwasaki, etal. had already reported some research results at Tohoku
University regarding tape for short wave recording around1963. Although this was recognised to have better qualities
in theory, there was no obvious need for the product andno incentive to solve the various difficulties faced in
manufacturing it. High-performance Compact Cassettes
presented such a need, and metal tape, originally considered
to be for video use, was put to practical use.
Despite being called metal tape, it was actually a type ofcoated tape very similar in composition to the existing ferricoxide tape rather than a completely new composition, suchas the evaporated tape discussed in a later section. The
difference was that the magnetic substance used was metal
particles (iron). This meant a superior magnetic substancecompared to ferric oxide because the lack of oxygen atoms
increased the density of the metal, thereby adding to themagnetism of the substance; however, it was also very
susceptible to oxidation. It was important to develop antioxidation or rust-proofing measures to be incorporated into
the tape manufacturing process, as well as a method for
producing metal particles. A number of companies tried tosolve this issue through various means, such as coming up
with different binder materials or putting anti-rust properties
into the magnetic particles themselves. A major argument
was the lack of compatibility: the tape was highly retentive,
and could not be recorded onto or erased using existingmachines. However, such concerns were far outweighed by
the desire for better sound quality, and a new standard, theType-IV, was established. The final stage in the evolution of
the Compact Cassette had taken place. The development ofmetal tape not only proved useful for audio, but also madea major contribution to the improvement, downsizing anddigitalisation of small-scale video tape recorders and thedevelopment of audio and video equipment.

228

8.4

Appearance of Metal Tape

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

Creation of Practical Evaporated
Tape

During the same period of time, Matsushita achieved anotherdream: thin metal film tape. Although thin metal film tape
was considered ideal, as it does not require a binder like
coated tape does, it required a new manufacturing techniqueto achieve such a product in tape form. Matsushita developed
the evaporation coating method, in which an evaporated
coating could be continuously formed on a base product (Fig.
8.2). It was originally developed as a means of evaporation
coating for the production of film capacitor electrodes.
While evaporated tape offered superior magnetic properties,
it also had several flaws when used in tape recorders. It
adhered to the head very well, as the surface of the tape
was far smoother than coated tape; however, it could cause
too much friction against the head and the tape guide, so
an appropriate lubricant was required. The magnetic layer
was very thin, so care had to be taken to ensure it did not
deteriorate, even when highly durable materials such as
nickel or cobalt were used for the magnetic film. Thesevarious hurdles were cleared and the first evaporated tape –“Ångrom” tape – was created for the microcassette in 1978.
In 1984, an Ångrom Compact Cassette went on sale as aType-II tape. This evaporated tape was later developed foruse in video, just as the metal tape was, and full use wasmade of its high density recording properties. It became avery important tape in the era of audio/video digitisation.

Fig. 8.2. Example evaporation-coating device (2)References
1)

Jiki Kiroku Gijutsu Dai 3-Kan [Magnetic Recording
Technology Volume 3], Japan Industry Engineering
Center, May 1980, p. 87.

2)

Jiki Kiroku Gijutsu Dai 3-Kan [Magnetic Recording
Technology Volume 3], Japan Industry Engineering
Center, May 1980, p. 89.

9 Advances in Magnetic Heads for Compact Cassettes
9.1

Recording/Playback Head Structure

Magnetic heads used in tape recorders comprise a magnetic
circuit of a coil wrapped around an iron core with a partcut away. Magnetic recording occurs when a magnetic
field is applied to the tape through this cut-away section,or gap. For playback, the magnetic flux on the tape passes
through the gap, inducing a current in the coil, which isthen amplified (see Fig. 9.1). The core material must be
sensitive to microscopic changes in magnetism. Since highmagnetic permeability is needed to increase the effectivenessof the magnetic circuit during recording, many of the early
heads were made of permalloy, an alloy of nickel and ironwith high magnetic permeability. The magnetic head is awound coil with impedance that increases in proportion tofrequency. As a result, the higher the frequency, the greater
the “core loss”, loss caused by eddy currents. To reduce thiscore loss, a laminate structure is used, made up of several
layered sheets of permalloy (Fig. 9.2). The head is also
designed so that the magnetic circuit is narrower near thegap, so as to increase the effectiveness of the exchange ofmagnetic flux. The front part of the head that comes into
contact with the tape is called the tape contact surface. Since
it is in constant contact with the tape, it is very important for
it to be abrasion-resistant; it must have very smooth frictional
properties so as not to adversely affect the running of thetape. In actual heads, the contact surface comprises a shield
between tracks (if there are multiple track heads, such as forstereo), a dummy segment without tracks and a resin material
to hold these in place. If these different materials do not wear
evenly, this affects the contact with the tape and may resultin spacing loss. Accordingly, every head-manufacturing
company has come up with its own ideas on which materials
to select and how to polish the contact surface.

Core
Coil
Head gap
Laminate core
Resin orsimilarShield case
Shield between
channels

Fig. 9.1. Typical magnetic head structure (1)

Coil

Case

Terminal

Dummy

Mounting plate

Gap

ShieldCore(Inside of the case
encapsulated in resin)

Fig. 9.2. Laminated head structure (2)9.2Types of Heads and theirCharacteristics(1) Recording Heads
The aim of these heads is to generate a large and effective
magnetic field with very little current and magnetise thetape precisely and accurately. They are configured to havea slightly larger gap of around 3-5μm to avoid magnetic
saturation at the gap and increase the effectiveness of therecording penetrated into the tape. Impedance is set to 10Ω at
1kHz for an electrical circuit providing a bias current(2) Playback Heads
The priority for these heads is to reduce gap loss in order toplay back at as high a frequency as possible. Accordingly,
they have a far narrower gap than recording heads, at around
1.0μm. Since they have an increased number of winds in

Historical Development of Magnetic Recording and Tape Recorder229

the coil to make the playback output as high as possible(increased sensitivity), they automatically have a highimpedance of 1kΩ at 1kHz. As well as being highly sensitive,
playback heads are connected to a playback amplifier,so require strong magnetic shielding to prevent external
magnetic induction and noise generation.

(3) Recording/Playback Combination Heads
The basic two-head type Compact Cassette tape recorders
use the same head for recording and playback in order tomake the device simpler and keep the price down. Many ofthese recording/playback heads have a gap of 1.3-1.6μm in
consideration of magnetic saturation during recording as well
as gap loss during playback. Since the parameters of theseheads are not optimum for either recording or playback, they
are inferior in performance to the three-head type, which uses
individual recording and playback heads. However, for as
long as Compact Cassettes used ferric oxide, they achieved
adequate high-end performance.

Fig. 9.3. Four-gap ferrite erase head (3)(4) Erase Heads
Many AC erase heads use ferrite materials, which generatestrong magnetic fields with little heat generated from eddy
currents. But with the appearance of metal tape, erase heads
needed to generate even stronger magnetic fields. AlthoughSendust erase heads were developed that could achieve this,they were extremely cost-prohibitive, so other alternatives
were devised, such as improving the ferrite material andincreasing the number of gaps (Fig. 9.3). Low-cost, popularmodel machines were not really capable of playing andrecording on high-performance tape such as metal tape.
Many of them used a DC erase method with erase heads
made from permanent magnets. In such cases, rather thansimply using a magnet, the head surface was magnetised in
an N-S-N-S arrangement to give the effect of AC erasure
as the tape passed by. Combination products such as radio
cassette players often used permanent magnet erase heads to
avoid causing radio interference with a strong magnetic field(Fig. 9.4).

230

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

Fig. 9.4. Permanent magnet erase head (4)9.3

Advances in Materials for Magnetic
Heads

9.3.1 Ferrite Heads
The Compact Cassette started out using ferric oxide tape.
As these tapes became more widely used, it became a major
challenge to solve the quality performance issue resulting
from narrow track width and slow tape speed. In the late1960s, stereo records, which were already firmly established
as a music medium, improved greatly in sound quality due toimprovements in recording and cutting technology, creating
an even greater demand to improve the sound quality of
consumer tape recorders. While development continued
on high-performance open-reel machines such as studiorecorders, this was increasingly heavy-duty equipment foranalogue recording and therefore highly priced. Naturally,
this resulted in a greater demand in the home audio and car
audio markets for a small-scale, affordable machine that
could record and play music on Compact Cassettes. As
discussed in Section 8.2, researchers worked on improving
the magnetic substance on tape, creating chrome tape in1970. This tape was superior in a wide range of applications
and succeeded in expanding the existing recording andplayback bandwidth of 10kHz to around 15kHz, which could
comfortably be called Hi-Fi. In terms of compatibility, a new“Chrome Position” (later Type-II) was defined, with a highfrequency playback time constant changed from 120μs to70μs to match the rise in high-frequency sensitivity. WhileFerrite

Sendust
Per

Ha

y
llo

ma

Amount of wear (μ)

the greater recording and playback performance of chrome
tape played a major part in Compact Cassette machines being
accepted as audio equipment, the surface of the tape washarder than ferric oxide tape and caused problems with wearon the heads. To solve this problem, developers brought out
an abrasion-resistant ferrite head (Fig. 9.5). Since ferrite ismade of compression-moulded powder, it has relatively low
manufacturing costs. It forms a hard core material following
sintering, but this is easy to grind or cut and therefore easy
to achieve dimensional accuracy. As well as being very
hard and resistant to wear, ferrite heads also offer a very
dimensionally stable gap, with glass layers fused between
layers of ground core material. They maintain their initialproperties for a very long time and are extremely stable evenwith changes in temperature and humidity (Fig. 9.6).

rdpe

and amorphous

rm

all

oy

Running time (hours)
Fig. 9.5. Wear properties according to head material (5)Glass-fused gap
Ferrite headFig. 9.6. Ferrite head gap structure (6)Sony had used ferrite heads in open-reel machines from avery early stage. It used ferrite not only for the core material,
but also the entire contact surface of the head, including thedummy segment. This rugged and highly abrasion-resistanthead was called the “F&F Head” (Fig. 9.7) and also became
widely used for Compact Cassettes.

Fig. 9.7. F&F Head (7)9.3.2 Sendust Heads for Metal Tape
Metal tape appeared in 1978 at the onset of the digital audio
era. This tape was the music tape trump card for the Compact
Cassette, able to record and play back sounds that requireda high resolution and a large dynamic range, like computer
music. While it was understood that metal tape had groundbreakingly superior magnetic properties because it used amagnetic substance of metal powder rather than oxide, thiscontravened the Compact Cassette policy of “maintaining
compatibility”.
In short, metal tape used a strongly magnetic substance.
Compared in terms of coercive force (saturation flux density)
Hc and maximum residual magnetisation Br, the values forthe existing chrome (cobalt) music tape were in the vicinityof Hc=600-700Oe, Br=1500G, while the values for metaltape were almost double at Hc=1000Oe, Br=3000G. Hc
represents the high frequency recording level (the quality of
the high-frequency response) as well as the ease of erasing or
the strength of the magnetic field required for magnetisation.
The ferric oxide tape first used in Compact Cassettes had an
Hc of 350-400Oe. While this value was higher for chrometape, the existing heads were still adequate for erasing andrecording. However, to record at full capacity on Hc=1000Oe
metal tape required a stronger magnetic force and a greater
bias current in the head. Since the existing head materials(permalloy or ferrite) had a low saturation flux density, any
increase in current flowing through them would simply
convert to heat rather than provide any effective increasein magnetic flux. Likewise, there was a fatal compatibility
flaw for erasing, as the existing erase heads would not erase
the tape. A discussion commenced on whether or not tochange the high frequency time constant for chrome tapefrom 70μs to 50 or 35μs to make a marked improvement inhigh-frequency response during playback. One opinion said
that the latest technology should be actively incorporated,because fussing over standards and compatibility prevented
technological progress, but this meant that the compatibility
that was such an important factor in the Compact Cassettewould be likely to come undone. However, the latest
improvements in performance were sought after in the musicscene and could not be ignored. The EIAJ (now JEITA)
formulated an international standard in a short space of timewith the help of international organisations such as IEC andHistorical Development of Magnetic Recording and Tape Recorder231

metal tape Compact Cassettes were introduced. The playback
time constant was set at 70μs, the same as for chrome tape.
Although the compatibility policy had been closely adhered
to for playback, such as maintaining playback on existingmachines, a new head (with more efficient materials anddesign to supress heat and prevent saturation even with ahigh bias current) was absolutely necessary for recording.
While ferrite was used in large quantities in highperformance heads due to its superior abrasion-resistanceand the ease and low cost of manufacture and production, it
was unsuitable for metal tape due to its low saturation flux
density of around 5000G. Sendust gained much attention at
this stage (Table 9.1). Sendust is an iron-aluminium-silicon
alloy invented in 1935 by Dr. Hakaru Masumoto and othersat the Tohoku University Institute for Materials Researchand used as a magnetic powder core before ferrite wasdiscovered. Although it has superior magnetic properties
and has cost benefits due to the abundance of raw materials
for it, it has limited uses as it is extremely hard and brittle
as a metal (alloy) and difficult to roll out like permalloy.
Nevertheless, it gained immediate attention with the adventof metal tape. The worst characteristic of Sendust was itsdifficulty in processing. While vacuum-melted Sendust
ingots were cheap, it was expensive to grind and polish themto make heads. Usually, heads had a laminated structure,
made up of ground and polished cores 0.2-0.3mm thick.
This thickness was a compromise to keep processing costs
down; even thinner layers would have been better for highfrequency response. Various attempts were trialled to makea thinner product, such as the method of melting at hightemperatures and then rapidly cooling the alloy in ribbons(ribbon Sendust) or an attempt at rolling the alloy, but it was
not suitable for mass head production due to the difficultyin handling the brittle ribbon. One possible method to curb
high-frequency loss was the composite S&F Head (Figs. 9.8,9.9), with the tip of the head made out of a small block of

Sendust, thus making the gap area highly magnetic, while
the rest, which did not need to be so strongly magnetic, wasmade out of ferrite, which has hardly any high-frequency
loss. The gap area had more or less the same structure as thatof a ferrite head (Fig. 9.10), with the abrasion-resistance of
Sendust rivalling that of ferrite. The product was welcomed
as a highly reliable, long-life device. Sony, Matsushita andother companies made this type of head; these were widelyused in high-performance cassette tape recorders from themetal-tape era onwards.

ShieldNon-magnetic
mask
Hard quartz
glass
SendustMetal core
Ferrite corerow-weldedarea

Fig. 9.8. S&F Head structure (9)R channel coil Shield caseSendust mask

SendustShieldSendust core
Permalloy shield caseFerriteFerriteL channel coilFig. 9.9 S&F Head magnetic circuit (10)Table 9.1. Characteristics of Magnetic Head Core Materials(8)Initial permeability μi

Material

FerritePermalloy

SendustAmorphous

232

1kHz

10kHz

100kHz

Rec/Play 10,500

9,700

8,800

Magnetic Coercive Specificflux density force Hc resistanceBs (gauss)(Oe)(μ-Ω-cm)
4,500

Hardness Density(HV)(g/cm3)Magnetostriction
constant λs (x10-6)

0.03

106

680

5.0

5.0

9

700

4.9

2.0

Erase

3,500

3,300

3,300

5,000

0.14

10

Popular39,00011,700

2,000

7,800

0.012

55

110

Hard

45,00010,000

2,100

6,600

0.013

65

200

HiB

15,000

4,300

930

8,100

0.03

55

150

Popular15,000

3,800

810

8,500

0.007

85

500

1.5
8.7

Core
thickness
(μm)

50
100
100

1.0

150

HiB

11,8003,200

720

10,000

0.025

85

480

6.8

1.0

150

HiB

20,000

9,000

3,000

11,500

0.02

140

850

8.1

0

30

Hiμ

50,00040,000

9,000

8,000

0.012

140

850

7.7

0

30



National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

Glass-fused gap area
Ferrite head

Sendust core
Hard quartz glass

heads took over from Sendust heads, first used in high-end
machines such as three-head decks, then in other devices
competing for high sound quality (Fig. 9.14).
Pressurised gas
for pouring
High speed
rotating cooler

Special metal(a) F&F Head(b) S&F Head

Crucible
Molten alloy
Ultra-rapid cooled
alloy ribbon

Fig. 9.10. Comparative gap areas structures (11)Fig. 9.12. Diagram of the rapid cooling principle (13)Fig. 9.11. S&F recording/playback head (12)Head for metal tape compatible cassette deck

9.3.3 Adoption of Amorphous Alloy Head Material
Although a lot of Sendust was used in heads for metal tape,its saturation flux density was slightly reduced, as otherelements such chrome and molybdenum were being added to
it to increase its durability as an audio head. While successive
studies were made on how to improve it by modifying thetype or amount of additives, it was impossible to achieve asaturation flux density any higher than 10,000G.
Amorphous alloys emerged as a more effective headmaterial that could transcend this limitation. Non-crystalline
amorphous alloys differed in various ways from existing
metals with a crystalline lattice structure. When metals
melt at high temperature, they have a completely randomarrangement of atoms; if they are rapidly cooled, they retain
this property even at normal temperatures, thus forming an
amorphous alloy. The cooling rate to achieve this is around
10,000-1,000,000ºC/s. In practice, amorphous alloys are
made by pouring molten metal from a fine nozzle over a
cooling roller rotating at high speed, thus creating a ribbon(Fig. 9.12). At around 30-50μm, this ribbon is of a suitable
thickness for use as a head material; it is easy to make into alaminate core by layering it (Fig. 9.13).
Soft magnetic amorphous alloys are made from a
combination of ferromagnetic metals such as iron, cobalt
and nickel, and metalloids necessary for amorphisation,such as phosphorus, carbon, boron and silicon. Harder thanferrite at Hv=800+ and with the same or slightly higher
abrasion-resistance than Sendust, they are perfectly suitablematerial for audio heads. The higher performance amorphousFig. 9.13. Amorphous alloy ribbon (14)Fig. 9.14. Amorphous head (15)References
1)

Saishin Ōdio Gijutsu [Latest Audio Technology],
Ohmsha, April 1991, p. 156.

2)– 15) Takahashi, Shiro. “Jiki Heddo Zairyō no
Saikin no Dōkō [Recent Trends in Magnetic HeadMaterials]”, JAS Journal, 1981, Vol. 21, No. 10.

Historical Development of Magnetic Recording and Tape Recorder233

10 Development of Three-Head Compact Cassettes
10.1

Advantages of the Three -Head
Format

The two-head type is generally thought of as the standard
Compact Cassette. The idea is that the cassette is verticallysymmetrical and both sides can be used by turning thecassette over. This basic concept is very important, as it
rapidly boosted usability, providing tape recorders with anecessary and sufficient function. The basic specifications,such as tape speed, width and magnetic properties, werealso thought to provide sufficient functions for the expected
users and usage environment. Compact Cassette machines,
which had started out as simple “memo tape recorders”,
had successfully become the de facto standard. Once theycame to be regarded as mainstream tape recorders, rapid
technological developments took place to improve theirsound quality and performance. When improving theperformance of open-reel tape recorders, developers had beenquite free to select any tape speed as well as the shape andnumber of heads. Since it was straightforward to use heads
optimally designed for recording, playback and erasing, it
was inevitable that a three-head system was adopted. Of
course, even for open-reel machines, two-head systems weremore typical among popular-model machines and simple
head arrangements, such as DC erasing, were used in small,battery-operated machines. However, one major advantage inall of these machines, from popular-model machines to highperformance machines and even business machines, was that
there was free choice in terms of heads. In practice, moststereo tape decks used the three-head format.
While the main aim of the three-head format was to improve
the sound quality when recording, a major advantage wasthat running the playback head during recording made it
possible to have a “recording monitor”. When recording
on ordinary two-head tape recorders, the sound from themicrophone or line in was adjusted as necessary using
a preamplifier then sent to the recording amplifier. The
sound monitored during recording was the output from thepreamplifier, or the “sound being recorded”. Of course, somemachines had level meters for adjusting the volume and otherfunctions that made it easier to produce a better recording,such as automatic levelling functions, but ultimately, therecording could only be checked by rewinding and playing
back the tape after recording. While this presented no real
problems in general use, in instances where the recording
was vital, such as live recording, being able to monitor
the recording, or the “recorded sound”, during recording
provided a definite way to check the recording levels and234

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

to check for any flaws in the basic components, such as thetape or heads, thus providing a very effective way to prevent
mishaps. Monitoring during recording can only be achievedby having a three-head system with dedicated recording andplayback heads. This is the “three-head” format. For openreel systems, the head arrangement could be freely designed
to suit the required performance and functions.

10.2

T h re e - H e a d Fo r m a t fo r Co m p a c t
Cassette

The Compact Cassette running system serves as a taperecorder by inserting heads and a pinch roller into thecassette. Fig. 10.1 shows the main components of a typicalCompact Cassette tape recorder running system. There arethree large apertures (generally called “windows”) on theface of the cassette for inserting the heads and the pinchroller. The central window has a felt-like component calleda pad behind the tape, held in place by a leaf spring. Whenthe head is inserted, this pad pushes the tape against thehead to ensure contact is maintained between the tape andthe head. Fig. 10.2 shows the face of a cassette. The left
and right windows, for the erase head and the pinch roller,
are symmetrical, so that when the cassette is turned over,they each insert into the opposite window on the so-called
B side. These pinch roller windows are the large windows;
there are also smaller apertures between these large windows
and the central head window. These are the small windows;
while they are designed to have various uses, such as using
tape tension to detect the end of the tape and detecting thetransparent leader tape (the start and end of the reel of tape,mostly with no magnetic substance on it), they are hardly
ever used.

Pad
Reference
holes
Tape guide
Tape
guide

CapstanErase head
Pinch roller

Recording/playback headFig. 10.1. Diagram of the relative positions of the cassetteand structural components (1)LargewindowsSmallwindows

Fig. 10.2. Apertures on the face of a cassette

Given these constraints, it is difficult to implement a threehead format on a Compact Cassette and work out whichhead to put where. While various companies investigatedvarious proposals (Fig. 10.3), the first format implemented
used a system of standalone heads as shown in Fig. 10.3 (1).

Erase head

Playback
Recording
Tape guide
head
head

Erase head

Recording/playback
combination head

Tape guide
Erase head

Recording/playback
head

Monitor head

Although this format meant that heads very similar to theexisting recording/playback heads could be used as playbackheads, it was difficult to get any performance out of therecording head, as it had to be made smaller in order to fit
into one of the small windows. Since the small windows hadno tape pads, it was also difficult to maintain contact between
the head and the tape. As a result, a high-end running systemcalled a closed loop dual capstan had to be implemented tomaintain tape tension within the loop (the area between thetwo capstans) to ensure recording performance. The erase
head was placed on the outside of the upstream capstan; thishead also had to have quite a special shape to prevent it frominterfering with the pinch roller.
This three standalone head system was first incorporated into
the Nakamichi 1000 (Fig. 10.4) by Nakamichi Corporation.
This was an ultra-high-end tape deck with a price tag ofover ¥200,000 when it first went on sale in 1973. Major taperecorder companies such as Sony and Matsushita were also
working on similar developments around the same time;Sony released the TC-6150SD (Figs. 10.7, 10.8) in 1973,
while Matsushita released the RS-690 (Figs. 10.5, 10.6) in
1975, both decks with three standalone heads. This provedthat the Compact Cassette could have the same level of
performance as open-reel machines. Users gained confidence
that it could cover all areas from taking memos to highperformance, again boosting the popularity of the Compact
Cassette.

(1) Three standalone heads format- Optimal head performance- Requires specially-shaped heads(2) Combination head format- Easy to access each head
- Manufacturing of a combination head is key(3) Monitor head format- Recording/playback performance identical to thetwo-head format- Monitoring function during recording has been
added

Fig. 10.3. Proposed three-head arrangements (2)Historical Development of Magnetic Recording and Tape Recorder235

Capstan

CapstanErase head

Flywheel

Playback
Recording head
head

Pinch roller
Flywheel

Pinch roller

Fig. 10.8. Schematic diagram of the TC-6150SD
running system and head arrangement (7)Fig. 10.4. Nakamichi 1000 (1973) (3)Upright style with the cassette inserted upside down

Fig. 10.5. Matsushita RS-690 (1975) (4)Mechanism and amplifier are separate

Erase head

Recording head

Playback headFig. 10.6. Heads used in the RS-690 (5)Fig. 10.7. Sony TC-6150SD (1973) (6)The standard horizontal cassette deck of the day

236

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

The three standalone heads format was optimised for
performance. While it answered the call for the Compact
Cassette to function as a music player, cost was a major
limitation due to the special head shape; it was difficult
to develop a low-cost model. As the recording head wasinserted through the small window, it was sandwiched in
the relatively narrow space between the guide pins on thecassette side, making it difficult to maintain precision in tapeoperation and contact between the head and the tape. As aresult, the cassette was susceptible to azimuth loss during
recording and playback and spacing loss during recording.
The difficulty in maintaining mechanical precision and theadjustment processes required during manufacture only
added to the cost. If a three-head system could be achieved
using heads similar in size to the standard recording/playback head, then the same mechanism could be used,meaning a major reduction in cost. A “recording/playback
combination head” was developed, integrating the recording
and playback heads in one casing; this later became the main
three-head system in use. While contact between the tapeand the heads relied on a central pad, as it had previously,
the pad was smaller than before, with a width of 4-5mm.
It was therefore necessary to reduce the gap between
the heads to around 2-3mm, which required advanced
head processing technology. In the 1970s, the design andmanufacturing technology for such electronic devices wasquite advanced in Japan, meaning it was possible to produce
a superior combination head (Fig. 10.9). The combination
head had to accurately integrate the respective track heights(positions) for recording and playback, while at the sametime eliminating any difference in head protrusion (front
position) and also preventing azimuth loss by minimising therelative angle deviation between the two gaps. Accuracy had
to be maintained on all these fronts during manufacturing
and assembly. Another type of head – the “independent
suspension type” – required such precise processing methods
as well as azimuth adjustment following assembly (Fig.
10.10).

References
1)

Tēpurekōdā no Kiso [Tape Recorder Basics]. Sony
(Inc.) Technology Education Center, May 1985, p.
285.

2)
Fig. 10.9. Early combination headOki et al. National Technical Report Vol. 22, Panasonic(Inc.), August 1976, p. 425.

(8)

3)

“JAS Jānaru Tokubetsu-gō: Tokushū Ōdio no Seiki[JAS Journal Special Issue: A Century of Audio]”, JAS
Journal, 2001, Vol. 41, No. 10, p. 58.

4)Oki et al. National Technical Report Vol. 22, p. 423.

5)

Hirota, Nakata. National Technical Report Vol. 22,
Panasonic (Inc.), August 1976, p. 367.

6), 7) Provided by Sony Corporation.
8)
Fig. 10.10. Independent suspension combination head (9)Factors such as track position and head protrusion
are integrated into the assembly, then the record
head azimuth is adjusted after the set is completed

Hirota, Nakata. National Technical Report Vol. 22, p.
367.

9)

Takahashi, Shiro. “Jiki Heddo Zairyō no Saikin no
Dōkō [Recent Trends in Magnetic Head Materials]”,
JAS Journal, 1981, Vol. 21, No. 10.

Historical Development of Magnetic Recording and Tape Recorder237

11 Noise Reduction Systems
Compared to the popular open-reel tape recorders, theearly Compact Cassette machines performed too poorly
at recording music to be placed among the ranks ofserious audio equipment. Chapters 8 to 10 discuss theactive development undertaken to improve the heads andthe magnetic substance on the tape in order to boost therecording performance. However, one major factor in
Compact Cassette machines gaining acceptance as proper
audio equipment was the success of the noise reduction
systems that began to be used in household tape recorders asa means of increasing the dynamic range by expanding thesignal to noise ratio (S/N). When listening to sound recorded
on tape, there was sometimes a bothersome hissing noise.
This was often particularly noticeable when the music oraudio was very quiet (low level); this is called a hiss noise
and is quite audible because it largely comprises highfrequency components. The simplest way to reduce thisnoise is to cut out the high frequencies with a filter; however,this also cuts out the high-frequency component of thesignal (music), resulting in a muffled sound with a narrower
frequency response. One characteristic of the human ear isthat background noise is very audible when listening to lowlevel sounds, although it is hardly noticeable when listening
to loud sounds. It is possible to utilise this effect whenrecording quiet sounds by increasing the volume during
recording and then decreasing the volume during playback,effectively playing back the sound in its original state andsuppressing only the noise. In other words, this is a processof compressing/expanding the sound during the recording
and playback processes. US company Dolby Laboratories,
Inc. applied this principle and perfected a system that could
be put to use in a business tape recorder. In 1966, British
company Decca introduced the system for their in-housemaster tapes. This system, called the Dolby A, split the
20Hz-20kHz frequency range into four bandwidths, gaining a
10-15dB improvement in the S/N ratio through compression
and expansion in each bandwidth.

the ear. This side effect was a relatively minor problem if
there were favourable noise conditions to begin with, but
the strict Compact Cassette standards meant that they werevery noise-prone. This made the sound distorted and muddy,
which was difficult to correct by a masking effect alone. The
Dolby A system was also complex in its circuitry, with thefrequency range divided up and different operations for eachbandwidth. Another issue was that this also cost a lot. The
sensitivity of the human ear to different frequencies is wellunderstood through the so-called “Fletcher-Munson curves”;
there is actually a limited bandwidth that the ear hears
well. Fig. 11.1 shows that humans are sensitive to sounds
around 1-6kHz and less sensitive to higher or lower sounds.
The Dolby B system achieved effective noise reduction bytargeting and compressing/expanding sounds in this rangeof sensitivity as a countermeasure for the tape recorder hissnoise.

Intensity level [dB]

I n t ro d u c t i o n o f N o i s e R e d u c t i o n
Systems

Frequency [Hz]Fig. 11.1. Fletcher-Munson equal-loudness contour (1)Input

Output

Level

11.1

Frequency
Frequency
Fig. 11.2. Decoding using the whole-bandwidth level

11.2

Dolby BThe Dolby A system worked by compressing/expanding
the entire sound bandwidth. While this method was easy
to implement, it meant that the whole bandwidth would bemanipulated even if only one frequency band had a highlevel signal. This meant that the background noise would
audibly fluctuate, resulting in a sound that was unnatural to238

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

compression method (2)InputLevel

OutputFrequency

Frequency

Fig. 11.3. Decoding using the sliding-band method (3)Fig. 11.2 shows the playback frequencies when the wholebandwidth level compression method is used. The signal isexpanded irrespective of frequency. In such cases, if there
is a high-level signal at particular frequency, the entire
bandwidth is subject to compression/expansion, resulting inless effective noise reduction. By contrast, Fig. 11.3 shows
the playback frequencies when the “sliding-band” method
adopted by the Dolby B system is used. The high-frequency
range is expanded a fixed amount according to signal level.
Even if there is a loud signal in the low- and mid-frequency
range, a fixed amount of attenuation is ensured in the highfrequency range, which also suppresses other side effects,
such as breathing*.
By keeping compression/expansion to a minimum, the Dolby
B system prevented other side effects and was also relatively
cost effective. As a consequence, it became widely used as anoise reduction system for the Compact Cassette. However,since it manipulated the signal in a relatively moderatemanner, the resulting noise reduction effect was not all thatlarge, usually around a 10dB improvement in the S/N ratio.
As the digital audio era approached, further competition
ensued to develop more effective noise reduction systems.
Fig. 11.4 shows a comparison between the effect producedby the Dolby B and the more effective Dolby C, which wasintroduced later.

* When a signal-compressing/expanding noise reduction
system such as the Dolby encounters a signal that varies
greatly at a certain frequency, the noise reduction effectfluctuates as compression/expansion is carried out in
response to this signal. This results in a fluctuation inbackground noise, which is unnatural to the ear. Thisphenomenon is called breathing.

11.3

Growing Popularity of Dolby Noise
Reduction (NR)The Dolby B noise reduction (NR) system was first released
as a standalone unit, but it soon became incorporated intocassette decks. The first cassette deck with an inbuilt Dolby
system was put out by TEAC in 1971 (Fig. 11.5). The Dolby
B system suddenly grew in popularity as a standard cassettedeck feature, with Sony releasing its first cassette deck withan inbuilt Dolby system, the TC-2250SD (Fig. 11.6), in 1972.

Fig. 11.5. Cassette deck with inbuilt Dolby B system
TEACA-350 (1971)

1/3 octave band noise level [dB]0dB=160mWb/mNR OFF

Dolby•B

Dolby•C

Metal tapeFrequency [Hz]Fig. 11.4. Dolby noise reduction effects (4)Historical Development of Magnetic Recording and Tape Recorder239

While the Dolby B gained popularity as the de facto
standard system, other competing systems were developed
and put to use, as outlined below.

11.4.1 ANRSJVC developed its own four-channel stereo record, the“CD-4”. It also developed its own noise reduction systemin the ANRS (Automatic Noise Reduction System) format
as a means to reduce the noise of the difference signal
recorded in the UHF range to produce a rear signal. JVC
cassette decks started being produced with an inbuilt

240

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

m

Co

sor

s
pre

2)
(1/
)

Other Formats

dB

r (2

11.4

11.4.2 dbx
dbx is a noise reduction format developed and released byAmerican company dbx, Inc. in the early 1970s. It started
out as a high-performance noise reduction system forbusiness machines to rival the Dolby A system. Designed
to work across a wide range of frequencies and levels, its
compression/expansion worked in a logarithmically linear
manner. Fig. 11.7 shows input and output using the dbx
format. Since any signals above 0dB are attenuated, it could
compensate for any tape saturation and could produce drastic
noise reduction, meaning it was superior in many ways.
However, it was very difficult to incorporate the system into
any popular-model tape recorders, as the circuit was complex
and costly and uniform compression/expansion was carriedout regardless of signal level or frequency, meaning it would
be susceptible to breathing in machines with poor basic
performance. An increasing number of manufacturers began
to use it in high-end cassette decks due to the good soundquality and drastic noise reduction effect; to some extent, it
gained a reputation as offering higher-end NR than Dolby. It
gained relatively wide acceptance in the world of businessmachines and was often used by companies such as recording
studios. While the introduction of music tapes presented no
obstacle to the system, it was never put to use in consumer
machines and gradually disappeared off the market.

O
sy verste al
m l
(in
Exp
pu
and
t)
e

Following the development of chrome tape, the Dolby
NR system played a huge part in improving recording
and playback performance. It later became monumental
in tape recorder development history as having elevatedthe Compact Cassette from a memo recorder to a serious
piece of audio equipment. While compressing/expanding
noise reduction systems such as the Dolby are expected tohave a greater effect and ensure a better sound quality thansimply cutting noise with a filter, tapes with compressedrecordings on them lose their compatibility, as they must
be expanded and played in a predetermined manner.
When the Dolby B came to the fore, it had no obvious
rivals; it had the good fortune to take hold as the standard
system in a relatively smooth manner. While Dolby
Laboratories, Inc. started out in technology development,
the company also became well-known for its successful
licencing business model, having employed some clevertechnology agreement strategies when the Dolby NR
system became popular. Although various other systems
were later developed for noise reduction and some market
competition ensued, the Dolby B continued to be usedthroughout as the standard NR system. The fact that its
successor, the Dolby C, kept a number of rivals at bay
and maintained its position as the standard system wasprobably due to a sense of security associated with thename “Dolby”.

Output level [dB]Fig. 11.6. Sony TC-2250SD (1972)

ANRS system not long after the Dolby B appeared. Although
ANRS was JVC’s own technology, it operated very similarly
to the Dolby B system and the two were thought to becompatible. Dolby carried out negotiations with JVC on the
ANRS format in order to promote standardisation and ensure
patent licencing fees, but in the end it accepted the originalityof ANRS and formally acknowledged its compatibility with
Dolby B. Many JVC ANRS cassette decks had NR switcheslabelled “ANRS/Dolby B”, indicating that there wascompatibility between the two.

-60

no

u

ed

r
ise

ine

nl

o
cti

Interim transmission
noise -60dB (assumed)

Input level (dB)
Fig. 11.7. Input and output properties using dbx format (5)11.5

Noise Reduction Development

The Dolby B, ANRS and dbx systems were incorporated
into cassette decks relatively early on. While this contributed
to the Hi-Fi capabilities of the Compact Cassette, as the
adoption of digital audio became an increasing reality
from the late 1970s onwards, the Compact Cassette had tofurther expand its dynamic range, in other words, increase
its noise reduction effect. Every Japanese manufacturer at
the time developed and released its own noise reduction
system, working on its own developments as well as joint
developments with manufacturers in the West (Fig. 11.1).
Meanwhile, the veteran company Dolby announced the
Dolby C, the successor model to the Dolby B. The Dolby C
system ran two B-type operations in stages, expanding its
noise reduction range to lower frequency areas, producing
a noise reduction effect of 20dB or more. Comprising two
B-type circuits together, as shown in the block diagram in
Fig. 11.8, the C system could also operate as a B-type system
by running only one phase on one circuit. Not only was it
easy to switch between B and C operation, there were also
obvious cost benefits to combining it all in an integrated
circuit. While it offered less in terms of noise reduction andtone sensitivity compared to other formats, it performed at
an adequate level to be used as a Compact Cassette noise
reduction system in the digital audio era. Given the degreeof familiarity with the “Dolby” name, many manufacturers
deemed it beneficial to adopt the Dolby C system; thus, theDolby C secured its place as the de facto standard system.
When CDs appeared in 1982, the audio world immediately

became digitised and the Compact Cassette sound quality
competition came to a standstill, although the Dolby C kept
its popularity in the field of high-end machines.
This competition between NR systems prompted thedevelopment of secondary functions in cassette decks tomake NR systems work more accurately, thereby playing
another role in improving the performance of cassette decks.
Compact Cassette noise reductions systems all worked on
the basis of compressing and expanding analogue signals.
The operating principle was that tape recorders had uniform
recording and playback properties, that is, the signal level
during recording and playback was identical and that thefrequency response was even. When this assumption wasdisproved, there was a fear that the difference in levels would
increase through compression/expansion. Any disparity infrequency response potentially meant that the NR could
malfunction. While there was a certain degree of tolerance
in the precision and stability of Compact Cassette machines,
if different tapes were to be used, there would be subtle
differences in sensitivity and frequency response, dependingon the tape. To prevent this variability, the drawback of noise
reduction, and to ensure high sound quality through precise
operation, high end machines appeared equipped with a“calibration function” for each tape. These machines had astandard signal generator inside them and could provide leveladjustment for recording and playing back each tape; thefrequency response could also be adjusted according to theamount of bias. Some of these sets were operated manually,
while some sets were developed that used a CPU to makethese adjustments automatically.

Fig. 11.8. Dolby C block diagram (6)Historical Development of Magnetic Recording and Tape Recorder

241

242

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

No

RMS

Frequency division

Level detection

No
RMS

No

+6dB (10kHz)

Variable

Fast attack time

Not required

Fast attack time
Limiter

Breathingcountermeasures

Clipping

その他
Other

Not required

RequiredLevel matching
Required

100

300

Recovery time (ms)

1.5-2

1

Attack time (ms)LR separately
Level detection channel LR separately
Fixed+
VariableFixed+variable
Emphasis
variableNo

Variable

Compression /expansionCompression
properties
rate
High-levelcompression

Variable

10dB (5kHz+)
5dB (1kHz)

10dB (5kHz+)
5dB (1kHz)

NR Effect

Variable

VictorVarious

Local brandRelative
level
Relativefrequency

JVC

Dolby Lab. (UK)Super ANRS

Developer

ANRS

Dolby BNR Format

Not required

Not required

LR separately

RMS

Wide-range onlyNo

Variable

Expansion only
(variable)

1:2

1:1.5
Single band
control
RMS

Required
Reducecompression
ratioVariableemphasis

Weightingcircuit

VariableemphasisEmphasishigh-level
recording
Fast attack time
Weighting circuit
Used in decks
with good frequency
response and levelvariations

100

Not required

Encoding 200
Decoding 400

several ms

200

High-level: fast
Low-level: slow

Bandwidth
split in two
Variable emphasis

Fast attack time

Bandwidth
split in two

WeightingcircuitLow-levelslow attack
time safeguards
group delay

High-level
fast attack
time

Required
Not required
Not required
ReduceReducecompression ratio compression ratio Reduce
compression
Bandwidth
Bandwidth division ratio
division

1

No

L+R
Fixed

Variable

Variable

Fixed

1:1.5
Single band
controlPeak level

1:2
Split in two(48kHz)Peak response
LR separately

1:1.5

1:2

LR separately

NoNo

LR separately

Linear

20dB+

Lo-D

Hitachi

Lo-D CompanderLinear35-40dBLR separately

RMS

Split in two

1:2/1:1

1:1.5/1:1

1:2
1:2
Single band
control
RMS

Variable

Variable

Variable

Variable

20-25dB

30dB (10kHz)
20dB (1kHz)
17dB (100Hz)

Otto

ToshibaNakamichi
Aiwa

Sanyo

Telefunken /Nakamichi

Aurex

Super D

High-Com II

Adres

No

Linear

30dB+

TEAC

Hitachi /Toshiba /Nakamichi
15dB (10kHz+)dbx (USA)dbx II

Philips (Netherlands)

DNL

Table 11.1. Performance Comparison of Various NR Systems(7)References
1)

6)

Takasu, Daihachiro. “Waga-Sha no Noizu Ridakushon

Saishin Ōdio Gijutsu [Latest Audio Technology],

Shisutemu: Tiakku [Our Company’s Noise Reduction

Ohmsha, April 1991, p. 15.

Systems: TEAC]”, JAS Journal, 1981, Vol. 21, No. 10.

2), 3), 4) Shirai, Tatsuro. “Waga-Sha no Noizu Ridakushon
Shisutemu: Nihon Bikutā [Our Company’s Noise7)

50 Years of Audio. Japan Audio Society Publishing,December 1986, p. 512.

Reduction Systems: JVC]”, JAS Journal, 1981, Vol.
21, No. 10.
5)Kogure, Takuyo. “Waga-Sha no Noizu Ridakushon
Shisutemu: Matsushita Denki Sangyō [Our Company’s
Noise Reduction Systems: Matsushita ElectricIndustrial]”, JAS Journal, 1981, Vol. 21, No. 10.

Historical Development of Magnetic Recording and Tape Recorder243

12 Advances in Driving Motors
12.1

Early Mechanisms and Motors

The early Compact Cassette tape recorders were released
with single-motor mechanisms, aimed at maximising
functional performance, downsizing and simplifying (Figs.
12.1, 12.2). Since the overall machines could be madesmaller than the open-reel systems and could get by withthe minimum necessary power to drive the tape, developers
used low-output DC motors in them. However, the highperformance cassette deck followed on the tail of thesemachines and grew in popularity. To have the performanceand function of serious audio equipment, these tape recorders
had to meet higher standards than the small-scale machines
in terms of the accuracy and reliability of the machine itself.
While they still had the same tape recorder mechanisms
to play Compact Cassettes, these new machines were thesuccessor models. The early deck-type machines wereintended for use in the home; many of them had the AC
motors that were in standard use in the open-reel machines.
When the Compact Cassette appeared, DC motors wereused in toys and trivial consumer electronic goods; they had
hardly ever been used in audio equipment. By contrast, there
were already a number of superior AC motors designed foraudio systems, having been used in record players and open-

reel tape recorders. It was also very important for record
players and tape recorders to maintain an accurate rotation
speed, so hysteresis synchronous motors, which could rotate
in sync with the power frequency, were well suited to audio
equipment.
Rapid improvements were made to the overall design ofboth the deck-type and portable-type machines. The main
driving mechanism in both types changed from an AC
motor to a DC motor, due to the development of servo
motor technology to maintain a steady rotation speed
and successive developments on DC motors designed tosuit audio equipment. This resulted in greater reciprocalinteraction: the mechanism design required the motor to behigh-spec, as it was the core device; in turn, the mechanism
had to be more advanced to handle the new motor. The
Compact Cassette size restrictions would have been
another factor, as this would have naturally played a part indetermining the size of the mechanism and prompted theuse of small-scale DC motors. Among other factors, suitable
motors for audio equipment had to run smoothly and silently
with no rotational irregularities; they had to guarantee a long
operating life of at least 1000 hours under a certain load; they
had to produce minimal electromagnetic noise and readily
produce a prescribed rotation speed.

Fig. 12.1. Inside of an early cassette tape recorder (1)244National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

Capstan motor
Reel stand L

Reel stand R

FlywheelFig. 12.2. Basic single-motor tape deck mechanism (2)12.2

Servo Motor Development

Many of the DC motors used in the early Compact Cassettemachines had mechanical governors as a means to attainfixed speeds. A mechanical governor is a switch that uses
centripetal force generated in proportion to rotation speed
to automatically turn the power supply to the motor on oroff (Fig. 12.3). The counterweighted governor is directly
connected to the motor’s rotational axis; as the rotation speed
increases, the centripetal force makes the counterweights
move along the outer circumference, thereby braking
a connection. The current stops and the rotation speed
decreases. If the rotation speed drops below a certain limit,
the centripetal force decreases and the connection is made;the current resumes once more. Repeated tens to hundredsof times per minute, this operation serves to maintain afixed rotation speed. Although it is a relatively simple, lowcost mechanism, it is prone to generating electrical noise as
the connection joins and breaks. Furthermore, if constant
speed is a strict requirement, it becomes very complicated toregulate contact pressure and other factors, which affects thereliability and longevity of the device. While only average inperformance, such motors were often used in popular-modeltape recorders because they were simple and cheap.

Fig. 12.3. Mechanical Governor (3)The governor motor had limitations to the constancy of speed
it could produce; it also generated electrical noise and wassomewhat unreliable. In light of these factors, efforts weremade to introduce servo technology, as this was capable ofproducing a higher-performance motor. Servo motors workby detecting rotation speed with a sensor and then usingthat information to perform feedback control on the driving
current. A frequency generator (FG) was developed to be
used as a sensor, working on the same principle as an AC
generator. The FG principle comprises a multiple-pole ringmagnet being rotated to induce an alternating current of afrequency corresponding to the rotation speed in a coil woundaround a comb-shaped sensor. If the number of N poles isdesignated as N and the rotation speed as X rps, the current
generated corresponds to N x X Hz. Figs. 12.4 and 12.5 show
the structure and principle of FG. Fig. 12.6 shows the internal
workings of an actual motor with a FG incorporated.

Fig. 12.4. Complete FG and comb-shaped
sensor component structure (4)Historical Development of Magnetic Recording and Tape Recorder245

90 pairs of magnetic
poles formed within
a ring-shaped magnet

450(rpm)=7.6(rps)7.6(rps)×90=684(Hz)Arm
Head (90 pairs ofmagnetic poles in total)

Fig. 12.5. Diagram of the FG principle (5)FG component

Fig. 12.6. Example of a standard DC motor (6)The FG output signal varies as shown in Fig. 12.7 (1) as
the rotation speed varies. It takes the form of a combinationof AM modulation, in which the amplitude changes inproportion to the rotation speed, and FM modulation, in
which the frequency changes in proportion to the rotation
speed. The AM control signal method was often usedin devices where cost was a major factor, as it could beachieved with a relatively simple electronic circuit, but it
was not capable of demonstrating the full capabilities of thehighly-anticipated FG. By contrast, the method shown in Fig.
12.7 used to achieve a control signal through FM was calledfrequency control. It was often used in high-end machines
such as tape decks as, although costly, it was fully capable ofhigh servo performance.
Cassette deck mechanisms started out as basic, singlemotor devices and developed into two-motor devices withindependent motors for driving the reels, as shown in Fig.
12.8. This format enabled the dedicated use of the capstandriven motor, which was key to precise tape feeding, making
it possible to achieve high performance. A “direct drive”
type was also developed, which had the capstan directly
connected to the motor axis.
Reel stand L

The size and frequency of the voltage generated are inproportion to the rotation speed and either can be used as acontrol signal. By increasing the number of magnetic poles,
it is possible to increase the accuracy of the sensor and gaina high-frequency signal even with a low rotation speed.
However, if there are an excessive number of magnetic
poles, the output decreases and the S/N ratio gets worse,
thus reducing the reliability of the sensor. Consequently,
an appropriate FG with an appropriate output suited to therotation speed used should be incorporated into motor design
and assembly.

Reel motor

Capstan motor
Reel stand R

Flywheel(1) FG output
signal wave

Fig. 12.8. Basic two-motor tape deck mechanism (8)12.3Standard voltage Vs(2) Control signal
output wave

Fig. 12.7. FG output signal processing (section) (7)246

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

Direct Drive Motors

The direct drive system, with the capstan directly connectedto the motor axis, was suited to audio equipment, as it
could produce a low rotation speed with minimal vibration
or operating noise. It was also simpler and more reliable
than other indirectly-driven systems, which used a powertransmission mechanism such as a belt or idler as a
reduction drive for the capstan. However, indirectly-driven
systems allowed the rotation speed to be set at a more
efficient rate and made it easier to maintain driving torquethrough deceleration. They were likely to be used in small,inexpensive motors, giving a greater freedom of choice
in motor selection. On the other hand, since intermediarycomponents were used in power transmission, the overall
structure of servo driving systems was more complex,
making it a little more difficult to operate the control system
to its full capacity. Direct drive systems were quite theopposite: they were mechanically simple and readily allowed
accurate servo control. A large-diameter flywheel could
not be used where there was a low rotation speed, or in a
Compact Cassette tape recorder, so moments of inertia were
not a reliable option. It was therefore necessary to design the
motor making the output frequency of the FG that detects
the capstan rotation speed as high as possible, widening
the servo bandwidth and making the rotation as smooth as
possible. This required a brushless motor, which, although it
was not cost-effective, was designed for use in high-end taperecorders.
Open-reel machines had quite spacious mechanisms, with agreater degree of freedom in terms of the drive system designand choice of motor; hardly any of them used a direct drive
system. Direct drive motors were probably first developedfor use in record players. Matsushita developed a low-speed
brushless motor for record players quite early on; this “directdrive” technology was then able to be used in the smallercassette decks at an early stage as well. In 1970, the RS272U (Fig. 12.9) became the world’s first cassette deck withan inbuilt direct drive system.

with the NHK Science & Technology Research Laboratories
to produce the DL-103. Although they developed thiscartridge in 1964 as a business-use device for use in FM
stereo broadcasting, it brought in a lot of interest fromaudiophiles who were impressed by the high sound qualityof the FM stereo broadcasts. The MC cartridge was released
in 1970 for consumer use and became well-loved throughout
the world as a high-performance device. Incidentally, it isstill being sold to this day. As well as developments to thecomponents in the transducer unit, such as the cartridge andthe tonearm, developments were also taking place on theturntable drive mechanism, with remarkable improvements
being made in performance, such as progressing from theidler drive to the belt drive and introducing servo technology.
Matsushita developed a low-speed brushless DC motor quite
early on to be used in record players, announcing its brushless
DC direct drive phono motor technology in 1969. While
Sony also developed a direct drive phono motor around thesame time, this was an AC motor. Although Matsushita was
the first to announce direct drive technology, Sony released
the TTS-4000 (Fig. 12.12) and the PSE-4000 record player
system incorporating it in 1970, about one month earlier
than Matsushita released the SP-10 (Figs. 12.10, 12.11).
The world’s first direct drive phono motors appeared one
after another in Japan. For the first time, original Japanesetechnology was appearing on the world audio market.

Fig. 12.10. Matsushita direct drive turntable SP-10 (1970) (10)Fig. 12.9. Matsushita RS-275U (1970) (9)While record players already held the dominant position as
the main audio playback machines, a flurry of new technology
and product developments after the Second World War for
all components accompanied major breakthroughs such as
LP records and stereo-capable machines, making the record
player the most important item of home audio equipment. For
instance, while manufacturers in the West had always supplied
the best pickup cartridges, arguably the most essential
component for playback, many cartridge manufacturers
appeared in Japan from around 1960 and began to produce
cartridges that were just as good as their counterparts madein the West. In particular, Denon, which had played an activerole in the disc-style recorder industry before the war, worked

Position detection rotor
Position detection coil

Turntable

Rotor (magnet)
Turntable shaft

StatorFig. 12.11. Cross-section of a SP-10
DC direct drive phono motor

Historical Development of Magnetic Recording and Tape Recorder

247

12.4

Fig. 12.12. Sony AC servo-type direct drive phono motor
TTS-4000 (1970) (11)Armed with the DC direct drive motor, Matsushita wasable to take the top share of the world record player market.
It was also able to apply the same low-speed DC servo
motor technology to make a direct drive system for thetape recorder, thereby creating the world’s first direct drive
cassette deck. It also applied the technology to a singlecapstan, closed-loop, open-reel machine, releasing the highend, high-performance RS-1500U (Fig. 12.13) in 1976. Fig.
12.14 shows internal and external views of the direct drive
motor used in the RS-1500U.

Fig. 12.13. Matsushita RS-1500U (1976) (12)Fig. 12.14. RS-1500U capstan motor (internal and external views) (13)248

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

Development of the DC Brushless
Motor

As AC motors used induced currents and eddy currents,
induced in a rotor by a magnetic field, they had greater
torque uniformity. While this was good for sound, it meant
they lacked controllability. By contrast, DC motors weremore controllable, but they had greater fluctuations in torquecaused by the timing with which the magnetic poles turned tokeep the motor rotating. To prevent this required increasing
the number of magnetic poles, thereby evening out the torquegenerated by multiple poles. Accordingly, although the DC
motor presented more manufacturing issues than the AC
motor due to greater complexity in the field winding
structure, it was easier to increase its efficiency. As the DC
motor control circuit did not have to deal with large AC
currents, it was very compatible with transistor circuits. It
lent itself to being made smaller and lighter, making it a goodcandidate for small-scale devices. In fact, DC motors started
being used in most of the audio-visual equipment that was
brought out after this. In 1970, Sony released the world’s first
direct drive phono motor using AC to ensure rotational
torque stability. While this was used in basic player systems
for a time, the DC motor steadily became the standard.
With the move to DC, studies began on how to suppress
the fluctuation in torque occurring with polarity changes in
the magnetic field. A driving method was developed thatgenerated torque in a theoretically linear manner rather
than increasing the number of magnetic poles. Generally,
the torque generated by a DC motor corresponds to the
product of the magnetic flux density (in the gap) between
the rotor and the stator and the current flowing through thecoil interacting with the magnetic flux in the gap. Where
the rotor is a thin, cylindrical magnet with multiple poles
magnetised in a sine wave in the radial direction, the stator
coils are positioned so that the two sets of poles have aphase difference of 45º. A Hall effect sensor is used as a flux
detector to ensure that the current flowing through the twocoils corresponds to the magnetic flux of the rotor. When thecurrent is linearly altered rather than switched, the torquegenerated by the first coil-magnet pair corresponds to thesquare of sin θ (where θ represents the turning angle of therotor). The remaining coil-magnet pair has a phase differenceof 45º, so the torque generated there corresponds to thesquare of cos θ. In theory, the torque then remains uniform,
since the torque generated between the two corresponds tosin2 θ + cos2 θ = 1 (Fig. 12.15). This type of motor is called
the BSL (Brush & Slotless) motor; it was developed to be themain motor used in mid- to high-end audio equipment. First
used as a direct drive phono motor for record players, its
scope of use soon expanded to cassette deck standard motors(Fig. 12.16) and direct drive capstan motors. An OTM (one

sensor two phase) type was also developed, which combined
this with a pole detection sensor; this arrangement was used
to slim down the Walkman.

Direction of rotation
N.S. formation magnetisedby the rotating body
Coil force

Ferrite rotating
body (rotor)(Turns together)(Coil affixed to base)

Hall effect sensor(Switches coilcurrent direction)

Coil affixed to metal base(Two black coils and two white coils form a set.
Arrows show the current direction.)Fig. 12.15. Diagram of the BSL motor principle (14)simple as possible, with mechanical governors for speed
control and back EMF control. However, the standard
iron-core motors were limited in terms of their size andelectricity consumption. It was deemed necessary toincrease the performance of the set with each enhancementin functionality. Small-diameter, coreless motors weredeveloped around this time and began to be used in handheld
tape recorders. The overall performance of the motor rapidly
improved, not only in terms of electricity consumption, butalso in terms of less mechanical and electrical noise andgreater reliability. This greatly boosted the product value ofthe small-scale tape recorder.
While the rotor in an ordinary small-scale DC motor consistsof a coil wrapped around a core, the rotor in a coreless motor
consists of a cylindrical, “cage-like” coil; this is also called amoving coil (MC). As no eddy-current loss (core loss) occurs
when the rotor turns, it is theoretically more efficient. Otherchanges were incorporated into the design to make it more
efficient overall, such as using rare-earth magnets to generate
torque even with small diameters, or narrowing the space inwhich the rotor turns to increase the magnetic flux density.
These were also produced with inbuilt FGs and also used in
servo control (Fig. 12.17). For more information on smallscale, handheld devices using small-scale coreless motors,
see the discussion in Chapter 6 on product developments
related to the Walkman.

Rubber isolator
Yoke
Rotor coil
Vibration-proof,
soundproof casing

Fig. 12.16. Standard BSL motor

12.5

Rare-earth magnet
Frequency
generator magnet

Coreless Motors for Por table
Machines

Small-scale tape recorders made good use of the size of theCompact Cassette, developing into far more fascinatingproducts than had been seen in the open-reel era. Thisnew type of small-scale tape recorder focused on being
small, lightweight and easy to use rather than being HiFi capable. They were also mostly battery-operated, soelectricity consumption was a major factor for consideration.
Reducing the electricity consumption of the motor wasa very significant issue. To start with, standard iron-corebrushed DC motors were used in small-scale tape recorders.
Motors were selected on the basis of being as small and as

Frequency generator coilBrush
Commutator

Fig. 12.17. Structural diagram of a small-diameter coreless motor

References
1)Mori, Yoshihisa, et. al. Onkyō-Gijutsu-Shi [History ofSound Recording], Tokyo University of the Arts Press,
March 2011, p. 91.

2)

Saishin Ōdio Gijutsu [Latest Audio Technology],
Ohmsha, April 1991, p. 171.

Historical Development of Magnetic Recording and Tape Recorder

249

3)

Tēpurekōdā no Kiso [Tape Recorder Basics]. Sony
(Inc.) Technology Education Center, May 1985, p. 173.

250

8)

Saishin Ōdio Gijutsu [Latest Audio Technology],
Ohmsha, February 1995, p. 171.

4)

Ibid., p. 209.

9), 10), 12), 13) Provided by Panasonic Corporation.

5)

Ibid., p. 209.

11) Provided by Sony Corporation.

6)

Ibid., p. 207.

14) Tēpurekōdā no Kiso, p. 220.

7)

Ibid., p. 217.

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

13 Towards the “Headphone Stereo”
13.1

Popularity of R adio and Home
Audio

Thus far, listening to music on audio equipment had beena pleasure to be enjoyed at home. Ever since Edison andBerliner invented the phonograph and gramophone, music
had been listened to in the living room, recorded on themedium of records. Of course, venues such as restaurants
and bars also used music products to entertain their guests,
providing background music or music for dancing. Certain
shops also specialised in providing certain styles of music
for listening, such as jazz or classical. In any case, whether
it was played for the purpose of listening to “good music” orfor creating a “pleasant environment”, it was always playedindoors on large, bulky equipment.
Radio broadcasts began in the 1920s and rapidly gained
popularity throughout the world, starting in the West andspreading to Japan. Broadcasting was done through cuttingedge wireless technology; it was a ground-breaking meansof transmitting information to the masses and people became
enthralled by radio news broadcasts. Radio broadcasts
could also transmit music, something that was absolutely
impossible through paper media such as newspapers, so it
was not surprising that listeners readily welcomed musicalbroadcasts from the beginning. While the gramophone and
SP records had already enjoyed some degree of popularity
before radio broadcasts began, playing music had not really
become a true form of mass entertainment, as one record
could only play for ten minutes or less and gramophones
and records were expensive. When radio broadcasts began,
the record industry was afraid that radio was encroachingon its domain; however, the outcome was the complete
opposite: repeated radio programmes were very popularwith listeners and prompted a major increase in gramophone
and record sales. Trend-setting radio broadcasts and records
for playing music had a mutually beneficial effect on eachother, creating a “home audio” culture. While pre-war radio
broadcasts in Japan focused on providing information,such as news broadcasts, after the war there was a growinginterest in musical broadcasts, inspired by the AFN (American
Forces Network)* for American troops in Japan. Not longafter the war, the AFN became a major presence in Japan,
having given rise to a large number of music fans andaudiophiles. At this time, the AFN was drawing on discstyle records recorded in the United States for its source ofmusic; Japanese audio engineers were profoundly inspiredby listening to the tremendous radio sound quality affordedby American recording and broadcasting technology, the bestin the world. Commercial broadcasting began in 1951 andfurther developments continued on music broadcasting inJapan.
* AFN: Broadcasts for American troops, known as the FEN (Far
East Network) in Japan until 1997.

13.2

Higher Quality Radio Broadcasts

LP records were released in Japan in 1951. These records
were highly regarded by audiophiles not only for theirlonger playing time, but also for their high-quality sound.
High-quality music playback became popular immediately,
resulting in a growing dissatisfaction with the quality of radio
broadcasts. At the time, radio broadcasts were medium-wave
AM broadcasts. While various efforts were made to raise
the quality, such as introducing stereo broadcasts using two
AM stations, as television broadcasts gained in quality, AM
radio music programmes ended up being mainly so-called“disc-jockey” programmes intended for car radio or portableradios. High sound quality was delegated to FM broadcasts.
By 1940, there were already around 30 FM radio stations
operating in the United States. FM broadcasting began tospread in earnest from 1955, when the FCC (the UnitedStates Federal Communications Commission) approved
the transmission of news and background music using
FM multiplex broadcasting sub-channels. In Europe, West
Germany planned to cover the entire country with FM,
having had its medium-wave frequency allocation reduced
following its defeat in the war. These broadcasts began in1945 and soon their superior sound quality attracted theattention of countries such as the United Kingdom andFrance, thus spreading the popularity of FM broadcasting.
In 1957 and 1958, the NHK opened experimental stations
in Tokyo and Osaka, while experimental commercial station
FM Tokai started broadcasting in 1960. The Japanese hadgreater hopes for high-quality broadcasts than the noiseand interference-ridden broadcasts in the West; Japanese
broadcasters set their sights on Hi-Fi music broadcasts fromthe start. In 1956, the 45/45 stereo LP record took hold in
the industry, but stereo records were very highly priced
for everyday users at the time. Many audiophiles eagerly
awaited FM stereo broadcasting. On 17 December 1963,
the NHK made its first FM stereo broadcast. The first song
was Mozart’s Symphony No. 40, performed by the Vienna
Philharmonic Orchestra and conducted by Herbert von
Karajan. The preparations for FM broadcasting in earnest
had thus been steadily laid. From 1969 to 1970, the NHK andHistorical Development of Magnetic Recording and Tape Recorder251

commercial broadcasters began proper broadcasts, usheringin Japan’s FM age in earnest.

13.3

Music Broadcasts and Recorders

The commencement of proper FM broadcasting coincided
almost perfectly with the appearance of Compact Cassettetape recorders. These tape recorders received muchattention as being capable of recording high-quality musicalbroadcasts. The NHK and many other interested parties had
put a lot of effort into the sound quality of FM broadcasts,
while Japanese audio manufacturers had competed ruthlessly
to develop the receivers. As a result, FM broadcasts werea fairly high quality source of music. At the time, highend, open-reel tape recorders were considered suitable
for recording music and the use of a deck-style machinein conjunction with stereo equipment became a favourite
among audiophiles. Since FM stereo broadcasts have a
19kHZ stereo pilot signal and acoustic properties extending
to approximately 15-16kHz, (in terms of specifications) the
open-reel machines had to perform in four-track stereo at
19cm/s. Reverse machines were also well-received, capableof long, continuous recording of music broadcasts. Openreel decks reached a height of function and performance inthe early 1970s, when the so-called unattended recording
function was added to record desired programmes from FM
broadcasts. By contrast, the Compact Cassette served as amemo recorder and was thought to be incapable of proper
Hi-Fi music recording. However, its ease of use, potential
for downsizing and firm position as the de facto standard
were enough to show promise for the future. Efforts wereredoubled to produce technology capable of high quality
sound and somehow rival that of the open-reel machines.
Within a short time, the Compact Cassette had earned its own
place as a serious piece of audio equipment. (See Chapters 8
to 12.)

13.4

Transition towards Personal Audio

Another factor contributing to the popularity of radio
broadcasts was the personalisation of the audience. Listening
to the radio or playing music on records was entertainment
enjoyed in the living room together as a family. For a longtime, it was normal to have one piece of audio equipment perhousehold. When stereos started becoming popular in Japan,
most of them were bulky pieces of household furniture,whether they were ensemble devices or separate devices.
However, Japan took the lead in downsizing this equipmentusing transistors, opening up a market for portable audio
systems quite early on. Once these portable radios became
affordable in the 1960s, disc jockey programmes in the formof late-night broadcasting became immensely popular with252

the younger generation; programmes aimed at these young
people introduced new musicians and the latest pop musicfrom overseas, playing a major role in in the spread of music
culture and the expansion of the record industry. There wasa growing interest in FM and FM stereo broadcasts fromusers accustomed to listening to music on small-scale radios
seeking a better and more impressive sound. While they
preferred high-quality radios and stereos, the price of proper
audio equipment was too high for young people to personallyafford.
Consequently, although music was growing in popularity,
young people could not afford records and audio equipment.
This all changed with the appearance of the “radio cassette”.
This machine could have been called a modern gramophone– a device incorporating a small-scale Compact Cassette taperecorder and a radio capable of FM reception together in one
unit with an inbuilt amplifier and speaker. This concept andthe attractive price meant that it received tremendous backing
as a personal audio device for young people. It could reliably
record FM broadcasts onto Compact Cassette and play themback quite simply for repeated listening. Such ease of use
was one of the major advantages to this device. It continued
to develop into a serious piece of sound equipment,
successively incorporating stereo capabilities, loud volume,
double cassettes and CDs. The progress from radio to radio
cassette player was one clear step in the personalisation ofaudio. The image of audio equipment for individual use
shifted from that of tape recorders for recording or radios for
information gathering to that of devices for enjoying musicby oneself. The radio cassette player progressed into a smallscale personal combo (a stereo for a child’s room); music
recorded on Compact Cassette could be built up into a wealthof soft assets at the user’s disposal.

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

Fig. 13.1. M
 atsushita RX-D30 stereo radio cassette player (1981) (1)The first double-cassette type

13.5

Creation of the “Headphone
Stereo”*

The Compact Cassette was rapidly improving in performanceand becoming established as the main tape recorder formusic. Users were building up collections of recorded
music at their disposal. Music appreciation was becoming
more personalised in style and individuals increasingly
had exclusive use of their own equipment. The idea of a“headphone stereo” clearly fulfilled people’s aspirations to“listen to music, anytime, anywhere” and would certainly
have a decisive effect on the audio environment of the
future. When these devices came out, some people viewed
the idea of a tape recorder that could not record as being
half-finished. However, the Compact Cassette tape recorder
had an acceptable level of performance and sound quality
and happened to serve the purpose of having “musicanytime, anywhere”. A tape recorder becoming the firstof these “headphone stereos” was clearly quite by chance,
and the concept of portable audio devices continued tochange and develop as advances were made in CDs, MDs,
semiconductors and media. The greatest success factor wasin the planning of a product that enabled people to “listen tomusic, anytime, anywhere”. The goal to achieve a portabledevice came down to the matter of making a simple machinethat was small, lightweight and low in energy consumption.
As there was a pre-defined tape size and mechanism for
the Compact Cassette, various mechanical innovations
and clever circuitry had to be incorporated into the tape“headphone stereo”, but developers finally managed toachieve the ultimate in downsizing.
*“Headphone stereos” refers to a general category of devices
perhaps better known by the pet name for the first model: the“Walkman”. The term is used without distinction in this report.

Fig. 13.2. Sony TPS-L2 (1979) The first Walkman (2)In 1989, Akio Morita, the chairman of Sony Corporation
at the time, wrote a thought-provoking passage in acommemorative publication celebrating the Walkman’s
tenth anniversary, outlining what sparked the creation of the
Walkman, the planning behind it, the naming of it and othermatters. The passage is reproduced below for reference.

R e p r i n t e d f r o m “ Wa l k m a n Te n - Ye a r A n n i v e r s a r y
Publication”, Sony Public Relations Office, ed. (1989)
Walkman a Success in Product Planning
Akio Morita, Chairman of Sony Corporation (at the time)
Was it 1978? One day, Mr. Ibuka came into my officecarrying a remodelled cassette player and a pair ofheadphones and said, “I wonder if you could listen to a stereo
while you’re walking.” At the time, stereos and headphones
were too big and heavy to listen to while walking. But when
I listened to the sound on Mr. Ibuka’s remodelled player,
there was definitely something better about it than listening
to music through a speaker. You could also listen to it by
yourself. I thought, “Well, this is quite fun!” After that, I
started thinking about where people listened to music. Youngpeople had stereos in their rooms, cars had car stereos—but
you couldn’t listen to music while walking down the street. I
thought of how I had seen people from time to time walking
along carrying a radio cassette player with them. “Youngpeople want to listen to music all the time,” I thought. I
started thinking with more interest about the cassette player
Mr. Ibuka had brought in to me.
Mr. Ibuka had also suggested remodelling the popular“Pressman” cassette recorder and taking out the recording
unit and speaker. I asked everybody, “Wouldn’t it be more
fun if we could make a stereo much lighter?” Most of themsaid, “That would never sell.” There was no support fromanyone in our acoustics division either. This was because “wehad never sold a tape recorder that could not record”. But
when I thought about it, we sold a lot of car stereos and they
could not record. So I thought, “All you need when you’re
walking is a player. Let’s definitely make one.” I got serious
and gave the order to build a prototype. Super-express
development got under way, with the strict aim of launching
it on 1 July 1979.
During that time, I was thinking, “We have to come up
with a good name for it.” One day, when I came back froma business trip, Mr. Kuroki, who was head of the Product
Planning Center at the time, told me, “We’ve decided on thename ‘Walkman’.” “Walkman? That’s an odd name. Aren’t
there any better names than that?” I asked. “Sorry, it’s toolate. All the packaging and posters say Walkman, so we can’tchange it. Please, will you accept it?” was his reply. “In thatcase, we can’t do anything about it,” I said. It went on saleon 1 July 1979 under the name of “Walkman” (TPS-L2). Of
course, at the time, we had no idea it would become sucha big business. I did, however, have some confidence andthought to myself, “We can do this.” This was because I
knew that young people could not do without their music.
Another reason was my own home situation: my children
were always pounding the stereo, but if they had this kind of
device, I could have some quiet in the house!
When we tried to market it overseas and took it to SONAM
Historical Development of Magnetic Recording and Tape Recorder253

(Sony Corporation of America), they said, “‘Walkman’ isweird – it’s not English. We’re not going to use that name.”
The name SONAM came up with was “Soundabout”. I
thought, “That’s a strange name, but we’re selling it inEnglish-speaking countries, so let’s go with what the people
in those countries say,” and decided to market it withthat name in the United States. But then Sony UK said,“‘Soundabout’ is no good!” The English have a certain pridein being the originators of their language and they were notsatisfied. So in England, the product was marketed as the“Stowaway”. I didn’t really know what this meant, either, butwhen in Rome, do as the Romans do.
However, the Walkman got very popular in Japan andvisitors from other countries would buy them to take homeas keepsakes. As this happened, the name “Walkman” started
becoming known overseas. The name was easily understoodby non-English-speaking people and use of the name started
spreading throughout the world. So I decided, “If that’s thecase, let’s just call it ‘Walkman’ everywhere in the world.” I
gave the presidential order (I don’t really like that word) tochange the name to “Walkman” in the United Kingdom andthe United States as well, uniting the “Walkman” across theworld.
The Walkman soon became a global hit and we put out newmodels one after another. The appearance of the Walkmanchanged the way people listened to music, which had a major
impact on the world. I know that when other companies laterput out their own stereos with headphones, everyone called
them Walkmans as well.
When I was awarded the Albert Medal by the United
Kingdom Royal Society of Arts in 1982, I said in my speechthat “although Sony has created various new products, weare actually not limited to manufacturing products. We alsoinnovate with words and have made ‘Walkman’ into an
English word.” I was given a standing ovation! But whatmade me happiest of all was when “Walkman” appeared in
the Oxford English Dictionary, the most authoritative English
dictionary in the world.
This means that “Walkman” has been recognised as an
English word. In the past ten years, we have given the world
50 million Walkmans, a new word and a way to listen tomusic that they didn’t have before. I think we can be very
proud of that.
The brilliance of the Walkman is in its product planning.
Cassette players and headphones already existed. However,what made the Walkman such a hit was the immense
creativity in the product planning. While new inventions anddiscoveries are important, the Walkman has proved that if wehave the sense to come up with a completely new productusing existing technology, it can develop into an entire
industry of its own.

254

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13.6

Advances in the Walkman

The first “headphone stereo” that appeared under the name of“Walkman” was a handheld TCM-100 recorder remodelled
into a playback machine. While opinions were divided as towhether it would sell or not, product developers adopted adesign that took full advantage of existing products to reduce
the risk. Since the same casing was used, the design wasalmost exactly the same in outward appearance as existingmodels, except for the blue exterior, which drew attention
to the device’s new image. The accompanying headphones
were a new, small, lightweight type that had been developed
and commercialised at the same time. Marketed this way,
there was overwhelming support for the product and it
became wildly popular in no time. With the huge success of
the TPS-L2, planning immediately started on new dedicatedplayback models, aimed at coming up with an original designthat would fully embody the “headphone stereo” concept.
When the Walkman came out in 1979, the market forstandalone, small-scale tape recorders was smaller than theradio cassette player market; there had been no investment in
the development of dedicated personal devices, so existing
devices had to be used for design miniaturisation and design
support. In 1981, the second “Walkman” WM-2 (Fig. 13.3)
was launched. This monumental model was the first to be
designed exclusively as a Walkman, expressly embodying
the “headphone stereo” concept and showing the way of
the future. Competition then ensued between many othermanufacturers as well as Sony to develop a product that was“smaller, lighter and played for longer”. The “headphone
stereo” fundamentally changed the way people listened tomusic.

Fig. 13.3. Sony WM-2 (1981) (3)The first Walkman specificallydesigned as a “headphone stereo”

13.7

The challenge of miniaturisation

Once headphone stereos had gained popularity, fierce
competition ensued to further enhance what were the portabledevice's most appealing features: small size and light weight.
Since the tape size was already predetermined, the devices
could not be made any smaller than this. However, one goal
was to make a device that was the same size as the case thatthe tape was put into, but this size was absolutely impossible
to achieve using existing tape recorder designs. The greatest
obstacle to making a tape player the same size as a tape casewas the size of the motor and the battery. Sony’s challenge
was to make full use of the characteristic properties of a
dedicated playback machine to make the ultimate small-sizedmachine. Compact Cassettes had a difference in thickness
between the area into which the heads were inserted and thearea where the tape was wound. This difference was around
1.5mm on each side. The first idea was to put the motor
into this area, so an ultra-thin, dedicated brushless motor
was developed. The standard design had two AA batteries;
however, the developers made a detailed study of themagnetic circuit in the motor and other areas and perfecteda design that could operate on one AA battery. Of course,
this required a new amplifier design that could run on 1.5V.
Even though there was only one AA battery, it was no simple
task as to where to put it. This is where the design capitalisedon the characteristic properties of a dedicated playbackmachine: the solution was to store the battery where theerase head would have gone (Fig. 13.5). While this design
achieved the ultimate in downsizing, it meant the unit where

the head was mounted, including the battery compartment,
had to be pulled out in order to load a tape and some people
would have inevitably thought of the device as a bit of a
gimmick. However, the cassette-case-sized Walkman WM-20(Fig. 13.4) was launched in 1983, and made a huge impact
with its size. It was truly an epoch-making point in Walkman
miniaturisation history.
The ultimate miniaturisation challenge was to make theperfect cassette-case-sized machine, even though it was not
actually possible to make a machine the exact same size asa cassette case, as the mechanism protruded a little when inuse. The AA battery was a constant hurdle to downsizing, so
developers worked on a new, thin, rechargeable “gumstickbattery”. They also worked on other developments todownsize individual components, such as developing new,special-shaped heads that were smaller in size. The expansionof the “headphone stereo” market and the significant
development investment that was being put in meant that itwas economically worthwhile to work on these components.
This created a virtuous cycle in which developers actively
worked on new components, which in turn increased theappeal of the overall product. The WM-101 (Fig. 13.6) was
released in 1985. Loaded with these new components, it
truly was the size of a cassette case, marking the end of thesize competition (Figs. 13.7, 13.8). Progress continued on
the Walkman in various ways, such as improved function
and performance, increased variation in models and moreadvanced designs. For a long time, it remained the favourite
choice of portable audio device, while the cassette deck
remained the machine of choice for recording on Compact
Cassettes.

Fig. 13.4. Sony WM-20 (1983) (4)The first cassette-case-sized machine

Historical Development of Magnetic Recording and Tape Recorder255

Basic performance improvements continued on the cassettedeck and new technology standards were set and standardised
for it, meaning that it now could record to a very high level ofquality despite the strict specifications in place. Developers
had made good use of the characteristic nature of dedicatedplayback machines and focused their efforts on making the“headphone stereo” smaller, which added to its productappeal. Of course, the success of the “headphone stereo”
was undeniably the very concept itself, which fundamentallychanged the way people listened to music.

Fig. 13.6. Sony WM-101 (1985) (6)The first machine to have a gumstick battery

Fig. 13.5. WM-20 structure (5)Motor position
Battery position(Year)

Fig. 13.7. Changes in Walkman motor and battery positions (7)256National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

TPS-L2
340cm³

Machine miniaturisation(Volume ratio: where 1 is the volume of the TPS-L2)
WM-DD
73％

Volume (cm3)

WM-2

TPS-L2

52％

54％

WM-20

WM-10149％

WM-501

Weight (g)

75％

45％

WM701C
Machine weight reduction(Weight ratio: where 1 is the weight of the TPS-L2)
200(Year)

Fig. 13.8. Progress of making the Walkman smaller and more lightweight (8)13.8Production Innovation

Since the creation of the Walkman, many of the costs
involved making it smaller and more energy efficient aswell as improving its sound quality and other functions
and performance. This work and its strong product appeal
meant that it had remained relatively highly-priced. Whilethe high-performance, small-scale, sleekly-designed models
were well received in Japan, the structure of the overseas
market meant that cheaper machines would sell better, eventhough they were slightly bigger and had fewer features.
Accordingly, lower-priced machines, produced by latecomer
manufacturers, continued to occupy a large share of themarket. Around the mid-1980s, Sony decided to work on a
product that was competitively low-priced and launched its“P-Project”, aiming to create a Walkman after the mannerof disposable cameras (also called “throwaway cameras”),
which sold for ¥980.
In an all-out cost-cutting move, the company discarded its
existing system of assembling mechanisms and electronic
circuit units separately and then putting them together.
Instead, it devised a system of directly incorporating themechanism unit onto a printed circuit board and dispensing
with the mechanism chassis. This system was a success.
Other success factors were the use of a lot of plastic parts andthe fact that this system used around half the usual numberof parts. The company also achieved a more streamlined
assembly process, with a one-way automated assembly
design that involved four mechanisms being made on one
printed circuit board and then separated afterwards to create

the final product. This approximately halved the usual cost,
thereby boosting the line-up of low-priced products aimed at
the global market with these domestically-produced products.

Fig. 13.9. P-Project mechanism (9)References
1)

Provided by Panasonic Corporation2), 3), 4), 5), 6), 9) Provided by Sony Corporation7), 8) “Walkman Ten-Year Anniversary Publication”, Sony (Inc.),
1989.

Historical Development of Magnetic Recording and Tape Recorder257

14 Invention of Digital Audio Tape Recorders (DAT)
14.1

Dawn of Digital Audio

Major technological developments took place on the
Compact Cassette throughout the 1970s and 1980s and it
finally reached a point of completion as a magnetic recording
system that performed adequately for consumer use. The
appearance of the Walkman in 1979 rapidly boosted theusefulness of the Compact Cassette, making it a vital partof the establishment and development of a new genre ofaudio products: portable audio. At the same time, tangible
results were being seen in the development of practicalapplications for digital audio and it was considered a matterof course that Compact Cassette systems would also progress
to being digital. The digitalisation of audio started with thedevelopment of magnetic tape recording systems and theend result was the DAT (R-DAT for consumer use). The
development history of the DAT is very important to digitalaudio.
Research on the use of digital technology in recording
and playing back audio signals began in the late 1960s,
under Heitaro Nakajima at the NHK Technical ResearchLaboratories. This was around the same time as talk of FM
broadcasts coming to the end of the experimental stage andstarting in earnest. FM broadcasts were stereo capable, had
acceptable sound quality and were very appealing to amateur
music enthusiasts and audiophiles. However, there was stillroom for improvement, as the sound quality was not quite
perfect. The question of how to improve the sound quality of
FM broadcasts triggered the development of digital audio inJapan. Researchers started out first by reviewing the current
situation: completely reconsidering and reassessing every
element that went into FM broadcasting, from programmes
to transmitters and receivers. The transmission itself as
well as the master tape recorders used in the various partsof production, such as compiling and editing sound, clearlyaffected the overall performance. It was clear that improving
the performance of these master tape recorders was of utmost
importance to improve the quality of FM broadcasts. Fig.
14.1 shows the dynamic ranges at each stage from recording
to transmitting. Magnetic recorders, enclosed by a dotted
line, had the smallest dynamic range and therefore limited
the overall performance of the entire system. Despite the factthat the master tape recorders of the day all used analogue
recording, they were high-performance business machines
and many of them were highly praised for their sound quality,
even by famous recording studios. While various attempts
were made to improve the performance of these master tape258

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

recorders by improving the key components, such as theheads, or the hardware, such as the driving system, or varying
the optimum recording levels, this achieved little in the wayof improvements, which meant that nothing significant could
really be expected to be achieved.
Having clarified the limitations of the existing analogue
machines, it was necessary to somehow come up with acompletely different solution. A proposal was made in thelaboratory to try applying digital technology to audio. At
the time, digital technology was being used in computersand communication technology. When researchers applied it
to audio recording, they could see how it was theoreticallypossible for the expected performance to far outperform thatof the existing analogue machines. However, while the ideaof digital audio recording – storing the waveform of a signal
as a numerical value – was relatively simple, implementing
it in an actual machine was no simple matter. A vast amountof data had to be recorded in a far greater volume than foranalogue recording; this had to be recorded and played backat very high speeds. The existing analogue tape recorders
could not cope with such demands. To solve this issue, anidea was put forward to use a video tape recorder (VTR),
which was being developed for business use at the time.
VTRs were designed for recording video signals; they usedrotary head technology to record a greater volume of signals
at a higher speed than that of an audio tape recorder. The
first audio prototype was completed in 1967, incorporating
an A/D-D/A converter and a signal processing circuit into
the VTR mechanism (Fig. 14.2). While the prototype wasmono, the properties of the sound were sufficient to show
the great potential of digital audio. The development teamconcentrated on further improvements to put it to practicaluse, completing a second prototype that was capableof stereo. In May 1969, a general-audience playback
demonstration was held at a public event hosted by the NHK
Technical Research Institute (now NHK Science & TechnicalResearch Laboratories). The fresh sound and lack of noise
stunned many industry stakeholders and general listeners in
the audience. Incidentally, the demo music was an overturefrom the Rimsky-Korsakov opera The Golden Cockerel,
performed by the NHK Symphony Orchestra, a fitting songchoice to usher in the beginning of the digital audio era.
The demonstration of digital audio to the public was a huge
success, but there was no means of editing the sound. The
devices were still in their early stage and would be difficult
to downsize; they also had their own digital countermeasuresfor noise (largely because of inadequate error correction).
The machines were not yet perfected enough to be of any

Relay circuit

High frequency distortion 1%(modulation distortion 3%)

Transmitter
100% modulation
Limiting amplifier
Adjustment amplifier
Adjustment amplifier
Preamplifier output
Preamplifier input
Modulation distortion 1%

Standard adjustment level
Magnetic recorderHigh frequency distortion 3% level
Harmonic frequency distortion 3% level

Level regulation signal
Disc-style recorder

Maximum amplitude of 30 types of record
Average maximum amplitude of 30 types of record

Okay up to about 130?

Velocity
amplitude

Noise level (A curve)
Noise level (full bandwidth)

Equivalent soundpressure

Microphone
Equivalent noise level (A curve)
Equivalent noise level (full bandwidth)
StudioMaximum peak of 36 orchestra pieces
Average maximum peak of 36 orchestra pieces

Soundpressure

Noise level(full bandwidth)

Noise level (A curve)

Fig. 14.1. Assumed dynamic ranges of the entire FM broadcasting system (1)practical use as master tape recorders for broadcasting.
The NHK put the development of digital audio recorders
on hold for the time being, perhaps because it had deemedthat it would take vast resources to address the issues inquestion. However, Nippon Columbia, which had worked on
improving the sound quality of records by direct cutting, hada technical interest in digital audio and its potential. It took
over the research and development of the technology and wasable to create a master tape recorder with it. The machineused a so-called four-head VTR, with two-inch tape, as its
recorder, complete with a 47.25kHz sampling frequency and13-bit linear quantization. LP records that were mastered andproduced on this digital master tape recorder went on salein 1972 under the name of “PCM Records” (Fig. 14.3). The
superior sound quality was highly regarded and became all
the rage among audio enthusiasts.

Fig. 14.2. Digital audio recorder prototype 1 (2)Historical Development of Magnetic Recording and Tape Recorder259

Fig. 14.3. Japan’s first PCM record (1972)
Recorded on a digital recorder independently
developed by Nippon Columbia and used as amaster record
Competition over the Development of

14.2 Stationary-Head Machines for Business Use
Digital audio was unveiled for the first time in a publicdemonstration in 1969, taking major electrical manufacturers
by surprise at its tremendous potential. Inspired by thedevelopment of the digital audio tape recorder (DAT), major
electrical manufacturers hastened their development ofmaster tape recorders for business use in the early 1970s.
Production technology at recording studios and other music
production sites became more sophisticated, with multitrack recording and more complex mixing processes. Inturn, this required higher levels of sound quality with agreater dynamic range and higher S/N ratio than the existing
analogue equipment. The audio genre began to make rapid
progress as an industry; advanced recording and playbackequipment became essential to audio device manufacturers
for assessing and analysing their machines. Given thesedemands, fierce competition ensued to develop a DAT
for business use. Several fairly-perfected systems were
proposed right at the end of the 1970s (Table 14.1). Mostof the systems proposed at this time were “stationary-head”
machines, with open reel tape drive systems and heads withmultiple recording tracks on them. These were very similar
in appearance to the existing analogue master tape recorders.
Although a number of major Japanese manufacturers,
such as Sony, Mitsubishi, Hitachi and Matsushita, worked
on developing this technology together with NHK, it was
the BBC in the United Kingdom that developed and testbuilt a digital recorder with a stationary head like theordinary analogue machines around 1972 (Fig. 14.4). The
technology was taken over by US company 3M, which used
it in a 32-channel machine using one-inch tape and a fourchannel machine using half-inch tape. Production of thesemachines stopped after several years, due to their high260

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

price and propensity to break down. In 1977, US company
Soundstream remodelled the tape recorder, developing andannouncing a four-channel DAT, but this, too, failed to gain acommercial footing and disappeared within a few years.
While DATs started out using VTR rotary head mechanisms,
many stationary-head systems were developed because
they were thought to be more beneficial for multi-trackrecording and editing. Both manufacturers and producers
were rather conservative and felt uneasy with the rotary headmechanisms that had been developed for VTR and their easeof use; they already had certain underlying assumptions ofwhat tape recorders should be like. Table 14.1 shows thestationary-head digital tape recorder systems for business use
announced by each company. Compatibility required at least
a minimum level of collaboration; accordingly, discussions
were held at AES to define the Digital Audio Stationary
Head (DASH) format in 1983. In 1985, the Professional
Digital (PD) format was also proposed as a rival to DASH.
Before long, fierce competition spread throughout the worldof digital master tape recorders. Both systems had been
independently developed by Japanese manufacturers, and it isno overstatement to say that the technology was completely
Japanese and that Japan was leading the world in digital taperecorders for business use (Fig. 14.6). This accumulated
technology and success with new audio equipment, suchas the “headphone stereo”, the radio cassette player andthe small-scale stereo, were major factors behind Japanesemanufacturers leading the world in developing DATs for
consumer use.

Fig. 14.4. BBC stationary-head DAT prototype (1972) (3)Fig. 14.5. Sony 24-channel stationary-head DAT prototype (c. 1977) (4)Fig. 14.6. Sony PCM-3324 DASH format 24-channel DAT (5)Table 4.1. Comparison of Stationary-Head Prototypes for Business Use (6)
5

6

7

8

9

1977

1978

1978

1978

1978

MitsubishiSoundstreamMatsushitaSony

Mitsubishi

Toshiba

1/2

1/4

1

2

4

1/4
2

1/4
2

1/4

2

1/4
2

28

6.5

4.5

6

30

3.5

4

16

38

76

38

38

76

38

38

38

38

32

52

35.7

48

50

49.152

50

44.1

50

13

12

13

Biφ

12
MFM

15
MFM

14.7 curve

MFM
12

16
MFM

12.7 curve

MFM
5.55

3.3

17.9

2-bit parity
Double winding

Adjacent
code

17.64
CRCC
adjacent
code

3.3
1-bit parity
Previous
value holdNo.
Year announced

1

2

3

1972

1974

1975

4
1976

Announced by

BBC

Sony

HitachiTape width (inches)
No. of channels
No. of tracks(per channel)
Tape speed (cm/s)

1/2
2

2
2

8

Sampling frequency(kHz)
Quantisation (bit)Modulation method

MFM

13
NRZ

Linear recording density (kbpi)

4.4

1.73

Error control

2-bit parity

ParityCRC
Doublewinding interpolation correction

2

Biφ

Historical Development of Magnetic Recording and Tape Recorder

261

14.3

PCM Processor Concept

Many stationary-head DATs for business use were introduced
as vital pieces of equipment to recording studios and othermusic production sites. The Sony DASH machines and
Mitsubishi PD machines were competing for the market andquickly replaced the analogue master recorders and multichannel tape recorders from the West that had dominatedthe field of business-use recorders. The following are themain reasons why Japan became a major power in the age ofdigitalisation.
- There were many parts manufacturers with precision
machining technology able to develop and supply thehigh-precision, specialised components needed forbuilding advanced tape running systems- S uperior head processing/assembling technology
to incorporate multiple narrow track cores onto asingle head (including thin films heads made withsemiconductor manufacturing technology, etc.)- Technology to develop and manufacture superior
magnetic substance and tape suitable for digital recording- Technology to develop and manufacture high-density,
high-performance, dedicated semiconductors (signal
processing, AD/DA converters, microprocessor control,
servo LSI, etc.)- Studies on the logical aspects of signal processing, suchas error correction and modulation method, and rapid
adaptation to hardware- H igh precision general electronic components andmechanical parts
Tape recorders became increasingly digitalised throughout
the world of business machines; by the mid-1980s, studios
and broadcasters throughout the world had replaced theirmachines en mass. There were also growing opportunities
for consumers to experience digital audio sound. While
appreciation for digital audio steadily grew among music
lovers, developing the technology for consumer use wasconsidered too difficult. DATs for business use were far more
expensive than the existing analogue machines, requiring
far more parts. Being open-reel machines, they were also
lagging behind other consumer-use machines in terms of
their user-friendliness. There was no real expectation thatthey would ever become popular-use machines. Despite
having developed stationary-head machines for business use
and gained major footholds in the business market with their
DASH and PD formats, even Sony and Matsushita struggled
to develop a machine for consumer use.
At the same time, VTR for home use was entering its final
stage of development. “Betamax” was announced andreleased in 1975, followed by “VHS” the following year in
1976. Home-use VTR made its debut with high hopes of262

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

making it big. Machines capable of recording 1-2 hour TV
programmes entered the market at affordable prices. These
were superior products with much thought put into their userfriendliness, such as having a relatively small cartridge sizewith half-inch tape. Admittedly, earlier VTR cartridges had
been seen, in the form of the “U-matic” cartridge in 1971.
At ¾-inch, the tape in these machines was wider than in the
Betamax and VHS machines. This meant that the cartridges
and machines were larger and more expensive, so they did
not become popular for home use. Nevertheless, they began
to be used by businesses such as broadcasters and came toplay a leading role in Electronic News Gathering (ENG).
The team at Sony’s research and technology division began
to wonder whether a digital audio recorder could be madeusing a household VTR as a recorder. The first DAT trialledby the NHK was a business-use VTR; while it was not theusual use for the VTR mechanism, with a little effort the
VTR itself could be made to record a digital signal. While
the price of household VTRs was expected to eventually go
down, the necessary alterations to make them into dedicatedDATs meant that there would probably be no cost benefits
to mass production. Development promptly began on astandalone digital audio circuit, with the idea that if such amachine could be simply used as a recorder without touching
the VTR technology, the result would be a household DATthat was affordable to general users. Since the purpose ofVTRs was to record television signals, they had horizontal
and vertical blanking intervals; this meant that they were inprinciple not really suited to recording continuous signals
such as audio signals. Digital audio involves treating an
audio signal as data, meaning that compression/expansion
occurs relatively freely on the time axis. In practice, however,it was more difficult than expected due to digital dataprocessing taking up a lot of memory and costing more than
anticipated. Furthermore, the idea of error correction had notbeen thought through. Dropout (signal loss) on a VTR has
no major effect on the picture, but it produces a catastrophic
amount of noise. However, although the latest digitaltechnology was still lacking in many areas, Sony released
the consumer-use PCM processor in 1977, which worked
directly connected to a VTR, kicking off the popularisationof digital audio machines for general users (Fig. 14.7).

Fig. 14.7. The world’s first PCM processor, Sony PCM-1(¥480,000) (1977) (7)14.4

Creation of Consumer-Use DATs

Digital recording had been limited to the world of business,but the advent of the PCM processor meant that it could
now be enjoyed in the home as well. As general users cameinto increasingly more frequent contact with digital audiowith this machine, its sound quality began to receive more
attention in publications such as audio magazines. Thisearned recognition of digital audio as something with appeal
and potential, and raised expectations regarding it. Aroundthe same time, the audio world was ablaze with news ofdevelopments and format disputes in relation to digital audio
discs, which later led to the Compact Disc. As expectations
regarding digital audio grew, naturally, so did the idea
to digitalise the Compact Cassette, the leading magnetic
recording system for consumers. In fact, as the CD was being
developed, audio companies were researching digital taperecorders for consumer use; however, by the early 1980s,
none of them had made it any further than the laboratory
stage. Even amidst this race to develop a digital tape recorderfor consumer use, competition was raging between thestationary-head (S-DAT) format, which focused on the audio
aspect, and the rotating-head (R-DAT) format, which aimed
to improve on the existing VTR technology (Figs. 14.8,14.9).
The CD – a digital version of the existing analogue records– entered the market in 1982 and immediately took hold as amusic storage medium. CDs and CD players were a systemwith overall appeal that not only offered good sound quality,
but also a novel shape, superior digital operability using TOC
data and the convenience of random access. The successful
introduction of the CD intensified the race to develop digitalrecorders for consumer use. The term “DAT (Digital Audio
Tape-recorder)” seems to have taken hold around this time torefer to digital audio tape recorders for consumer use.
Developers thought up ideas to combine the far superiorsound quality of digital audio with an extra recording area for
additional information, called sub-code, to vastly improve theuser-friendliness of the DAT. This led to the proposal of new,highly-advanced, highly-desirable specifications. In termsof performance, the DAT outdid the CD with a sampling
frequency of 48kHz and 16bit quantisation. It also offered
two hours of continuous recording on a cartridge smaller
than the Compact Cassette – it truly was a dream machine.
However, companies worked on it separately, meaning alarge number of incompatible formats, which prevented itfrom becoming popular. A major factor to the success of theCompact Cassette was maintaining strict compatibility; allcompanies involved understood the importance of having
unified standards. Accordingly, the industry organised
a “DAT Discussion Panel” in 1983 to work on unifying
standards. A comparison was made between the R-DAT and
S-DAT formats and uniform standards were formulated forboth formats. Around two years later, in 1985, technicalspecifications were issued (Tables 14.2, 14.3) for S-DAT and
R-DAT, based on the results of various investigations andexperiments. Having compared the two formats, a comment
was passed acknowledging the advantage of R-DAT in termsof short-term implementation. Consequently, R-DAT was
first commercialised as a DAT for consumer use (Figs. 14.10,
14.11). The following section discusses the development ofeach DAT format for consumer use.

Fig. 14.8. Sony S-DAT prototype (1981) (8)Fig. 14.9. Sony R-DAT prototype (1982) (9)Historical Development of Magnetic Recording and Tape Recorder263

Table 14.2. Main S-DAT Specifications (10)Recording/Playback Mode

Mode

Standard

Option 1

Option 2

Option 3

Pre-recorded(1) No. of channels

2

2

2

2ｘ2

2

(2) Sampling frequency (kHz)

48

32

32

32

44.1

(3) Quantisation (bit)

16

16

12

12

16

(4) No. of data tracks

20

20

20

10ｘ2

20

(5) Tape speed (cm/s)

4.76

3.17

2.38

4.76

4.37

(6) Transfer rate (MBPS)

2.4

1.6

1.2

1.2x2

2.205

(7) Linear recording density (kBPI)

64
double Reed-Solomon code
C2: (29, 27, 3) C1: (40, 32, 9)(8) Error correction code

8-10R(9) Modulation method(10) Redundancy (%)36(11) Sub-code rate (kBPS)

128

85.3

64

64x2

117.6

(12) ID code rate (kBTS)

10

6.66

5

5x2

9.19

90

98

(13) Cassette dimensions (mm)86x55.5x9.5(14) Maximum recording
time (minutes)(tape thickness 10μm)

90

135

180

Table 14.3. Main R-DAT Specifications (11)Mode
No. of channels (CH)Sampling frequency (kHz)
Quantisation (bit)Linear recording density (kbpi)
Areal recording density (Mbpi2)

Transfer rate (Mbps)
Sub-code capacity (kbps)

Recording/Playback Mode
Option 2
Option 1(32k-4 CH mode)(32k mode)Standard(48k mode）
2

2

48

32

16 (linear)

16 (linear)

61
114
2.46

2.46

273.1

273.1

2
32
12 (non-linear)

Modulation method
Correction method
Tracking method

Tape thickness (μ)
Tape speed (mm/s)

32

44.1
16 (linear)

61

61

61.1

114
1.23

114

12 (non-linear)

76

2.46

2.46

136.5
273.1
8-10 modulation method273.1

double Reed-Solomon code
Area split ATF
73x54x10.5
120

120

240

120

120

80

3.81
Metal powder

Oxide tape
13±1μ

8.15

8.15

Track pitch (μ)
Track angle

8.15

4.075

8.15

12.22513.591

13.59120.41

6° 22'59.5''
φ30, contact angle 90°

Standard drum specifications

Drum rotation speed (r.p.m.)
Relative speed (m/s)
Head azimuth angle
Notes

Dedicated Playback Mode
Wide track
Normal Track(44k-WT mode)(44k mode)22
16 (linear)

Cassette size (mm)Recording time (minutes)
Tape width (mm)Tape type

Option 3(32k-4 CH mode)
4

2000

1000

3.133

1.567

2000
3.133
±20°

Always equippedwith standard
recording mode

Option for PCM
broadcast recording

Half-speed option
for long recordings

4ch option

6° 23'29.4''
2000
3.133

3.129

Always equipped with dedicated Always equipped with dedicatedmusic tape mode
music tape mode
Playback only;
Playback only;
suitable for contact printing
cannot record

Fig. 14.10. Sony DTC-1000ES, the first R-DAT machine (1987)

Fig. 14.11. Portable R-DAT Sony TCD-D3

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Confident in its accumulation of tape recorder technology,Sony’s research and technology division set about
researching and developing a consumer-use DAT in earnest
in the late 1970s. At the time, the question of what
technology could be used to achieve a consumer-use DAT
was a topic of heated debate among audio engineers. There
was no obvious answer, which in itself often let to sharply
opposing views among engineers. There were several
opposing groups of engineers at Sony, each advocating its
own opinion. The path Sony took was to have these groups
develop three separate formats concurrently.

14.5.1 Stationary Heads
This was the archetype for the S-DAT format, based on thesame tape running system as the existing cassettes. This head
could record multiple tracks at once, meaning it was capableof handling the necessary volume of data. The main aim of
this development was to produce an ultra-precise recording/playback head capable of recording around 20 tracks per
side with a 3.8mm tape like the Compact Cassette. To readan accurate signal from the countless number of narrow
tracks, the playback head used the magnetoresistance (MR)effect. Developers worked on an MR head that could read thechanges in magnetism on the tape as changes in resistancein the MR element. Both the playback head and recording
head utilised a new innovation called the “thin film head”,
made with semiconductor processing technology. This
manufacturing process was later used to create multichannel
DAT heads for business use. Fig. 14.12. shows the S-DAT
track pattern.
Philips later developed the S-DAT idea into the Digital
Compact Cassette (DCC) system. Since the S-DAT system
had 20 tracks for the main audio data, it required a very
precise tape running system and advanced signal processing.
The DCC system had less than half the number of tracks,
allowing the heads and the overall system to be simplified.
Any performance limitations due to the reduced

recording density could be compensated for with “datacompression technology”. This was a second-generation
DAT with sound quality rivalling that of the CD. The
cassettes were also compatible with the Compact Cassette
system and there was a standard in place to ensure that a
DCC machine could record and play DCCs as well as play
Compact Cassettes. However, the DCC lost out to the MD
and disappeared off the market within a short space of time
(Fig. 14.13).

Tape
Tapeline
centrecentre line

Format Competition in Developing
DATs for Consumer Use

Tape
Tape edge
line

14.5

Fig. 14.12. S-DAT track pattern (12)Recording

Playback

Digitalrecording/playback
Analogue playback

Fig. 14.13. DCC track pattern (13)14.5.2 Rotary Heads
The so-called R-DAT format was used by a minority ofcompanies in the industry who hoped to produce a consumeruse DAT with this format. The key part in the rotary headsystem was the rotary drum, which included the heads. Thisrequired redeveloping the entire system from scratch. It wasa major hurdle for manufacturers to develop a dedicatedHistorical Development of Magnetic Recording and Tape Recorder265mechanism when they had only ever built the existing styleof tape recorders and had never worked with a helical scantape drive system. Generally, it takes time to develop a newmechanism, building up experience and testing prototypes.
There was much more involved in this development than forthe stationary head, which only required remodelling existingparts to make them smaller and concentrating on producing
a multi-channel head. Sony was working on an 8mm
video around the same time and pushed forward with DATdevelopment in this format. It was fairly straightforward
for the audio engineers to learn and use the unfamiliar
rotary head technology, such as the various components
and the tape drive technology. The developers worked
on a dedicated audio mechanism using VTR rotary headtechnology, taking care to simplify and downsize it to makeit more appealing (Fig. 14.14). By making maximum use ofexisting technology, they were able to keep the development
reliable and rational. The R-DAT system became asignificant piece of recording equipment in its day. It had
good functionality and performance and reached an adequatelevel of completeness as a consumer product quite early on,
becoming recognised as the first DAT for consumer use. It
was made into a series of products: decks, portable machines
and professional equipment, and was sold all over the world.

Fig. 14.14. R-DAT mechanism
Drum diameter: 30mm
Winding angle: 90º
No. of heads: 2
No. of motors: 4

14.5.3 NT Format
The stationary-head S-DAT prototype (Fig.14.8) wasannounced in 1981, followed by the rotary-head R-DAT
prototype (Fig. 14.9) in 1982. These formats continued
to develop and were put up for examination at the “DAT
Discussion Panel” with the aim of standardisation. Whilethese developments in the digitalisation of the Compact
Cassette continued, Sony’s research and technology division

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was working on another DAT format. The aim of this design
was not just the minimum necessary development to improvesound quality through digitalisation, but rather to create an
ambitious new product that used digitalisation technology to
its maximum potential to achieve a level of miniaturisation
thought impossible in a tape recorder, thus creating newvalue in the product. The product was the NT system, witha sampling frequency of 32kHz and 12-bit quantisation,
capable of two hours of digital recording on an ultra-smallcassette the size of a postage stamp. It was launched in 1992
as the “NT-1”. Housed in a tiny casing and powered by asingle AA battery, the device was packed with a mechanism
as small and precise as a watch as well as a circuit forevery function from recording to playback to digital signal
processing. The small size of the specially-developed tape
was astounding; it even appeared in the 1994 Guinness Book
of World Records as “the world’s smallest mass-producedtape” (Fig. 14.15).
The mechanism developed for this machine made full use of
the distinct nature of digital data with a non-tracking rotaryhead system that traced the signal-recorded area (track)
multiple times, reading only the necessary information
without fully tracing the entire track. The mechanism thenre-aligned this digital data along the time axis, producing
the correct signal. The product name “NT” was an acronym
for “Non-Tracking”. The ultra-small cassette itself had anumber of clever ideas incorporated into it. The device also
had a non-loading mechanism, whereby the drum on which
the rotary heads were mounted was inserted into the cassette.
The mechanism had to be miniaturised to achieve this (Fig.
14.16). With low electricity consumption in its electronic
circuits as one of its goals, it offered astounding performanceby running on a single AA battery. While this was a very
technically ambitious development that fully incorporated
digital technology and mechatronics, it did not succeed as abusiness venture. This was perhaps because the greater thedetail, the more time it took to develop. It was released in
1992, the same year as the MiniDisc (MD); this was the eraof second-generation digital recording systems using digitalcompression technology. The MD made full use of thiscompression technology and showed great promise for the
future. This provided a good opportunity to get a number ofinterested parties thinking about the possibilities in switching
to semiconductor memory recording media, which was stillquite expensive at the time.

Fig. 14.15. Sony NT-1 and exclusive tape (1992) (14)Tape guideRollerTape running
direction

RollerTape guide

Tape

CapstanDrum

Fig. 14.16. Non-loading mechanism (15)

14.6

Copyright Issues

Given its overwhelming recording and playback capabilities,
the appearance of the consumer-use DAT was an epochmaking event in tape recorder history. The nature ofdigital recording meant that the content would not become
corrupted through copying, which sparked a debate overso-called digital copyright issues. In 1987, CD shipments
were outselling analogue records; CDs had become a major
revenue source for the record industry. The appearanceof the DAT, which could record CDs without losing any
sound quality, inevitably presented a major threat to thosewith financial interests in the music content. Althoughtape recorders had typically been used up until that time
to copy records onto Compact Cassette and listen to themon “headphone stereos” or car stereos, the establishedinterpretation of music copyright in Japan allowed private
recordings to be made for use within the household. A
decision by the Supreme Court of the United States in theso-called “Betamax case” in 1984 held that home use of a
VTR does not constitute copyright infringement. Rather
than permitting copying, the decision interprets that it islawful for consumers to use a VTR as technology that offersa time-shift function. Music/video copyright holders were
becoming increasingly nervous about the growing spread ofmachines capable of making copies. Hardware developers
for consumer-use DATs had given this matter someconsideration; the first machine released had its specifications
set in such a way that it could not digitally record at 44.1kHz,
the sampling frequency of CDs. However, this created a
discord between those creating the content and those creating
the hardware. It was difficult to dispel users’ doubts andmisgivings, thus tripping the DAT up in its initial sprint.
The hardware and content factions entered into a number ofnegotiations over what was arguably the world’s first digital
copyright issue; by 1990 they had reached an agreement. The
two essentials of the agreement were as follows.
(1) Serial Copy Management System (SCMS) technologythat restricts copying shall be used when making digitalcopies, preventing unlimited copies being made.
(2) Each country shall develop legislation to apply a private
copying levy system to digital recording equipment andmedia (such as tape).
Rather than determining whether a single copy wasprohibited/permitted, the SCMS prohibited/permitted
copies according to the source of the recording. The systemdetermined whether or not a digital copy was prohibited/
permitted according to what the original source of a digital
copy was. This meant that first-generation protected works(such as CDs) could be copied, but following generations
could not be copied. The goal of this was to prevent a floodof “copied works of the same quality as the original”, which
was one of the advantages of digital recording. This was acompromise to uphold consumers’ right to private copying aswell as alleviate the threat digital copying posed to copyrightholders. Combining this system with a private copying levy
system resulted in agreement over the first digital copyrightissue in history.
Around the time that CDs were announced, Sony andPhilips came up with a unified standard for transferring
data between digital audio machines. This was called theSony Philips Digital Interface (SP-DIF) and was used inbusiness machines. After CDs hit the market, the standard
was developed into the international standard IEC958 (now
IEC60958) for consumer use. Specific SCMS information
was transmitted along with audio data according to standard
IEC958; this additional information included information
pertaining to the generation of the content (music) being
played. The information also determined the source machine
and the destination machine and distinguished what kindof machine the digital data came from. This information
determined the behaviour of the recorder receiving thedigital data. Tape recorders could of course record noncopyrighted works. Material recorded privately by users withno copyright claims to it could be freely digitally transferredHistorical Development of Magnetic Recording and Tape Recorder267

and copied on SCMS machines. This agreement allowed
digital copying from first-generation CDs only. In 1990, theDAT re-emerged as an SCMS-compatible device and waswelcomed as the ultimate tape recorder by audiophiles, semiprofessionals and even fully-fledged professionals. Later,
second-generation digital recorders for MD, DCC and othermedia, aimed at a wider range of users, also started using thissystem that had been established for the DAT. The transition
to SCMS was relatively smooth and a definite market forthese recorders developed within a short space of time.
The digital copyright debate started with the emergence of
the DAT. The debate continued as computer technology anddigital video technology (DVD, BD) advanced, with theprotection and use of digital content becoming a major topic
of concern.

References
1)Mori, Yoshihisa, et. al. Onkyō-Gijutsu-Shi [History ofSound Recording], Tokyo University of the Arts Press,
March 2011, p. 143.

2)

Ibid., p. 144.

3)

Ibid., p. 145.

4)

Onkyō-Gijutsu-Shi, p. 145.

5), 7) 14) Provided by Sony Corporation.
6)

Onkyō-Gijutsu-Shi, p. 146.

8), 9) Ibid., p. 148.
10) Ibid., p. 149.
11) Ibid., p. 150.
12) Ibid., p. 152.
13) Ibid., p. 153.
15) Ibid., p. 154.

268

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Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

15 Conclusion
The most common style in which people listen to music today
is of listening to music stored in a semiconductor memory
on a small-scale, portable device through headphones.
Small-scale, battery-operated devices enable people tolisten to music while on the move, at a destination point, or
individually at home through headphones. Making music
personally accessible anytime, anywhere is quite a recent
achievement that only became possible around 30 years ago
with the appearance of the portable “headphone stereo”. The“Walkman” at that time was a dedicated playback tape playerthat used the very successful Compact Cassette format. Thishistoric product revolutionised the style in which people
listened to music and took hold with a culture of its own.
Music listening developed as a means of household
entertainment as technology developed in the 20th century.
Related equipment and service industries were also very
successful. It was not all that long after sound was firstrecorded on Edison’s phonograph that listening to music
recordings on disc-style records became a popular style ofenjoying music at home. As the record industry rose to theforefront of the times, there was a flurry of development to
try to improve the sound quality of recording and playbackmachines. As electrical technology advanced, researchcontinued on the disc-style records to improve their soundquality and lengthen their playing time. This work reachedcompletion in the late 1950s with the stereo LP record, whichthen came to play a long leading role in home audio.
The theory behind the gramophone (record) was that ofrecording sound on mechanically etched grooves in themedium. The idea of “magnetic recording”, wherein soundchanges are captured as electrical changes and recorded
as changes in induced magnetism, had been proposed
and the steel wire magnetic recorder invented at the endof the 19th century. Magnetic recording developed in theform of the tape recorder in Germany prior to the Second
World War. Following the war, the United States and othercountries worked tireless on technology development,
resulting in a superior recording machine, as discussed
in Chapters 3 and 4 of this report. Research on magnetic
recording was carried out in Japan quite early on as well,with results rivalling those of other countries, such as thediscovery of AC bias and the development of new magnetic
substances. Undoubtedly, this research and the accumulationof technology laid the foundation for developing thedomestically-produced tape recorder into a major post-war
industry. The Compact Cassette appeared in the mid-1960s
and started on its journey towards becoming the de facto
standard. The Compact Cassette performed poorly alongside
the open-reel machines of the time and was thought to beunsuitable for music recording, one of the main purposes
for recorders. Various Japanese manufacturers worked hard
to solve this issue, developing new magnetic substances
for the tape, new head materials, more precise mechanism
designs, smaller motors for sound applications and improved
technology for rotation control. These developments
culminated in the cassette deck, proving that the Compact
Cassette could perform satisfactorily as a music recorder andboosting the confidence of users and manufacturers alikein the potential of the Compact Cassette. While adhering tostandards that emphasised compatibility in some respects
prevented any short-lived innovations, working on precisedevelopments in limited conditions to achieve superior
function and performance perhaps suited the Japanese styleof product development. Japanese manufacturers, brimmingwith confidence at having made major contributions to thedevelopment of the Compact Cassette, were competentenough to draft new standards and even formulated their own
standards for the Microcassette and Elcaset in the 1970s.
Japanese-made music equipment had its beginnings in thetransistor radio. By the early 1970s, it had become a major
export industry, with Japan sending out audio equipment far
and wide on the global market. Manufacturers of mechanicaland electrical components for the Compact Cassette taperecorder developed their technical capabilities, which boosted
the potential for the product. The pace of product planningand development quickened, aimed at expanding the rangeof possible uses for the tape recorder by making it smaller
and lighter. As the idea of portable audio made possible
by a smaller and lighter product began to take hold, thedevelopment of integrated products such as the radio cassette
player enabled users to build up their music collections on
Compact Cassette. It was in these circumstances that the
Walkman was created: a product designed to enable people
to “listen to music, anytime, anywhere”. Although the
Walkman was a type of tape recorder, the essential point
was the concept of “listening to music, anytime, anywhere”.
Other products using other media, such as CDs or MDs, werealso developed along the same concept and continued to be
popular. According to a report by Sony, it had shipped out acumulative total of 220 million personal tape players and 120
million personal CD players by 2009.
By expanding the range of uses for Compact Cassettemachines, Japan began to lead the world in tape recordertechnology and products. As the age of digitalisation
approached, Japan was in a position to spearhead thedevelopment of technology and determining of policies.
While digital audio technology, with its ground-breaking
sound quality capabilities, radically altered the face ofHistorical Development of Magnetic Recording and Tape Recorder269

audio products, it was tape recorders that paved the way
for digitalisation. Business-use tape recorders improved
dramatically in performance; these were used for recording
high-quality master copies of music content. This contributed
greatly to the creation and development of the CD. Chapter
14 recounts the history of development of the Digital
Audio Tape-recorder (DAT). The consumer-use DAT was
the ultimate tape recorder system, achieving a level of
performance that had not been possible in the analogue era
on a cartridge smaller than the Compact Cassette. This was
the result of a winning combination between Japan’s precise
mechatronics and semiconductor technology and its ability
to develop basic components, such as tape heads – a skill
learned and refined during the competitive development ofCompact Cassette machines. Digital audio afforded a greater
degree of freedom in signal processing than analogue. The
compression process meant a reduced volume of media; it
was also possible to transfer music data without the use ofstorage media. The beginning of the chapter mentions thatthe modern style of listening to music came about throughthe development of digital technology. While the role of thetape recorder has been taken over by recording devices withhard disks or semiconductor memory, in terms of the way
in which music is appreciated, there has been no change
in the basic concept embodied in the Walkman. Just as theCompact Cassette “headphone stereo” revolutionised the way
in which people listened to music, the hope is that Japan’s
development and product planning capabilities will transform
digital audio with a new breakthrough that will offer users
unexpected, new experiences and enjoyment.

Acknowledgements
The author received invaluable materials and informationfrom many sources when preparing this “Systematic
Examination of Tape Recorder Technology” report.
The author is very grateful for having been able to ask
contributors for more detailed descriptions and accounts andexpresses his heartfelt gratitude to the following people inparticular.
Yoshiharu Abe, formerly of TEAC Corporation
Masahiro Fujimoto, formerly of JVC
Mitsuru Kashiwabara and Sadaharu Igeta, of Sony
Corporation
Satoshi Kageyama and Noriaki Furuta, formerly ofPanasonic Corporation
Masanori Harui, of Panasonic Corporation
Masami Murayama, of Nissei Technology Corporation
Satoshi Shitara and Reiko Kinoshita, of JEITA
Ryoji Menjo and Yoshihisa Mori, of the Japan Audio
Society270

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

Cited Works* O ther than the literature cited in the “References”
section at the end of each chapter.
1) Nakagawa, Yakuzō. Dokyumento Nihon no Jiki
Kiroku Kaihatsu [Documented Japanese Developments
in Magnetic Recording], Diamond, 26 January 1984.
2)

Nakajima, Heitarō and Odaka, Kentarō. Zukai DAT
Dokuhon [Illustrated DAT Reader], 25 July 1988.

3)

Sekai no Ōdio: Tekunikusu [World Audio: Technics],
Stereo Sound Publishing, 20 May 1978.

4)

Sekai no Ōdio: Sonī [World Audio: Sony], Stereo
Sound Publishing, 31 October 1978.

5)

Ya s h i m a , K ō k i . S o n y C h r o n i c l e 2 0 1 0 , S o n yMagazines, 10 March 2010.

6)

Sony ES Review© Rinji Zōkan-gō (ES Review Sonī
Sōritsu 35 Shūnenkinen-gō) Audio 35 Years [Sony ES
Review © Special Issue (35 Year Anniversary Issue)
Audio 35 Years], Sony Corporation.

Historical Development of Magnetic Recording and Tape Recorder

271

1990

Steel wire/ribbon

Recording/playback heads

Recording media

DC bias1898 Poulsen Inventionof the Telegraphone

SecondWorld War

Ring heads

Iron oxide tapeAC bias1935 AEG Releaseof the Magnetophon

1928 Pfleumer Proposal of atape-style magnetic recorder

Creation of
the tape recorder1888 Oberlin Smith Conceptof magnetic recording published1940

1931 Blumlein Inventionof the stereo record

1930

1925 Bell Laboratories Inventionof electrical recording

Magnetic Recording in its Infancy
Creation of the wire recorder1887 Berliner Invention of
the disc-style Gramophone1877 Edison Invention of
the cylinder-style Phonograph1857 Scott deMartinville Inventionof the PhonautographTape Recorder Flow Chart

Gramophones and Records

Magnetic Recorders

Progress in component technology

StereoNAB
standardisation

1979 SONY Releaseof the Walkman

1977 Release of the PCM
processor for consumer use

Creation of
the Walkman

1982 Releaseof the CD

1980

Dolby B NR

Compact Cassette
standard 1962

Three standalone heads

Ferrite heads

1987 Release of R-DAT

Digital audio era

1992 Releaseof the MD

1990

Three heads
using combinations

Sendust heads

Metal tape

Evaporated tape

Dolby C NR

Small brushless
DD motors

Chrome tape

DC servos

Improved performance of cassette decks

Downsizing of portable cassette machines1962 Philips Releaseof the Compact CassetteAppearance and developmentof the Compact Cassette

Permalloy heads

Essential technology forthe modern tape recorder1970

1958 RCA Victor Releaseof the stereo record

1960

1950 Totsuko Release of the Gmodel, the first domesticallyproduced machine1948 Ampex Release of the
Ampex 200 for business use

Popularisation of
open-reel machines1949 RCA Victor
Release of the EP
record1948 Columbia Releaseof the LP record

1950

Timeline

Year

Event related tape recorders

Event related to recording/broadcasting

1857

Scott de Martinville invents the “Phonautograph”,
the world’s first sound recorder1877

Thomas Edison invents the “Phonograph”, theworld’s first cylinder-style recorder

1887

Emil Berliner invents the “Gramophone”, a discstyle recorder1888 Oberlin Smith publishes the idea of magnetic recording
1898

Valdemar Poulsen invents the “Telegraphone”, the world’s firstmagnetic recorder1902 Poulsen and Pedersen apply for a patent for DC bias
1920

Commercial radio broadcasts begin in the United States

1921 Carlson and Carpenter apply for a (US) patent for AC bias
1925

Radio broadcasts begin in Japan

Fritz Pfleumer completes the “Sound Paper Machine”, a tape1928
style recorder1934 AEG completes the “Magnetophon”
1938

Nagai, Igarashi and Ishikawa apply for the “Nagai Patent”, a(Japanese) patent for AC bias

1939 Wooldridge applies for a (US) patent for AC bias
1940 Weber and von Braunmühl apply for a (German) patent for AC bias
1941 Camras applies for the “Camras Patent”, a (US) patent for AC bias
1948 Ampex releases the Ampex 200
1950

Columbia announces LP records

Totsuko releases the G model, Japan’s first
domestically-produced tape recorder1951 Totsuko completes the M-1, a portable tape recorder1958 RCA Victor releases the RCA Cartridge system

RCA Victor releases the 45/45 stereo record

1962 Philips test-releases the Compact Cassette
1963 Grundig, Telefunken and Blaupunkt release the DC International format
1965

Philips EL-3301 becomes the first Compact Cassette machine
to be released in Japan

1969

Proper FM broadcasting begins in Japan

1970 BASF releases chrome tape1970

Matsushita releases the RS-275U, the first direct-drive cassette
deck

1971

TEAC releases the A-350, the first cassette deck with inbuilt
Dolby NR1973

Nakamichi releases the Nakamichi 1000, a three-head cassettedeck

1973 Sony releases double-coated DUAD tape1973 Sony releases the TC-2850D “Cassette Densuke”
1975

Consumer-use VTR “Betamax” appears

1976

Consumer-use VTR “VHS” appears

1977 Sony releases the PCM-1, the world’s first consumer-use PCM processor
1978 3M

releases Metafine metal tape1978 Matsushita releases Ångrom evaporated tape for microcassette
1979 Sony releases the TPS-L2, the first Walkman
1982
1983 Cassette-case-sized Walkman WM-20 released
1987

Consumer-use DATs appear

1992

272

Compact Discs (CDs) appear

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

MiniDiscs (MDs) appear

Historical Development of Magnetic Recording and Tape Recorder273

Reason for Selection

1968
1963
1977
1973
1970
1976

TC-50, a handheldCompact Cassette recorder

RQ-303 MySonic, a small-scale,battery-operated, open-reel tape recorder

PCM-1, the world’s first PCM
processor for consumer use“Cassette Densuke” TC-2850SD,
a portable stereo recorder

RS-275U, the world’s first Compact
Cassette deck with a direct-drive motor

RS-1500U, a zero-loop,
open-reel tape recorder

4

5

6

7

8

9

Panasonic
Company
History Office
Panasonic
Company
History OfficeSony Archives

Sony Archives

Panasonic
MuseumSony Archives

The world’s first high-level cassette deck with a direct-drive capstan motor. Improved tape
In storage feed precision improved factors such as wow and flutter; this contributed to the improved
performance of later Compact Cassette machines.
A high-grade open-reel tape deck that achieved stabilised tape running performance withIn storage a zero-loop tape running system. Equipped with a DC direct-drive system on the capstan
developed for turntables.

machines an ultra-high quality of sound that would have been difficult to achieve with analogue
technology. Priced at ¥480,000.
A battery-operated, portable stereo tape recorder capable of recording in stereo. Used Dolby NR
other features to achieve a level of sound quality rivalling that of ordinary tape decks. A popular
On display andmodel with an inbuilt microphone amplifier, playing a major role in starting the “live recording boom”.
Priced at ¥52,800.

On display VTRs in the Betamax and U-matic formats. The harbinger of digital audio, giving consumer

An audio unit enabling PCM digital recording and playback at home in connection with home-use

on sale at a price of ¥10,000 at a time when popular-model, home-use machines werebeing sold for around ¥20,000. It became very popular and took a large share of the market.

On display No. 4 and a tape speed of 4.8cm/s. Its piano-key buttons made it very easy to use. It went

A small, battery-operated tape recorder for home use, with a dedicated reel called the

A small-scale tape recorder with an inbuilt microphone capable of being operated with
On display one hand. This model maximised the small size of the Compact Cassette and was usedby the crew aboard the Apollo 10 spaceship.

The world’s first record turntable system to have a DC direct-drive motor developed and
On display incorporated into it. It incorporated control technology for slow rotation speeds andbecame the basis for direct drives in other AV equipment.

1970

SP-10, the world’s first direct-drive turntable

3

Panasonic
MuseumJapan’s first domestically-produced open-reel tape recorder for home use. There wereSony Archives On display two types: the A type, with a limiter (limiting amplifier) and the B type, without a limiter.
The tape was developed at the same time and consisted of iron oxide on a paper base.

1950

G model open-reel tape recorder2

The world’s first “headphone stereo”. The combination of a dedicated playback taperecorder and lightweight headphones drastically changed the way in which people all
On display over the world listened to music; the good sound quality and the concept of listening tomusic anytime, anywhere was especially appealing to young people. The pet name“Walkman” was even accepted into the Oxford English Dictionary.

Resource
StatusSony Archives

Location

1979

Year
manufactured

TPS-L2, the first Walkman

Name

1

No.

List of Registered Devices

Tape Recorders

National Museum of Nature and Science
Systematic Examination of Technology Report, Volume 17
20 August 2012
■ Editor: 	National Museum of Nature and Science (Independent Administrative

Institution)
Center of the History of Japanese Industrial Technology(Under charge of: coordinating editor: Takayuki Nagata; editor: Toshihiko Okura)
English version: Osamu Kamei■ Publisher: 	National Museum of Nature and Science (Independent Administrative■ Printer:

274

Institution)
7-20 Ueno Park, Taito-ku, Tokyo 110-8718
Tel: 03-3822-0111(Japanese version) Shinkousoku Printing, Inc.
Translation and English version: WIP Japan Corp.

National Museum of Nature and Science
Survey Reports on the Systemization of Technologies; Vol. 17 August 2012

Historical Development of Magnetic Recording and Tape Recorder275