The Sansui AU-666 is a mid-tier integrated amplifier from Sansui’s classic early-1970s lineup, known for its warm, natural, and highly musical sound. Sitting between the AU-555A and the AU-888, the AU-666 strikes the perfect balance of refinement, power, and value.
Built with Sansui’s hallmark attention to detail, the AU-666 features a robust all-metal chassis, solid aluminum front panel, and well-laid-out controls that remain smooth and precise even after decades. Inside, Sansui employed carefully selected Japanese components and low-noise circuitry that delivers a clean yet engaging sound signature—warm, rich in the midrange, and detailed without being fatiguing.
Often praised by enthusiasts for its ability to bring out the natural timbre of vocals and acoustic instruments, the AU-666 pairs beautifully with efficient vintage speakers, offering a sound presentation that is dynamic yet smooth. With 35 watts per channel into 8 ohms, it has enough drive for most home listening setups, while maintaining Sansui’s signature tonal balance that makes long listening sessions a joy.
Perfectly matches with high-efficiency 8 Ω speakers like the Klipsch Heresy or JBL L-100, delivering impressive volume and clarity even in modest listening space
Sansui AU-666
The Sansui AU-666 stands out for its innovative and thoughtful design, blending audio performance with reliability and distinctive features. Its structure reflects Sansui’s commitment to both sound quality and technical durability.
Circuit and Sound Design
- Utilizes a direct-coupled, complimentary Darlington output stage (no output capacitor), ensuring wide frequency response, lower distortion, and consistent damping factor throughout the audio range.
- Employs two-stage differential amplifier circuits and both PNP and NPN transistors, which cancel distortion components and enhance fidelity.
- Features uniform negative feedback (NF) application across the entire frequency range, improving stability and accuracy.
- The preamp section includes low-noise silicon transistors to minimize hiss and background noise.
- Uses high-quality Mylar capacitors in critical signal paths instead of electrolytic types, greatly improving high-frequency and phase accuracy.
Controls and Flexibility
- Equipped with triple tone controls: separate adjustment for bass, midrange, and treble, with individual left/right channel controls for precise room and program compensation.
- Facilitates separation of preamp and power amp sections for integration into complex systems or use with external components.
- Dual speaker outputs (A and B) and muting switch add practical functionality for varied listening setups.
Protection and Build Quality
- Features a dedicated transistor for thermal stability and a differential amp stabilizer to maintain performance during temperature shifts.
- Integrates six short-cut fuses, providing robust protection in case of faults or overloads.
- Separate ripple filter circuits for each power supply section stabilize voltage and enhance sonic performance.
- Classic physical build: solid knobs, durable chassis, and a signature wood/black fascia deliver both tactile quality and visual appeal.
User-Oriented Additions
- Additional features include NF-type low and high filters, loudness control, tape monitor, headphone jack, muting, and a microphone input, making the AU-666 highly versatile for its era.
- Thoughtful ergonomics ensure long-term reliability and ease of maintenance, with high-quality parts used throughout.
The Sansui AU-666 is widely recognized for combining audiophile-grade architecture with user-centric design, earning acclaim for both its sonic and physical engineering.