The Washington times. [volume] (Washington [D.C.]) 1902-1939, 1928-10-15

engineering progress.
There are many minor refine
nents intended to produce the maxi
mum efficiency, ruggedness, sim
plicity and reliability, due to the
research and engineering back of
the Freshman line.
In meeting the trend towards
greater volume, the Freshman engi-
neers decided to go directly to the
largest power tube available for
broadcast reception. namely the $50
type, with an undistorted output Of
we'll over watts at the working
voltage applied in this case, as
AGAINST q tenth that output for the
usual UX.171-A operating at a safe
voltage.
Super Power Amplifier
This. empower amplifier tube
b employed in the Freshman type
n receiver chassis, which comprises
six A-C tubes as follows: three
equaphaee stages of high gain radio
frequency application. detector,
= first audio stage, and the ESQ
power tube.
The components, including the
power supply unit. are contained in
4 neat metal cabinet with hand
some two-tone finish and bronze
tace plate framing the Illuminated
Belector dial and knob, and with
switch and volume control knobs
en either side, in the case of the
popular priced table model. Access
10 the tubes and internal details is
gained by removing the lid.
Connections are made by means
IF cord and attachment plug to the
nearest electric light socket or out
let, and to binding posts for antenna
ana ground, as well as to tip jacks
Tor the magnetic type 1oud-speaker,
N to q jack for the dynamic type
Dud-speaker, through inconspicuous
openings in the metal case.
The extreme selectivity and
sensitivity of this particular circuit
are obtained through the unique
Freshman Equaphase method of
stabilizing the radio-frequency
-ircuits.
Oscillation Eliminated
Instead OF neutralizing, grid
suppressor, or loser methods,
he equaphase arrangement elm
llates the cause of oscillation
trough an ingenious compensating
network of resistance, inductance,
and capacity developed by George
Eltz, vice president in charge OF
engineering of the Charles Freshman
Company. In fact, the equaphase
scheme Of sterilization, together
With the use Of properly engineered
.adio-freQuency transformers, pro-
sides a gain OF about per stage,
rs compared with 3 or less in the
usual popular-priced receivers.
The audio-frequency amplifier has
1kewise been the subject Of
original research and engineering.
Freshman engineers have studied
ne causes of distortion in the
usual atfdio transformer-coupled
implifier, and have traced them for
he most part to overloaded tubes
Ind saturated transformer cores.
Lne FORMER factor has been taken
are Of by using proper voltages
IN the tubes.
The latter factor has been
solved by the novel use of
thoroughly Tapped TRANSFORMER
amlnatfons, instead of the usuaI
suited laminations. In this manner
IL possible to prevent satGration
the transformer core, while
algh volume level is autonatica1l1.l
maintained. The thorough lappine
transformer Examinations. al.
:nougn involving ingeniuos produc-
ION methods, has proved far more
.IIsctlVe than the use of speciaI
ING costly nickel steels or bulky
Volume Regulated
IN addition TO eliminating core
iaturation. the Freshman engi.
ieers have worked out the most
teslrable chara cteristics in the sudio
IansIormers employed. Thus the
tmpllIlcatlon curve in the Freshman
Lualo amplifier starts off at so.
Win modest volume, rising tn good
'oiume at 40, and continuing it's
apId rise to a high level at 175
ycles, when the curve fIattens nut
.hd Is maintained to 10000 cycles.
- 'sn tnere is little music below
20 cycles, nothing is really sacri-
1ced IN this audio amplifier.
IN TACT. with a selected speaker
Iuch as the magnetic Or the dvna.
nle type built into the Freshman
loor model sets, there is a remark
tbie bass note response and nat
lral depth, without danger of over.
oading.
The power supply unit of the
dodel n receiver chassis utiIizes tho
lA-2Sl half-wave rectifier tube. sun.
nylng from as to $50 volts for The
hate Of the U&-250 tube, as well
Is the B and c requirements for
ne entire receiver. Filament and
ieater windings supply the raw A.C
CIV Toltages for the tubes. The
sUfrent drain on the rectifier is
rom 90 TO 20 milliamperes. so that
ne rectitler is running we'll within
Is rating. for maximum life The
lower transformer runs quite cool
ne litter condensers are of 1Oo0.
f.ot rating, so that a large factor
u safety is Incorporated in This
power unit for satisfactory and
ong service.
Mad in Various Types
Inc FRESHMAN Model y chassis iS
made up IN various models. ranging
rom the metal case table tvne
.hich sells for Sis, to the floor
abinet type with high-grade Peer.
PISS dynamic speaker, which sells
or s195. ''''''
Then there is the Freshman AIvs.
cry Set. which aroused so much
interest at the r. NJ. A. trade show
Chicago several months ago tho
ietails of which have been jealously
'uarded by the Freshman en-.
pneers until the present time. How
yer. with the introduction of this
81 to the radio trade, the details
re now available.
The Mystery Set is none other
han the Freshman Model O chassis
which is an sll-electric receiver
Utilizing the UX.222 shield.grid
ube, in combination with the usual
JX-226 and UY.227 A-C tubes. and
he UX-171-A power tube. The