Technics SU-A707
A late-1980s Technics integrated amplifier built on the company's Class AA topology. It is a parallel-amplifier design that separates voltage gain from current delivery, so it gets low-feedback linearity and high power output together.
Overview
The SU-A707 belongs to Technics' Class AA integrated amplifier lineup, along with the SU-A800 and SU-A900. Class AA is a Technics-specific topology. It is not Class A and it is not A/B. It uses two parallel amplifier stages. A "voltage amplifier" stage handles signal gain with low feedback and tight linearity. A "current amplifier" stage handles output current on its own. A special bridge circuit connects the two, so the voltage stage doesn't see the reflected complexity of the power-amp load.
The claim was that Class AA removed the trade-off between low-feedback linearity (good for sound quality) and high power output (which usually needs more feedback). In subjective listening tests, Technics Class AA amps from this era are generally regarded as cleaner and more transparent than typical Class A/B integrateds at the same price point.
Specifications
| Type | Class AA integrated amplifier |
| Power | ~70 W/ch RMS, 8Ω, both channels driven |
| THD at rated power | 0.005% |
| Frequency response | 5 Hz – 100 kHz (±1 dB) |
| S/N ratio | ~108 dB (Aux), ~80 dB (Phono MM) |
| Phono input | MM + MC |
| Inputs | Phono ×2, Tape ×2, CD, Aux, Tuner |
Applications and Legacy
These amps came out of late-1980s home stereo systems and Japanese-market enthusiast hi-fi. Working examples trade for $200-400. The Class AA circuit has aged well. None of the legendary failure modes of some 1980s designs apply here, and the unit responds well to standard service (electrolytic refresh, switch cleaning).
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