Sansui AU-3900 (1976-1977)
At 8.5kg, it sits in your rack like a compact promise of vintage Japanese engineering—solid, no-nonsense, and ready to sing
Overview
The Sansui AU-3900 is an integrated stereo amplifier built in Japan between 1976 and 1977, part of a lineage that collectors quietly respect but rarely shout about. Measuring 420 x 140 x 305mm, it’s a mid-sized component by 1970s standards—neither imposing nor undersized, with a weight of 8.5kg suggesting substantial internal layout without the bulk of higher-end contemporaries. It shares core specifications with the more powerful AU-4900, including the same low distortion performance, though with slightly reduced power output. It was positioned alongside models like the AU-2900 in Sansui’s amplifier family, offering a balance of phono-stage capability and solid-state control.
Despite its modest footprint, the AU-3900 packs 27 transistors and 14 diodes, indicating a complex internal design for its time. It drives speaker loads between 4Ω and 16Ω, making it adaptable to a range of vintage cabinets. Input sensitivity is rated at 2.5mV for the MM phono stage and 150mV for line-level sources, with a phono input impedance of 50kΩ as confirmed by schematic documentation. Signal-to-noise ratio checks in at 70dB for MM and 80dB for line, while total harmonic distortion is specified at 0.5%—a figure that aligns with mid-tier high-fidelity expectations of the era. Frequency response spans the full 20Hz to 20kHz range, suggesting a design focused on accurate, if not particularly dynamic, reproduction.
Specifications
| Manufacturer | Sansui Electric Co., Ltd. |
| Model | AU-3900 |
| Type | Integrated Stereo Amplifier |
| Year of Production | 1976-1977 |
| Country of Manufacture | Japan |
| Power Output | 20 watts per channel into 8Ω (stereo) |
| Frequency Response | 20Hz to 20kHz |
| Total Harmonic Distortion | 0.5% |
| Input Sensitivity | 2.5mV (MM), 150mV (line) |
| Phono Input Impedance | 50kΩ |
| Signal to Noise Ratio | 70dB (MM), 80dB (line) |
| Speaker Load Impedance | 4Ω to 16Ω |
| Semiconductors | 27 x transistors, 14 x diodes |
| Dimensions (W x H x D) | 420 x 140 x 305mm |
| Weight | 8.5kg |
Historical Context
It shares a service manual with the AU-4900, suggesting close engineering kinship, and is noted to have the same core specifications and distortion characteristics as that model, albeit with slightly reduced power. It was part of a broader family that included the AU-2900, positioning Sansui to cover multiple price points with consistent design philosophy.
Collectibility & Value
Current market prices for the AU-3900 range from $250 to $400, depending on condition and region. Owners describe it as a "great bargain vintage integrated amp," though some note that on paper, "it's nothing special hahah." Common issues include 100Hz (or 120Hz) hum, plopping sounds caused by failed filter capacitors, and occasional "weird rattle" noises potentially linked to diode failure. Recap is widely regarded as a standard maintenance procedure, with recap kits available for approximately $65 CAD shipped. One listing notes the importance of replacing known problem transistors, particularly on the tone board, to restore full functionality. Despite its unassuming specs, one satisfied owner concluded, "Whoever ends up owning this amp should be very happy."
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Related Models
- Sansui PM C100 (Unknown)
- Sansui 6060 (1975-1977)
- Sansui 551 (1973-1975)
- Sansui AU 555 (1968-1971)
- Sansui CA 3000 (1974-1977)
- Akai AM-2850 (1975)
- Akai AP-206 (1975)
- Nakamichi BX-1 (1985)
- Acoustic Research research-ar-17 (1978)
- Acoustic Research AR-19 (1994)