Sansui’s Esteemed AU/TU Series: Engineering Excellence Meets User Focus
For over a decade in the 70s/80s, Sansui’s AU/TU line of integrated amplifiers and tuners occupied a special place in the hearts of audiophiles. Lauded by the company as receiving the highest praise and cultivating one of the most devoted followings of any component series in their history, the AU/TU designation has consistently signified more than just hardware; it has represented a commitment to incorporating the latest technical advancements alongside thoughtful user conveniences and design innovations of the day.
With the Professional Series, Sansui unveiled the latest generation destined to carry this prestigious banner. Positioned as the most powerful, accurate, and dependable components yet in the lineage, these new models aim to embody Sansui’s renowned tonal quality standards at the highest level. A standout example, the AU-20000 integrated amplifier, showcases the engineering philosophy driving this evolution.
Under the Hood: Power and Precision
At the core of the AU-20000 lies a formidable amplification stage. Each channel employs a robust triple push-pull output circuit, utilizing no fewer than six hand-selected power transistors. This design ensures ample power reserves, guaranteeing the delivery of rated output with minimal distortion, even during demanding musical passages.
Supporting this powerhouse is a meticulously engineered power supply designed for unwavering stability and dependability. It features a plus-minus symmetrical voltage configuration, centered around a low-leakage toroidal transformer coupled with generously sized capacitors. This foundation provides the clean, stable current necessary for optimal performance across the dynamic range.
Refining the Signal Path
Sansui paid particular attention to the critical phono stage. The AU-20000 employs an 8-transistor equalizer design featuring differential amplifiers at the initial stages to enhance dynamic response and minimize noise. A sophisticated dual-amplifier approach – using CR-type (Capacitor/Resistor) equalization for high frequencies and Negative Feedback (NF)-type for lows – achieves highly accurate RIAA curve reproduction, crucial for faithful vinyl playback. Furthermore, selectable phono sensitivity and impedance (each with three settings) allow users to perfectly match the amplifier to virtually any phono cartridge, optimizing performance.
For tonal shaping, the amplifier incorporates Sansui’s exclusive Triple Tone Control system. Governed by a CR-type circuit and benefiting from the plus-minus voltage supply, this feature offers nuanced control over bass, midrange, and treble frequencies while maintaining excellent transient response and dynamic range.
Connectivity, Control, and Protection
Acknowledging the needs of serious enthusiasts, the AU-20000 boasts versatile tape handling capabilities. It accommodates up to three stereo tape decks, facilitating individual monitoring and deck-to-deck dubbing, even allowing source monitoring during the copying process.
Comprehensive protection systems are integrated to safeguard the amplifier and connected speakers. A trio of circuits continuously monitors for temperature irregularities, DC voltage leaks at the output, and unsafe operating conditions (ASO detection). Should a fault like shorted speaker terminals occur, these circuits instantly react to prevent damage.
Rounding out the user experience are thoughtful conveniences like a Tone Defeat switch for bypassing tonal adjustments, a 3-step audio muting switch, switchable low and high filters, a mode selector, and a sensitivity switch for the large, self-illuminated VU meters that dominate the front panel, providing clear visual feedback on output levels.
In essence, this series of additions to the AU/TU series, exemplified by the feature-rich AU-20000, underscored Sansui’s enduring effort to blend cutting-edge audio engineering with practical, user-focused design, continuing their legacy cherished by audio enthusiasts worldwide.