Dynaco SCA-35 Stereo Control Amplifier
I got this picture from eBay auction Item #292794535.
The SCA-35 Stereo Control Amplifier is a complete stereo preamplifier and stereo power amplifier, combined on a single chassis with a single power supply. It uses premium grade components conservatively operated. The preamplifier printed circuit module amplifies the selected low level signal for each stereo channel through two stages (the two halves of a 12AX7 tube). Dual tone controls consist of passive networks, each encapsulated in a PEC. Each power amplifier, on a separate printed circuit module, uses a 7199 tube and two 6BQ5 output tubes, along with an optimized (Dynaco Z-565) transformer. A single cathode resistor is used for all four output tubes, which necessitates matching of the tubes.
The power supply uses a transformer and silicon diode full wave rectification, and provides individual hum adjustments for each channel on the back panel, along with two ac convenience outlets. The front panel is champagne gold, anodized aluminum, with die cast knobs, and includes switches for mono-stereo, loudness compensation, filter, and power.
Inputs: Low and high level magnetic phono, ceramic phono, NAB 7-1/2" tape
head, radio, tape, spare
Outputs: Tape, 8 and 16 ohm speakers, center channel loudspeaker, headphone provision.
Controls: Selector, Volume, Balance, Blend, Individual Treble and Bass for each channel, Tape Monitor, Loudness, Scratch Filter, Power.
35 watts continuous;
45 watts IHF music power (both channels).
Frequency Response: ±.5 dB 10 cps to 40 kc. Response not affected by position of volume control.
Power Response: 20 cps to 20 kc without exceeding 1 percent distortion within 1 dB of 17.5 watts, each channel)
Tone Control Range:
±12 dB at 15 kc;
±12 dB at 50 cps.
Sensitivity for rated output:
2.5 mV at tape head;
4 mV at low level magnetic phono;
1 volt at high level.
IM Distortion:less than 1 percent at 17.5 watts (each channel), less than 0.2 percent at average levels.
Hum and Noise:
70 dB below 10 millivolt input for rated output on low level inputs;
80 dB on high level.
Power consumption: 110 watts, 120 volts, 60 cycle AC (120/240 volt, 50/60 cycle operation available with optional PB-028 transformer).
Tube complement: 12AX7/ECC83 (2), 7199 (2), 6BQ5/EL-84/7189 (4)
Silicon diodes: 500 mA, 1000 PIV (2)
Essentially a re-packaging of the PAS and Stereo 35 units with redundant circuitry eliminated and the new front panel and knobs added. Introduced in 1963. Thanks to Ned Carlson from Triode Electronics for the scans of the classic reviews! Also thanks to Mark McNally for transcription of the specs and description reproduced here.
click here to see the 1964 review of the SCA-35 in Stereo Reviewmagazine.
click here to see the Stereo Review magazine lab test data.
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Copyright © 2000 Greg Dunn