Onkyo A 812EX (1987)
An integrated amplifier released in June 1987 with discrete output stages, dual-mono power supplies, and specialized circuitry for CD sources.
Overview
The Onkyo A-812EX is an integrated amplifier released in June 1987. It combines a preamplifier and power amplifier in a single chassis with a dual-mono construction, using separate power supplies for the left and right channels. Designed to handle both analog and digital sources with precision, it includes a dedicated CD direct switch and S.I.T. (signal in phase transformer) on the CD input to reduce digital noise. The amplifier supports both MM and MC phono cartridges and features Onkyo’s Twin Turbo Tone Control to enhance bass and treble response 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 uses a dual-mono construction with separate power supplies for each channel and a direct-coupled output stage powered by a high-current supply. It features discrete output transistors with a large power supply circuit and HighfT power transistors for low-impedance drive capability. A linear switching method reduces crossover distortion, while a delta turbo power supply filters AC line noise. The CD input includes a gold-plated terminal and S.I.T. (signal in phase transformer) to suppress high-frequency digital noise. The CD direct switch bypasses tone controls and input selectors for a cleaner signal path. The phono stage uses a discrete MM design with low-noise FET input and includes an MC/MM switch for compatibility with moving coil cartridges. Twin Turbo Tone Control allows independent adjustment of ultra-low frequencies (±15 dB at 50 Hz) and extended highs (±6 dB at 10 kHz).
Reception
The A-812EX is praised for its clean, detailed sound and solid build quality. It is considered a good value in the used market, though some users note it can sound slightly bright when paired with certain speakers.
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