Onkyo Integra A-810 (1979)
At 20.3 kilograms, it is a dense, heavy amplifier, built to keep distortion down.
Overview
The Onkyo Integra A-810 is an integrated amplifier released in 1979 as part of Onkyo's premium Integra line. It was built to deliver power and keep distortion low. Rated output is 110 watts per channel into 8 ohms, 20 Hz to 20 kHz, both channels driven. The damping factor is 100 at 1 kHz into 8 ohms, which gives tight control over demanding speakers. Power bandwidth runs from 5 Hz to 100 kHz (IHF-3dB, THD 0.2%), well beyond what most amplifiers were expected to do, and it suggests a design tuned for transient accuracy and high-frequency ease.
Distortion is where the A-810 stands out. Total harmonic distortion is rated at just 0.008% across 20 Hz to 20 kHz at full rated output, dropping to 0.006% at half power. Those figures rival far more expensive competition. The phono stage numbers are better still: 0.003% THD for MM and 0.01% for MC inputs at 3 volts. The A-810 takes both MM and MC cartridges directly. Input sensitivities are 2.5 mV/47k-100k Ω for MM, 2.5 mV/100 Ω for High MC, and a very low 130 μV/100-330 Ω for standard MC, so a wide range of moving coil cartridges works without external step-up transformers. Signal-to-noise ratio is 86 dB (IHF-A, input short) for MM and 100 dB for line-level inputs. The MC stage manages 69 dB, which is the usual noise price of low-output cartridges.
The A-810 uses Onkyo's W / Super Servo system in both the power amplifier and the MC-compatible equalizer stages. It is meant to eliminate DC leakage and power supply impedance effects that degrade sound quality. A direct tone circuit bypasses the tone amplifier entirely, so the signal avoids the degradation tone controls usually introduce. Instead of an extra gain stage, there is a "softness circuit" with three selectable tonal characters. The tone controls give ±8 dB at 70 Hz and 20 kHz, loudness compensation is +6 dB at 100 Hz, and a subsonic filter switches between 15 Hz and 20 Hz (6 dB/octave) to block turntable rumble.
The power supply is a big one. A large twin-wound transformer feeds a low-impedance rectifier system using multi-tab Chemi-Con capacitors, mounted directly to the PCB to minimize inductance. Heavy copper bus bars distribute power and ground across sections, reducing impedance and improving stability. The power amplifier is a 3-stage Darlington configuration in a double push-pull layout, which Onkyo claims pushes crossover distortion out of the audible band. A linear switching method keeps the circuit linear without altering bias. An auto-tracking bias system monitors temperature differentials across components to hold distortion low during operation. Non-magnetic materials are used throughout to prevent harmonic coloration.
Inputs are phono (MM/MC), tuner, AUX, and two tape loops, each with standard 150 mV/47 kΩ sensitivity. Tape outputs deliver 150 mV/2.2 kΩ, and a preamp output provides 1.5 V/600 Ω for driving external power amplifiers. The unit consumes 200 watts under load and runs on 100 V AC (50/60 Hz). It has one unswitched AC outlet (200 W) and two switched outlets (total 200 W) for source components. The chassis measures 435 × 170 × 424 mm, and the A-810 weighs 20.3 kg. It originally retailed for ¥145,000 around 1980, which put it at the high end of the Japanese market.
Historical Context
The Onkyo Integra A-810 arrived in 1979 as a new addition to the Onkyo Integra series of integrated amplifiers.
Japanese manufacturers were pushing solid-state amplifier technology hard in this period. Onkyo stood out with the W / Super Servo system and close attention to power supply design. The A-810 combined high power output with very low distortion and a flexible, high-gain phono stage that handled both MM and MC cartridges, which was rare in integrated amplifiers at the time.
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