Integrated amplifier SPEC RSA-M99
Author: Amré Ibrahim Photography: Rolf WinterSPEC-tacular
No amplifier range has received
quite as much prejudice in recent
years as Class-D concepts. Regardless, its advantages have become
increasingly hard to ignore, so convincing in fact, that many audiophiles predict the end of the tube amplifier era. Such prophecies are due
to equipment like this.

Many audiophiles still turn their nose up at any mention of ClassD. Let’s not forget though, that most won’t have invested any realtime in understanding the mechanics of switching amplifiers. To
be honest, I wasn’t exactly missing a Class-D amp amongst my own
rack, but there is no denying their rapid development. Savvy ‘digitals’ are producing impressive results – compact design, minimalenergy consumption, high user flexibility and best of all, notabletonal advancements. In the past, descriptions of the Class-D soundquality were often associated with unfavorable terms like ‘sterile’
and/or ‘artificial’. Recent reviews however, seemed to have switched
tone, now using attributes such as ‘emotional’, even ‘musical’.
Whilst this may seem like the result of clever marketing strategies,
some of the latest tech fair demonstrations have proven otherwise.
At the High End 2018 show in Munich, for example I was particularly impressed by the performance of Dynaudio speakers pairedwith NAD amps. Similarly so, the Neo speaker from Genuine Audio – based on active Class-D technology – left me dazzled with
raw dynamism and subtlety alike at this year's show. In terms of theHigh End show 2019, I count the showrooms of Audio Note Kon-do with Living Voice and Boenicke Audio amongst
my personal favorites. Both brands offered a playback
experience that felt holistic and complete despite thesuboptimal room conditions. Whilst this holistic sensibility was based on completely different sound philosophies in both cases – the Kondo/Living Voice presentation focused on phono, tube amplifiers and highefficiency speakers while Boenicke Audio presented a
CD drive, a DAC, switching amplifiers and speakers
with ‘average’ efficiency – their tonal plasticity, fluidity and especially their emotional reach were also notably similar.
On the ground floor, situated in one of the smaller
rooms of the fair, I was excited to discover the exciting performance of the gear presented by AudioTweaks. Based in Sellingen in The Netherlands, AudioTweaks is the distributor for the Japanese audio
manufacturer SPEC Corporation in Germany. I firstencountered SPEC and AudioTweaks’ CEO Piet deVries three years ago. I had been curious about theSPEC RPA-W7EX model and how it would performwith the Boenicke W8 SE+. De Vries kindly let me
test two of his power amplifiers, which by the way also work as monoblocks. I still remember finding it
extremely hard to return those amps amplifiers. The
RPA-W7EX was my first experience of Class-D components worthy of comparison with the tonal flair ofa good push-pull tube amplifier. I hindsight thiswasn’t exactly surprising, considering what else wason display at the aforementioned AudioTweaks
room in 2019. SPEC devices sat alongside renowned
by Leben Hi-Fi tube amplifiers – both manufacturers represented by the same Japanese export company which is Muson Project.
SPEC is a relatively young audio manufacturer founded by Syuzou Ishimi in 2010 in Tokyo. Ishimi’s
company now has 15 employees and is based largelyon the sound philosophy of Shirokazu Yazaki, who
has since retired. Yazaki was already leaving a markon the high-end market before the birth of SPEC.
His inventions include the famous A-7300 tape machine by TEAC, the DV-AX10 DVD/SACD player
which received numerous awards as well as the CT95 tape deck by Pioneer – preferred by many tapebuffs over the mighty Nakamichi Dragon. The legend goes that Yazaki spent many years developing
and optimizing his own music system that was basedon single-ended tube amplifiers and Onken hornspeakers. Now when such creative spirits take it uponthemselves to develop a Class-D amplifier, we can’t
but expect outstanding sound results. No wonderthat one of the first SPEC switching amplifiers thatcame on the market, the RSA-M3EX model, caused
instant ripples amongst specialist media – praisedfor its enormous ’musicality’ and compared to thesound of the Kondo Overture. More on that later.

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Integrated amplifier SPEC RSA-M99

The iron case is manufactured by an experienced specialistof the Yamagata prefecture according to exact SPEC specifications. The Japanese manufacturer emphasises how
their amplifiers are to be considered musical instruments.
By that logic, the solid spruce base chassis provides theamplifier with an additional, instrument-like resonant surface. The three-point footing system comes with cone-shaped, rounded feet made of maple with hickory core, to counteract unwanted vibrations. The centre foot is also earthed

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The integrated amplifier RSA-M99 succeeds the
RSA-M3EX, the switching technology of which was
optimized over a six months period. According tochief engineer Tsutomu Banno this new model exceeds the RSA-M3EX in both tonal range and accuracy. In response to all of my questions regarding circuit or components, Banno referred to the company
design principle, the so-called ‘Pure Direct System’,meaning that every detail no matter how small wasalways aimed at making the amplifier sound as ‘natural and musical’ as possible – short signal paths andstraightforward circuit design being key. Whilst SPECis transparent about the term ‘Class-D’, Banno insistson the RSA-M99 being in fact an analogue amplifier.
Beginning with the source signal, which he explains,unlike most amplifiers doesn’t pass through therheostat of a mechanical potentiometer. The Japanese manufacturer chooses not to use such volume regulators nor remote controls, which typically imply adecrease in sound quality. However, SPEC does offer
the cabled RSR-1, a remote control option with infrared receptor that comes at an additional price of 700
Euros. At the preamp stage the RSA-M99 uses an electronic resistor network made up of 256 layers to generate an analogue control signal. Initially, this runs
through an analogue pulse width modulation at thepower amp stage before reaching the Class-D driverstage and finally arriving at high-speed switching power MOSFETs. With an output of 2 x 120 watt into 4ohm, 90 watt into 6 ohm and 60 watt into 2 ohm respectively, this amp generates enough power and stability to control demanding speaker designs. Tsutomu Banno is convinced that from the perspective of‘dynamics’, speaker diaphragms ‘follow’ sound signals
from well-conceived switching amplifiers more easily than signals from tube or transistor-based amps.
Speaker diaphragms are triggered extremely precise
and fast due to the very low output impedance ofClass-D designs as well as its ability to absorb thecontrasting electromotive forces of the speakers.
I find it touching how passionate the chief SPEC engineer is about the RSA-M99 and how much care anddedication the entire company deploys in their pur-xxx
suit of ‘true sound’. I have been aware of the impeccable finishes typical of this manufacturer since encountering the RSA-M3EX power amplifier and found the same level of quality with the RSA-M99
model. Featuring an iron case exterior with aluminium front panel and dials, only one word describes
what we’re dealing with here: perfection! Fitted with amechanism derived from aircraft manufacturing thatprevents accidental start-ups, the on/off toggle switch
alone deserves an award for haptics. The metal casing,meanwhile is supported by a solid spruce chassis withthree cone-shaped maple feet. I am told that the inspiration for using the two types of wood came fromviolin making. Width and consistency of the wood arealso not accidental: the added base plate functions as
an analogue, instrument-like sounding board that together with the three-point connection to the rackand hickory core of the maple footing, counteracts
unwanted vibrational effects. ‘Banno-san’ as the chiefengineer is also lovingly referred to by non-Japaneseclients, offers an almost romantic explanation: SPEC,he suggests, is as much an instrument maker as a manufacturer of amplifiers. It comes as no surprise that
Mr. Banno is also a passionate cellist.
As to be expected, craftsmanship is as stellar on theinside as it is outside. Meticulously crafted, the circuit board based structure deserves the highest ofComponents:
Turntables: TechnicsSL-1210M5G, TW AcusticRavenGT2 Tonearm: Robert Fuchs 12” Cartridges: Grado Statement Statement
2, Lyra Kleos, SteinMusic Aventurin 6, AEC London C-91E
Headshells: Acustical Systems Arché 5D, SteinMusic Ametrin
1, OyaideHS-TF Carbon Phono Preamplifier: Rike Audio Natalija Pre 2 MC Step-up: Phasemation T-300 Audio CD Player:
Lector CDP-707 with PSU-7T, OppoBDP-103 Integrated Amplifier: Kondo Overture PM-2i Speakers: Boenicke Audio W11 SE+
Cables: Kondo Vc-II, Kondo Operia SPc-2.5, Kondo ACc Persimmon, Boenicke Audio S3, Boenicke Audio IC3, cinch cable andLS8 speaker cable by Biophotone, Acoustic System Liveline cinch
cable, fastaudio Black Science cinch cable, Bastanis Meta & Epilog cinch cables Tuning Accessories: Pi Perfect Interface turntable mat by Steinmusic, Audiophil-Schumann generator, TAOC
racks, SteinMusic harmonizer and Blue Suns, Acoustic Revive RL30 Vinyl record demagnetizer, Audiodesksysteme Gläss Vinyl Cleaner PRO and Sound Improver, Audio Exklusiv d.C.d. base and Silentplugs, FPH-Akustik vibration absorbers, Herbie’s Audio Lab
Tenderfoot, Audio Laboratory LittleFoot’s/BigFoot’s, Duende-Criatura damping rings, fastaudio absorber, Acoustic System resonators, MFE power socket, AMR-, Furutech- and AHP micro fuses,
Biophotone Magic Akasha Quantum Power Plugs, Acoustical
Systems SMARTractor and HELOX record clamp, complete tube
supply by BTB Elektronik
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Left: Prevents electromagnetic interference:transformer section, circuit board with lowpass filter and choke circuit as well as theprinted circuit boards featuring the pre andpower amplifier sections are all shielded individually

Above right: Red Cactus oil paper capacitors
were especially developed by SPEC in collaboration with US manufacturer Arizona Capacitors. These are designed to meet the special requirements of SPEC's Class-D design. In
addition, the Japanese manufacturer uses
top quality ruby mica capacitors, renowned
for providing an extraordinary stable soundas well as Hibiki Ichi electrolytic capacitors
by Nichicon for their ‘fast’ and ‘natural sounding’ performance

Centre right: The low-pass filter coils were
custom developed in house and contain acore of carbonyl iron powder. Since Class-D
develops practically no heat, no heat sinks
are required, which results in less intensive
circuit complexity and shorter signal paths.
For this reason, the printed amplifier board
which includes power MOSFETs by Infineon
Technologies was mounted 'board to board"

Below right: No halfway measures: SPEC custom produces toroidal transformers in-house. The Japanese manufacturer promises
superior ‘musicality’ and dynamics that exceeds other available transformer concepts

No sound degradation caused by mechanical potentiometers: the resistor network is fitted with 256 layers and generates an analogue control signal. Four circuit boards holdthe LEDs for the circular lighting of the volume control andsource selector

SPEC refrains from using relay-based source selectors: forreasons of improved sound quality, the Japanese manufacturer prefers to use good old mechanical contact. Moreover,the selector switch is said to be meeting ‘high industry standards’ that are totally reliablepraise. All sections sensitive to electromagnetic interference are shielded by solid stainless steel casing.
Regarding components, SPEC doesn’t shy away fromhigh-end or custom-made additions either. Underneath the shielding I found custom low-pass filter
coils with carbonyl iron powder core developed inhouse, MOSFET power transistors by Infineon Technologies as well as Red Cactus oiled paper capacitors
manufactured by Arizona Capacitors according toSPEC specifications as well as ruby capacitors withhighest quality mica, exclusively sourced from thefoothills of the Himalayas. In addition, Special Hibiki Ichi electrolytic capacitors by Nichicon guarantee
the high standard of the SPEC circuit design. This
manufacturer definitely doesn’t want anything to dowith 1-bit digital modulation à la Delta Sigma: Aspreviously mentioned SPEC are committed to using
pulse width modulation (PWM), which instead of
digitizing the audio signal, analogue processes thesignal amplitude after passing the low-pass filter. According to Tsutomu Banno this method producesnoticeably better sound results than digital transmis-

sion particularly when more complex timbre structures are atplay. Equally important to him is the way power is supplied: “Agood PSU is important for all amps, but particularly crucial forClass-D designs, because their switching power supplies are directly connected to the speakers! Sound quality immediately relates
to the quality of the power supply in this case. This is why we only use custom-made, extra large toroidal core transformers thatare produced in-house.”
Regarding connectivity, the RSA-M99 integrated amp which canalso run as a power amplifier doesn’t leave much to be desired. Fitted with three cinch and two XLR inputs, it allows for a total of five source devices. Considering the list price of 10500 Euro, somemight rightly miss an integrated phono stage for MM cartridges.
Anybody looking for fully balanced signal passing won’t be getting
it from the RSA-M99 either. The XLR signal routing of this amp isjust not designed to run fully balanced. But that’s just about the
only conceptual flaws I could find, while intense listening sessions
didn’t reveal any sound-related weaknesses at all with this Japanese jewel! As a result of its high damping factor and less surprising
fact to those familiar with Class-D designs was the unyielding control with which the RSA-M99 was able to power my Boenicke W11
SE+. What seems amazing however, is the perfect timing. In my
experience some Class-D concepts are weak in this area, often displaying instantly audible distortions from any imprecisions thattake place at the nanosecond level of high frequency technology.
This timing teams up with what has to be called a SPEC-tacular
holographic representation, which definitely meets that of my
Kondo Overture PM-2i at eye level: the scale and presence of thesound is phenomenal!
For example, Bread’s ‘Baby I’m-A Want You’ (Mobile Fidelity Sound Lab/Elektra/Sieveking Sound, UDSACD 2205, USA 2019, Hybrid-SACD) album from 1971 stands out for its clear spatial structuring. The RSA-M99 allows the sound to disconnect from the
speakers and create a vast, far-reaching soundscape that remains
transparent to its edges, enabling the free unfolding of both voices

Even if an integrated phono amp would have been desirable: featuring fiveline inputs, two of which are XLR (unfortunately not balanced), the RSA-M99
which can also run as a power amp offers enough connection flexibility. A
remote control, which due to improved sound quality uses an infrared receiver cable, can be purchased separately

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Integrated amplifier SPEC RSA-M99

and instruments. I’m sure it’s no coincidence that thismakes me think of the famous cigarette ads of the 80s– cowboys on horseback, a whiff of freedom (or something like that). What makes the transparency of
the SPEC device so enjoyable though, is the refrainfrom detached-seeming ‘astral ethereal’ sound qualities. Instead, the sound is grounded and has a bodily
presence. Tsutomu Banno certainly wasn’t exaggerating when describing the efforts that had been madeto make wood sound like wood, metal like metal andfur like fur. To return to ‘Baby I’m-A Want you’, thetimbre produced by the SPEC Amp is the best representation of the Class-D category that I have had in
my rack. The drums sound real, the steel strings sound real, the stringed instruments sound real… andDavid Gates’ voice is as soft as intended, even if the
RSA-M99 is by no means a softie. If needs must, thisJapanese power house knows how to go for it. When
playing the electro house classic Cross (Ed Banger Records/Because Music, BEC5772110, Europa, 2007, 2LP) of the French duo Justice, it really flexes its muscles. The massive sound architecture of ‘Genesis/Let
There Be Light’ is transported to the speaker diaphragms with impressive stoicism and energy. Anycompression effects at high volumes? None! The RSAM99 just doesn’t seem to buckle – strong in the truest
sense of the word. I have a small tip though, if you areinterested in the RSA-M99 be careful about choosing
the right cables. I don’t really understand why, but it
seems to me that some Class-D amps are extremely
sensitive when it comes to wiring. For example, my
Acoustic System Liveline cables seem to thin out thesound a bit, which creates a lack of depth mostly in thebass range. In contrast, I’ve had a great experience
with the copper versions of the current Kondo generation, which includes the NF cinch cable Vc-II, theOperia SPc-2.5 speaker cable and the ACc Persimmon
power cable, which by the way, gave the SPEC an extra
dynamic boost. Whilst this cable trio ensures a balanced broadband performance, it also seemed to support the very ‘musicality’ of the amp so praised by
SPEC and Piet de Vries.
In addition to everything I have mentioned, theSPEC also demonstrates a wonderfully natural capa-

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city for dissolution and finely tuned ‘sense’ for dynamic distinction that is extraordinary. This becomesapparent when listening to Henryk Góreckis Sinphony N.3 op.36 as performed by Portishead singer
Beth Gibbons as solo soprano and the Polish National Radio Symphony Orchestra under Krzysztof
Penderecki (Domino/GoodToGo, WIGLP395X, UK
2019, LP). As a conceptual piece with the designation of ‘Lento’ and ‘Lento e Largo’, such display of sensitivity and capacity for ‘inner flow’ is obviously whatmakes the recording unfold in the lamenting, emotional force that it does, just as intended by Krzysztof
Penderecki.
The SPEC RSA-M99 is one of the best ‘tubeless tube amplifiers’ I know. It is also a perfect example of
how profound technical knowhow, dedicated passion for the product and an unfailing love of music has
driven the advancements in Class-D to where it
stands today.

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Integrated amp SPEC RSA-M99
Functioning Principle: Switching amplifier Inputs: 3 x Line(cinch), 2 x Line (XLR) Power Voltage: 2 x 120 W (4 ohm), 2 x 90
W (6 ohm), 2 x 60 W (2 ohm) Frequency Response: 10 Hz – 30
kHz Harmonic Distortion: 0,02 % (@ 1 kHz) Input Sensitivity:
300 mV Power Consumption: 215 W max. Special Features:
Red Cactus oiled paper filled capacitors by Arizona Capacitors (custom-made for SPEC), top quality ruby mic capacitors, Hibiki-Ichi
electrolytic capacitors by Nichicon, SPEC silicon carbide rectifier,SPEC low-pass filter coils with carbonyl iron powder core, Belden8470 copper wire for secondary power supply and loudspeaker terminals, Belden-1503A copper wire for audio signal, volume control that can be switched, volume and selector control withswitchable illumination, able to run as power amp, optional remote control RSR-1 with corded infrared receptor (700 Euro) Options:Silver only Measurements (W/H/D): 44/12,5/41,4 cm Weight:
16 kg Guarantee: 2 years Price: 10500 EuroContact: AudioTweaks, Piet de Vries, Wessingtange 9, 9551 XW
Sellingen, The Netherlands, Phone +31 650503610, audiotweaks.nl
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