Sansui AU-D7
Eighty watts, a damping factor of 200, and a phono stage that pulls 250 microvolts off a moving coil - the AU-D7 is the integrated amplifier Sansui built when it stopped guessing and started measuring.
Overview
The AU-D7 is a stereo integrated amplifier from Sansui Electric Co., Ltd. It is documented in the company's own service manual alongside its smaller sibling, the AU-D5. Both were built around the same chassis and circuit boards. The manual lists shared part numbers for the F-3222 protector board, the F-3223 power fuse board, and the F-3233 control board, with separate stock numbers distinguishing the two models. The AU-D7 is the larger of the pair: 80 watts per channel into 8 ohms, both channels driven, from 20 to 20,000 Hz, with total harmonic distortion held to no more than 0.02 percent at or below rated output. That's a conservative rating for its era. The damping factor of 200 into 8 ohms, measured at 1 kHz with both channels running, says Sansui cared more about loudspeaker control than bench-racing numbers.
The power supply is where the AU-D7 separates itself from the AU-D5. The two models share a transformer footprint but not a transformer. The manual lists separate part numbers, and the filter capacitors differ as well - 15,000 microfarads at 63 volts for the AU-D7 against 9,000 microfarads for the AU-D5. Rated consumption is 270 watts, 340 VA, with a maximum draw of 380 watts. The mains fuse is a 6-amp part on 100-120 volt units and a 3-amp part on 220-240 volt versions. Anyone buying a gray-market example needs to confirm which voltage it was built for before plugging it in.
The frequency response is wide - DC to 300,000 Hz, +0/-3 dB at one watt from the AUX input. Most owners will never use that, but it points to a direct-coupled signal path with no output coupling capacitor in the way. The RIAA curve deviates less than the manual's stated tolerance across 20 Hz to 20 kHz. The phono stage covers both moving magnet and moving coil: 2.5 millivolts into 47 kilohms for MM, 250 microvolts into 100 ohms for MC. The MC input will take a maximum of 15 millivolts at 1 kHz before distortion crosses 0.1 percent, and the MM input tops out at 200 millivolts on the same basis. Signal-to-noise is quoted at 67 dB for the MC stage, 86 dB for MM, and 110 dB for the line inputs, all short-circuit, A-weighted. Channel separation runs 55 dB on phono and 90 dB on line inputs at rated power.
Line-level inputs are AUX, TUNER, and two tape play loops, all 200 millivolts into 47 kilohms. The tape record outputs deliver 200 millivolts into 47 kilohms or 600 ohms. Two tape loops means dubbing without repatching. The 4-pin input terminals for tape and the 6-pin terminal for phono, tuner, and aux date this amplifier firmly to its production era. The control set includes SUPER BASS, BASS, PRESENCE, and TREBLE, with the treble specified at ±6 dB at 15 kHz and the loudness compensation adding +6 dB at 50 Hz and +6 dB at 10 kHz when engaged. A power display on the front panel is adjustable via trimmer resistors on the power supply board. The service procedure calls for a 1 kHz sine wave and a specific voltage at the 8-ohm load: 25.3 volts for the AU-D7 against 22.8 volts for the AU-D5, which fits the two models' differing output levels.
The AU-D7 measures 148 mm high and 328 mm deep as a standalone unit, or 339 mm deep with rack mounting adaptors fitted. The adaptors stretch the width to 480 mm. Per the accessory list, the rack adaptors were supplied with black-panel models only, and the packing list confirms separate carton part numbers for silver and black versions. Packed weight is 12.6 kg for silver and 12.8 kg for black. The faceplate color is the only meaningful external difference between the two variants.
Protection circuitry centers on the F-3222 board, built around an HA12002 integrated circuit with a pair of relays and a peaking coil, plus a bank of diodes and transistors handling the sensing logic. The power amp board is the F-3221, the control board the F-3233 with a pair of 50-kilohm variable resistors handling presence and subsonic bass. The power supply board, F-3227, carries the 2SD358 and 2SC1845 transistors and a pair of 220-ohm, 2-watt non-inductive resistors.
Period advertising for the wider Sansui line leaned hard on the noise-and-distortion angle. A High Fidelity (November 1983, p.63) advertisement for the AU-D77X promised pure, true sound for listeners bothered by noise, hum, and distortion. It positioned that model beneath Sansui's 130-watt top-of-the-line AU-D11 II integrated amplifier, which gives some idea where a model like the AU-D7 sat in the hierarchy. The same campaign language ran in HiFi-Stereo (May 1984, p.35) and again in High Fidelity (July 1981, p.67). It is marketing copy, not independent verdicts.
The surviving documentation does not give the AU-D7 a confirmed production year, an original retail price, or a body of independent bench testing. The service manual exists and is thorough; the review coverage is not. Collectors chasing one should expect to verify voltage configuration, confirm the presence of the rack adaptors if the black model is the target, and budget for the usual recapping work on a unit of this vintage - particularly the large filter capacitors, which are the components most likely to have drifted. The MC phono stage is the headline feature. A 250-microvolt moving coil input on an integrated amplifier of this class was not a given.
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