The Fisher
Master Audio Control, Model 50-C has been designed to specifications so far
beyond those of the ordinary unit of this type, that they will long serve as
the ultimate standard of comparsion. In flexibility, flawless performance,
beauty of appearance and workmanship, the 50-C is a masterpiece. In sctual use,
its performance will be limited on;y by the quality of the associated
equipment.
The Fisher
Model 50-C features high gain with extreme reserve output voltage.
Intermodulation distortion is so low as to be virtually unmeasurable. The
self-contained power supply, completely shielded with DC for all filaments,
results in a hum level that is inaudible even under extreme operating
conditions. The circuit is all-triode, with fully shock-mounted tubes.
Cathode-follower input and two cathode-follower output stages assure isolation
of all control circuits, plus independence from load conditions, lead lengths,
etc. The Model 50-C can be used with any amplifier.
Specifications:
Phonograph
Preamplifier: Has two cascaded triode
stages.
Inputs
(Total of five):
3 x
high-level inputs (0,5 megohm)
1 x
low-level magnetic phono input to match all makes of cartridges.
1 x
microphone input (2,2 megohms)
Output
Impedances (Both recorder and main audio outputs are from cathode followers,
permiting lead lengths up to 200 feet. Recommended load impedance):
100,000 ohms or greater, 7500 mmf or less.
Maximum
Gain:
From high
level input: 22,5 dB
From low
level input: 50 dB
Harmonic
Distortion:
0,02% at 1
volt,
0,05% at 5 volts
0,15% at 10
volts
0,4% at 15
volts
Intermodulation
Distortion:
0,08% at 1
volt
0,2% at 5
volts
0,5% at 10
volts
1,6% at 15
volts
Frequency
Response: 20 Hz - 20,000 Hz ±1 dB, (with controls in uniform response
position)
Hum and
Noise level:
On radio
input - better than 100 dB below normal signal (2 volts output) with volume
control at zero.
Better tnan
90 dB below normal signal with volume control at maximum.
On phono
input -66 dB below output with a 10 mV input signal.
Controls
(Total of eight):
Volume
Control; operates either conventionally or as a Loudnes Control accurately
calibrated to the reciprocal of the Fletcher-Munsen curves
Loudness
Control Switch; eliminates loudness compensation when desired
Selctor
Switch; has five position (see Inputs above)
Low and High
Frequency Equalization Switches; provide independent adjustment of low
frequency turnover and high frequency roll-off (16 combinations)
Bass and
Treble Tone Controls; produce up to 16 dB of boost or attenuation at 50 and
10,000 cycles respectively. Can be set for uniform response
Power
Switch; operates self-contained power supply and three spare AC receptacles.
Five
Independent Level Controls; equlize various input signal levels and permit
optimum loudness control setting.
Power
Supply: Self-contained and completely
shielded, including a full-wave selenium rectifier for B-plus and bridge-type
selenium for Dc filaments
Power
Source: 105 -125 Volts, 50 - 60 cycles
Tube
Complement: 2 x 12 AX7; 1 x 12 AU7
Chassis: is of etched aluminum
Dimensions (W x H x D): 14¾ x 3½ x 6⅛ inches