Dynaco SCA-80 Stereo Control Amplifier
schematic pt. 1,
schematic pt. 2,
for the SCA-80. You may want to right-click (Mac users click/hold) to save these, as they will slow your browser down significantly.
The Dynaco SCA-80Q is an all silicon solid state stereo control amplifier of exceptionally high quality. It functions as the control center for all mono or stereo signal sources, such as a record player, radio tuner, tape recorder, television sound, etc., and provides output connections from two 40 watt power amplifiers for either two or four loudspeakers, as well as a front panel jack for stereo headphones. Thoughtful planning has provided exceptional flexibility with remarkable ease of operation.
The SCA-80Q incorporates special circuitry which enables Dynaquad™ 4-dimensional playback for increased realism from a four speaker system without any additional electronics. Alternatively it may be used as a conventional two channel stereo amplifier with provision for optional connection of a second pair of speakers in a remote location.
The SCA-80Q has been designed to be used under normal conditions without special safety precautions, just as if it were a high grade tube amplifier. There are no circuit breakers, speaker fuses, or other resettable devices to impede the use of the SCA-80Q under any reasonable conditions of use or abuse. This is achieved by using novel circuits (on which patents are pending) which automatically and instantly protect the amplifier.
The components in the SCA-80Q are of the highest quality to protect against failure, both now and for many years in the future. The transistors have been selected for minimum noise and distortion in sustained use. All parts are used conservatively with close tolerances to assure proper operation, and all four etched circuit modules in the kit have been pretested under actual use conditions to ensure that every unit, after assembly, will meet the specifications normally associated with laboratory prototypes.
The specifications of the SCA-80Q speak for themselves. The distortion at low levels is comparable to that of the finest tube designs, while the high power distortion remains inaudible. Specifications do not reveal all the facets of sound quality, however. In use with varying program material, the SCA-80Q justifies its design efforts to have qualities of ease and naturalness always sought and rarely achieved in solid state designs. There is no extra brightness or stridency which is unfortunately sometimes attributed to high fidelity sound, but rather there is an impression of limitless range and effortless handling of the highest power peaks.
Rated Power Output: 30 watts continuous average power per channel into 8 ohms, 20-20,000 Hz at less than 0.5% total harmonic distortion. Distortion decreases at lower power levels.
Power at Clipping, Single Channel, 1000 Hz, less than 1% distortion: 50 watts @ 8 ohms, 36 watts @ 4 ohms, 26 watts @ 16 ohms.
Intermodulation Distortion: Less than 0.5% at any power level up to 40 watts rms per channel into 8 ohms with any combination of test frequencies. Distortion reduces at lower power levels.
Half-Power Bandwidth: 20 watts per channel at less than 0.5% total harmonic distortion from 8 Hz to 50 KHz into 8 ohms.
Phono: ± 1 dB of RIAA curve @ 1 watt into 8 ohms.
High level: ±0.5 dB, 15 Hz to 50 KHz @ 1 watt into 8 ohms.
Hum and Noise:
Phono: More than 60 dB below 40 watts output.
High level: More than 80 dB below 40 watts output.
Input Sensitivity: 100,000 ohm load; 1.3 volts for 40 watts into 8 ohms.
Magnetic Phono: 47,000 ohms.
High Level: 100,000 ohm.
Tape Output:From Phono inputs, 10,000 ohms minimum load.Headphone Output: 8 ohms or greater.
From High Level inputs, same as source.
Phono Input Overload: 80 mV @ 1000 Hz.
± 12 dB @ 50 Hz;
± 12 dB @ 10 KHz.
Separation: 65 dB by IHF standards.
Semiconductor Complement: 20 transistors; 10 diodes.
Size: 13-1/2" wide by 12" deep by 4-1/4" high.
Shipping Weight: 18 lbs.
Maximum Power Consumption: 35 watts quiescent; 250 watts maximum; 50/60 Hz, 100, 120, 220, or 240 VAC.
Essentially a re-packaging of the PAT-4 and Stereo 80 units with redundant circuitry eliminated and a speaker switch added. A later upgrade, the SCA-80Q, incorporated the Hafler QD-1 synthesized ambience circuitry and relabeled output terminals for the rear speakers. It says "4-Dimensional Amplifier" on the front panel.
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Copyright © 2000 Greg Dunn