Onkyo A 812EX (1987)
An integrated amplifier released in June 1987 with discrete output stages, dual-mono power supplies, and special circuitry for CD sources.
Overview
The Onkyo A-812EX is an integrated amplifier released in June 1987. Preamp and power amp share one chassis. The construction is dual-mono, with separate power supplies for the left and right channels. It handles analog and digital sources, and it has a dedicated CD direct switch. The CD input also has an S.I.T. (signal in phase transformer) to reduce digital noise. It takes both MM and MC phono cartridges. Onkyo's Twin Turbo Tone Control adjusts bass and treble independently.
Specifications
| Maximum practical power | 105W + 105W (6 ohm, EIAJ) |
| Rated Output (CD → SP Out, both channels driven) | 72W + 72W (6 Ω) |
| Rated Output (CD → SP Out, both channels driven) | 60W + 60W (8 Ω) |
| Dynamic Power | 135W + 135W (2 Ω) |
| Dynamic Power | 78W + 78W (8 Ω) |
| Total harmonic distortion | 0.08% or Less (at 1 kHz, Rated Output -3dB) |
| S/N ratio (IHF-A, short) | Phono MM:83dB |
| S/N ratio (IHF-A, short) | Phono MC:65dB |
| S/N ratio (IHF-A, short) | CD, Tuner, AUX/Video, Tape, DAT : 90 dB |
| Phono maximum allowable input MM | 150 mV (1 kHz, 0.5%) |
| Tone control Bass | ± 10 dB (100 Hz) |
| Tone control Treble | ± 10 dB (10 kHz) |
| Tone control Twin Turbo | ± 15 dB (50 Hz), ± 6 dB (10 kHz) |
| Muting | -20dB |
| Speaker switching | A, B, A + B |
| Input Sensitivity / Impedance Phono MM | 2.5mV/50k Ω |
| Input Sensitivity / Impedance Phono MC | 0.35mV/330 Ω |
| Input Sensitivity / Impedance CD, Tuner, AUX, Tape, DAT | 150mV/50k Ω |
| Inputs | 4 line inputs, 1 phono input |
| Outputs | 1 tape output, 1 pre-out, 1 headphone output |
| Power supply voltage | 100 VAC, 50Hz/60Hz |
| Power consumption | 115W |
| External dimensions | Width 435 x Height 120 x Depth 272 mm |
| Weight | 6.7kg |
| Frequency response | 20Hz-20kHz (±0.5dB) |
Design
The A-812EX is dual-mono, with a separate power supply for each channel and a direct-coupled output stage run from a high-current supply. The output transistors are discrete, backed by a large power supply circuit and HighfT power transistors for low-impedance drive. A linear switching method reduces crossover distortion. A delta turbo power supply filters AC line noise. The CD input has a gold-plated terminal and the S.I.T. (signal in phase transformer), which suppresses high-frequency digital noise. The CD direct switch bypasses the tone controls and input selectors, so the signal path is shorter. The phono stage is a discrete MM design with a low-noise FET input, plus an MC/MM switch for moving coil cartridges. Twin Turbo Tone Control adjusts ultra-low frequencies (±15 dB at 50 Hz) and extended highs (±6 dB at 10 kHz) independently.
Reception
The A-812EX is praised for a clean, detailed sound and solid build quality. It is considered a good value on the used market. Some users say it can sound slightly bright with certain speakers.
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