Sansui AU-X1111 MOS Vintage (1988)
The AU-X1111 MOS Vintage is the final amplifier in Sansui's X series. The line began with the AU-X1 in 1979, continued through the AU-X11 and AU-X111 MOS Vintage, and ended here in 1988. It was Sansui's flagship integrated amplifier at launch, priced at ¥400,000 in Japan and 6,500 DM in Germany. It weighs 35.1 kg. The circuit is fully balanced and ground-free, a philosophy Sansui had been developing since its wide-range DC amplifier of 1976.
The engineering is distinctive. A conventional earth-based amplifier drives the speaker against ground, which Sansui argued made it susceptible to ground-borne noise and distortion. The AU-X1111 drives both the + and − sides of the speaker in double-push-pull under identical conditions. The power supply runs as a closed loop with no connection to the ground circuit, and no line filter sits in the signal path. The diamond power stage uses 16 MOS FETs, arranged in four double-push-pull positions on the left, right, + and − sides. The twin-monaural construction puts the large power transformer at the center, with the power amplifier sections on heat sinks symmetrically separated. The power MOS FETs, transformer, and master volume are mounted on a pure copper plate, and the bottom plate is copper-plated for shielding. The left and right volumes are completely independent.
The cosmetics are as ambitious as the circuit. The sides and top are real rosewood, there is a front glass panel, and Sansui called the lighting a “shower light.” The preamp and power sections can be separated from the front panel, and the power amplifier input levels are independent for left and right. A presence control slightly raises mid and low band energy at low listening volumes without changing tone.
Specifications are exceptional even by flagship standards: 110W + 110W into 8Ω and 150W + 150W into 6Ω (both channels driven, 10 Hz–20 kHz), with total harmonic distortion of 0.008%. Dynamic power reaches 320W into 2Ω. Frequency response extends from DC to 300 kHz (+0/−3dB) at 1W, slew rate is ±150 V/µs, and damping factor is rated at 200. Signal-to-noise is 115 dB or better (A-weighted) on the main inputs, and the phono MM stage manages 88 dB. Power consumption is rated at 350W (820W maximum). Dimensions are 470 × 178 × 486 mm.
Documentation beyond the factory specifications is thin. No independent period reviews in English-language publications have surfaced, and little is recorded about real-world ownership. What exists is positive. A Russian forum user reported that the AU-X111 MOS Vintage (the earlier 1985 model in the same series) sounded more interesting via balanced operation than another amplifier with temporarily wired balanced inputs, with a wider soundstage and higher dynamics. A seller on Avito offering the AU-X1111 MOS Vintage in excellent condition noted it was recently shipped from Japan. Asking prices on Russian listings ranged from 225,000 to 250,000 ₽. A repair and restoration service for the AU-X1 through AU-X1111 family exists on eBay.
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