The Sansui AU-9500: A Masterclass in Japanese Hi-Fi Engineering
In the golden era of Hi-Fi during the early 1970s, Sansui was at the height of its engineering powers. Amidst the flood of mass-market audio gear, the AU-9500 stood as a flagship integrated amplifier that exemplified Sansui’s dedication to pure sound reproduction, technical excellence, and uncompromising build quality. Introduced as the top-tier model in the AU series, the AU-9500 was designed not merely to compete—but to lead.
Sansui AU-9500: A Heavyweight in Vintage Hi-Fi
In the landscape of early 1970s Japanese audio engineering, the Sansui AU-9500 holds a firm reputation as a landmark amplifier—both literally and figuratively. Launched around 1972, it was built during Sansui’s most respected engineering phase, before the aesthetic shift of the late 1970s and the rise of black plastic-era receivers. To vintage Hi-Fi collectors and seasoned audiophiles, it stands today as a symbol of serious, unflinching design and sound performance.
Build Quality That Commands Respect
One of the most frequently praised aspects of the AU-9500 is its sheer physicality. At over 23 kg, it’s often likened to a tank. The power transformer alone weighs more than some entire modern amplifiers. Audiophiles note that even internal components—like the die-cast metal knobs, thick chassis plating, and extruded aluminum heatsinks—were engineered with a quality-first mindset. Many regard it as overbuilt by modern standards, and that’s precisely the charm.
Sound Signature: Controlled Muscle with Vintage Warmth
Forum users consistently describe the sound as tight, muscular, and detailed, with a hint of vintage warmth, especially in the midrange. It has excellent control over speakers, particularly in the low end, thanks to its well-regulated dual power supply design.
• Vocals and acoustic instruments are rendered with a natural body and texture.
• Bass is impactful without being bloated—something noted especially when paired with vintage JBLs, Altecs, or high-efficiency Japanese speakers like Coral or Diatone.
• Highs are clean, not overly bright, and roll off naturally—no harsh digital edge here.
Many audiophiles describe the AU-9500 as a “muscle amp with finesse,” able to deliver both raw power and tonal delicacy.
Technical Praise
The AU-9500 includes features well ahead of its time:
• Separate pre-out/main-in for pairing with external power amps.
• Switchable phono inputs, capable of handling both MM and lower output carts.
• Precise tone control section, with the option to defeat it entirely.
• DC-coupled design for broader frequency response and tighter bass.
Its distortion levels (THD: ≤ 0.1% ) and frequency response figures (5 Hz – 40,000 Hz full rated power bandwidth) matched or exceeded international standards of the day, earning praise in reviews from both Japanese magazines like Swing Journal and Western outlets.
Comparison to Other Sansui Legends
While many collectors prize later models like the AU-11000 or the AU-20000 for their specs and scale, the AU-9500 is often praised for having a more natural, musical presentation—especially at moderate listening levels in home setups.
Sansui AU-9500
Where Engineering Meets Elegance
When Sansui launched the AU-9500 in the early 1970s, they weren’t just releasing another integrated amplifier—they were crafting a reference-grade unit that embodied the philosophy of no-compromise audio reproduction. Every aspect of the AU-9500’s design—electrical, mechanical, and aesthetic—was developed with precision, guided by Sansui’s unwavering commitment to sonic excellence and reliability.
1. All-Stage Direct Coupling:
At the core of the AU-9500’s amplifier design is its all-stage direct-coupled circuit. Unlike conventional designs that use coupling capacitors between amplifier stages—often coloring the sound or limiting bandwidth—Sansui chose to eliminate these entirely. Instead, they implemented a fully direct-coupled OCL (Output Capacitor-Less) push-pull design, allowing for cleaner signal transfer, tighter bass response, and a more extended frequency range. The result was superior low-frequency clarity and higher transient accuracy, crucial for vinyl playback and wide-band analog sources.
2. Parallel Push-Pull Output Stage:
To ensure ample power and low distortion, Sansui employed a parallel push-pull output configuration. This design not only increased output current capacity but also improved linearity, especially under load. Rated at 80 watts per channel into 8 ohms (and conservatively so), the AU-9500 maintained control over speakers with poise and headroom, even at high volumes.
3. Dual Power Supply System:
The AU-9500 uses a dual power supply design with separate regulated rails for each channel, contributing to superior channel separation and reduced crosstalk. Additionally, the pre-driver stage operates at a higher voltage than the output stage—a rare design consideration—ensuring clean, unclipped voltage swing and high dynamic range.
The massive power supply filtering is anchored by four large 4,700µF capacitors (18,800µF total), which provide outstanding transient response and rock-solid stability, even when driving complex speaker loads or during dynamic musical passages.
4. Precision Phono Equalizer Circuit:
Sansui equipped the AU-9500 with a phono stage that rivals many standalone preamps. The three-stage phono equalizer uses low-noise, direct-coupled transistor circuitry to achieve superb RIAA accuracy (±0.5dB from 30 Hz to 15 kHz). The high overload margin (up to 300 mV) and separate regulated power supply ensure precise, distortion-free playback for both MM and high-output cartridges.
Additionally, Phono 2 input features switchable loading resistors (30kΩ/50kΩ/100kΩ) to allow for proper cartridge matching—an audiophile feature still prized today.
5. Triple Tone Control System (T.T.C.):
Unlike most integrated amps with fixed tone circuits, the AU-9500 introduced a Triple Tone Control system, giving users real-time control over bass, midrange, and treble. Each band features three selectable turnover frequencies, allowing precise tailoring of tonal balance without sacrificing musicality. Importantly, each control has a defeat switch for purist listening, bypassing the tone circuitry entirely.
This flexibility made the AU-9500 not just an amp, but a studio-grade tool—ideal for systems needing room correction or adjustment to various musical genres.
6. Full Preamp/Main Separation:
The AU-9500 offers a Pre Out / Main In loop with dedicated jumpers, allowing users to insert external processing (like an equalizer or crossover) or use the AU-9500 as a standalone preamp or power amplifier. This design ensured adaptability across different system configurations—a rare feature at the time, and invaluable for today’s vintage collectors seeking flexibility.
7. Protective Circuitry with Audio Relay:
Sansui included a fast-action speaker protection relay, which mutes output during power-up and guards against DC offset and overcurrent conditions. Combined with internal fuses and thermally linked sensors, the AU-9500 was designed to protect both itself and your valuable loudspeakers—a thoughtful nod to long-term reliability.
8. Extensive Connectivity and Switching:
This amplifier was built for serious system integration. It provides:
• Two phono inputs
• Two AUX inputs
• Dual tape monitor loops
• Microphone inputs (with mix control)
• Dual speaker outputs (A/B/C)
• Independent recording and monitoring switching
Volume, balance, loudness, filters (high and low), and input sensitivity adjustments round out the control panel—giving the listener unprecedented command over their listening environment.
9. Construction and Aesthetics:
The AU-9500’s design was not only functional but visually elegant. The brushed aluminum front panel, solid machined knobs, toggle switches, and engraved labeling exude a timeless quality. Internally, the layout is clean, symmetrical, and overbuilt—military-grade in many respects. Every component and solder joint reflects Japanese manufacturing at its peak.
The chassis is shielded to minimize hum and magnetic interference, while the vented top cover ensures adequate thermal dissipation without reliance on noisy fans.