Sansui AU-717
A DC integrated amplifier that Sansui's own advertising dared the rest of the industry to measure against. For a few years in the late 1970s, plenty of buyers took them up on it.
Overview
The AU-717 arrived as the larger half of a two-model launch. It shared its chassis language and DC-coupled topology with the AU-517, and Sansui's literature paired it with the matching TU-717 tuner. The two amplifiers differ in output stage capacity, not architecture. The 717 carries four 15,000µF 63V filter capacitors and a pair of power transformers (one per channel, with separate part numbers for the XX, EU/BS, and UL/CSA markets). The 517 makes do with less. That dual-mono power supply is why the 717 has always commanded a premium over its smaller sibling on the used market, and it's the first thing a technician notices when the bonnet comes off.
The headline number, per period coverage, is 85 watts per channel into 8 ohms with total harmonic distortion held to no more than 0.025%. HI-Fi-Stereo-Buyers (September 1978, p.43) listed the amplifier at $550 with full monitoring and dubbing facilities for two tape decks. That suits an enthusiast with a cassette deck and a reel-to-reel both patched in. The 85-watt figure is not enormous by late-'70s standards. The distortion spec is the interesting part: 0.025% THD at rated output was a genuine engineering claim in 1977, not a marketing rounding exercise.
Sansui's own advertising in this period was unusually combative. A 1977 campaign placed the AU-717, AU-517, and TU-717 as "the standards of excellence against which all other integrated amps and tuners will be measured," and a separate Audio (February 1978, p.9) insertion went further, describing the AU-717 as a DC integrated amplifier with a calibrated-attenuator level control that "guarantees volume precision." The design choices behind the claims are real and documented in the service literature.
The front panel is where the 717's ambitions become visible. Two rotary switches handle speaker selection and tape copy, a third selects input; the tone section runs on a dedicated F-2720 board with a 250kΩ (MN) dual balance pot and a 100kΩ dual pot for treble and bass. There is a tone defeat switch, a muting switch, a subsonic filter, and a high filter — the full late-'70s control complement, laid out with lever switches rather than the pushbuttons that would dominate the following decade. A headphone jack sits on the front panel, and the turnover switch lives on its own small F-2666 board, which tells you how seriously Sansui took the phono section.
That phono stage is a two-board affair. The F-2723 equalizer board carries a complement of 2SA906, 2SA726, 2SC1400, and 2SA750 transistors arranged in differential pairs, with VD1212 varistors for bias stability and a mix of polystyrene and mylar capacitors in the RIAA network. High Fidelity (October 1977, p.12) noted that equalization was held within ±0.2dB across 20Hz–20,000Hz on the extended RIAA curve — a figure that mattered to anyone running a moving-magnet cartridge with a modest output, because it meant the correction network wasn't adding its own coloration on top of the record's.
The driver boards are the F-2721 (left) and F-2722 (right), and they are not interchangeable. Keep that in mind before a repair. Output devices are 2SC1116 and 2SA747 pairs, and the main filter capacitors are the four 15,000µF 63V cans mentioned earlier. Fusing varies by market: 5A 125V for the XX version, 10A 250V for AA, and 3.15A for EU/BS. Buyers importing a Japanese-market unit should check which transformer and fuse complement they actually have before plugging it into a 120V wall.
High Fidelity (October 1977, p.12) also weighed in on the sound itself, describing the AU-717 and AU-517 as having a frequency response distinctly wider than other amplifiers then available, with what the reviewer characterized as spacious stereo perspective, strong musical presence, and low distortion. That is advertising-adjacent language in places, but the measurement claims behind it are specific enough to be checkable, and the review ran in a publication with a reputation for actually putting gear on the bench.
The 717 is not a powerhouse. At 85 watts per channel it sits below the flagship integrateds of the era, and anyone driving low-sensitivity acoustic-suspension speakers at party levels will find the limits. What it offers is a clean, well-regulated 85 watts from a dual-transformer supply, a phono stage and a control set that covers two tape decks without an outboard switching box. With efficient speakers in a normal room, that is a more useful combination than another 50 watts of headroom.
The service documentation is unusually complete for a consumer amplifier of this vintage. The AU-517/717 manual includes full parts lists for the tone control board (F-2720), equalizer board (F-2723), turnover switch board (F-2666), and driver boards (F-2721/F-2722), with stock numbers for every transistor, capacitor, and resistor. That matters enormously in 2026, because it means a technician can identify and source replacements for the 2SA798 dual transistors and VD1212 varistors that are the usual failure points in amplifiers of this age, rather than reverse-engineering the circuit from photographs.
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