Sansui AU-9500 (1972–1975)

At 22.5 kg, it lands on the rack hard. This is not an amplifier for the timid.

Overview

The Sansui AU-9500 is the top-of-the-line pre-main amplifier Sansui built with the best circuit technology of its day. It was assembled from selected parts with a no-compromise philosophy. It was released in October 1972, and production continued through roughly 1975. Owners report a machine that feels overbuilt the moment they lift it, with the kind of heft that points to serious internal components and careful assembly.

The AU-9500 uses an all-stage direct-coupled pure complementary circuit. It is an OCL (output capacitor-less) design, so there are no coupling capacitors in the signal path. The result is unusually direct transient response and phase coherence for an integrated amplifier of the period. A parallel push-pull output stage, dual-mono power supply architecture, and a +/− 2 supply system that feeds the power stage and pre-drive stage from separate rails all add to a stability and headroom that separates-class gear usually claims for itself. Owners describe the sound as clean and effortless, especially at high volumes, and the amp is frequently called one of the finest vintage integrateds around. High Fidelity (March 1974, p.121) walked readers through its control-amplifier section. It noted the unit could handle two phonographs, a microphone, a tuner, and an auxiliary input, with channel-reverse and per-channel mono capability. That versatility was unusual for the class.

The front panel is clean and almost austere, with pure aluminum knobs across the board. Behind it, the semiconductor count runs to 48 transistors, 4 ICs, 4 FETs, and 32 diodes. It is a dense, discrete design, not an op-amp shortcut.

Key Features

All-Stage Direct-Coupled OCL Pure Complementary Circuit

Every stage of the AU-9500 is direct-coupled, with no output capacitor in the signal path. The parallel push-pull output stage lets each power transistor run at roughly half the collector current it would otherwise need. That keeps the devices in the region of their current-amplification curve where linearity is best. Rated total harmonic distortion is not more than 0.1% at rated output, with cross-modulation distortion held to 0.1% or less on the SMPTE standard (70 Hz : 7 kHz = 4 : 1).

Dual-Mono Power Supply with +/− 2 Rails

The AU-9500 uses a +/− 2 power supply system with separate supplies for the power stage and the pre-drive stage. The pre-drive stage runs at a higher voltage than the output stage. A large power transformer feeds four 4,700 µF capacitors, and the whole amplifier draws 280 W. This architecture is one reason the amp can sustain 75W + 75W continuously into 8 Ω from 20 Hz to 20 kHz without strain, and why its damping factor is specified at 50 into 8 Ω.

Triple Tone Control (T.T.C.) with Selectable Turnovers

Sansui's T.T.C. system is one of the amp's signature features. The bass control offers a defeat position plus selectable turnover frequencies at 150 Hz, 300 Hz, and 600 Hz, adjustable ±15 dB at 20 Hz in 3 dB steps. The midrange control centers on 750 Hz, 1.5 kHz, or 3 kHz, adjustable ±5 dB in 1 dB steps. The T.T.C. amplifier itself uses a low-noise FET in the first stage for high input impedance, with NF-type three-stage and two-stage direct-coupled circuits behind it. Few integrated amplifiers of the era matched this level of control.

3-Stage PNP-NPN-PNP Direct-Coupled Phono Equalizer

The phono stage is a three-stage direct-coupled equalizer built from PNP-NPN-PNP transistor pairs, with RIAA deviation guaranteed to ±0.5 dB from 30 Hz to 15 kHz. Phono 1 is fixed at 50 kΩ input impedance. Phono 2 has a rear-panel switch for 30 kΩ, 50 kΩ, or 100 kΩ, so moving-magnet cartridges with different electrical requirements can be matched properly. Maximum allowable phono input is 300 mV with distortion held below 0.5%, which makes the stage resilient to overload. Crosstalk at rated output (1 kHz) is 50 dB or better on both phono inputs.

12 dB/oct NF-Type Active Filter System

The AU-9500 includes a dedicated 12 dB/oct NF-type active filter circuit. The high filter switches between 12 kHz and 6 kHz. The low filter switches between 25 Hz and 50 Hz. They are useful for taming tape hiss on bright sources or rolling off rumble and port noise from speakers, and they integrate cleanly with the rest of the tone-control section.

Three Speaker Systems with A+B / A+C Switching

The rear panel has speaker jacks for three pairs labeled A, B, and C, with a front-panel switch selecting between A+B and A+C. Each pair should be 8-16 Ω when run in combination, or 4-16 Ω when run alone. That allows multi-room setups or A/B comparisons, though driving multiple pairs at once pushes the amp's thermal limits.

Independent Preamp and Main Amp Operation

With the connectors on the rear panel removed, the preamplifier and main amplifier sections can be used independently. The AU-9500 becomes either a standalone preamp or a standalone power amp. It is a separates-grade feature.

20 dB Muting Switch

A front-panel muting switch attenuates the entire signal path by 20 dB without touching the volume knob. It is handy for quick interruptions, and it saves wear on the volume potentiometer.

Two Headphone Jacks with Auto-Speaker Cut-Off

Two headphone jacks sit on the front panel, and one of them automatically cuts off the speaker output when a plug is inserted. That prevents accidental bursts of sound through the speakers during private listening, which matters given the amp's low noise floor.

Two Tape Decks with Tape-to-Tape Reprint

The AU-9500 supports two tape decks with full monitoring and recording. The tape reprint switch lets owners dub directly between decks in either direction or record from the selected source. Both PIN and DIN connectors are provided, including a special 5-pin DIN for Tape Deck 2. Deck 1, Deck 2, and AUX each have level adjusters so input levels can be unified.

Protection Circuitry and Relay Muting

A relay combined with an electronic circuit and a quick-acting fuse protects the power transistors and speakers in the event of a fault. A current limiter circuit caps collector current in the output and driver stages. The relay also works as an audio mute, so there is no pop when the power is switched on.

Mode Selector, Loudness, and AC Outlets

A 5-position mode selector covers Stereo Reverse, Normal, Mono, L+R, and L/R. A loudness circuit is onboard, along with two grounding terminals and four AC outlets, two switched and two unswitched, for powering tuners, tape decks, or turntables from the back of the amp.

Historical Context

The AU-9500 was the top of the line model when Sansui's founder and perfectionist, Mr. Kosaku Kikuchi, retired in 1974, and it has been written that the amplifier satisfied his highest expectations. His product philosophy was "Let the products speak themselves." Original Japanese pricing was ¥135,000 at release in October 1972, which placed it firmly at the top of Sansui's integrated lineup.

The matched TU-9500 tuner was built as its companion, and period advertising presented the pair as a partnership rather than two separate components. Audio (November 1973, p.31) listed the AU-9500 at $519.95 in a lineup that also included the AU-7500 at $299.95 and the AU-6500 at $249.95, which put the flagship well above its siblings. A contemporary review noted that while several 100-plus-watt integrated amplifiers existed, none matched the AU-9500's feature set. The original release date places it in the transition period when Japanese audio brands were beginning to dominate high-end stereo systems worldwide.

Collectibility & Value

The AU-9500 has a cult following among vintage audio enthusiasts and is today frequently described as one of the most sought-after integrated amplifiers among audiophile collectors. No official production numbers or widespread market data exist, but recent listings give a reasonable picture. StereoNET reports a fair Australian market price of roughly AUD 1,500-2,200 for good-to-excellent examples, and a Canuck Audio Mart listing from June 2025 asked CA$1,680. Dealer listings in the US have asked $1,499 (with a discounted current price of $1,320 at one shop), and a matched AU-9500 and TU-9500 pair has been listed with a "New Price" of $1,395. An eBay listing based on the AU-9500 and QRX 9001 power amplifier was asking $850.

Common service issues center on transistor failures, particularly the 2SC983 types, and burnt resistors in the output stage, which often require a full recapping and bias adjustment. Owners note that RIAA equalization errors can occur if the phono stage is not properly calibrated, so a service manual and test equipment are essential before restoration. The amp's density and discrete design make it a satisfying but demanding restoration project.

eBay Listings

Sansui AU 9500 vintage audio equipment - eBay listing photo 1

Based on Sansui AU 9500 and QRX 9001 power amplifier 100V DI

$850

See all Sansui AU 9500 on eBay

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