Sansui AU-9900
This newly restored Sansui AU-9900 (Japan Domestic Model at 100V) is a flagship integrated amplifier from Sansui’s golden era, delivering 80W per channel of pure, dynamic power. Built with a true dual-mono layout and advanced OCL circuitry, it offers exceptional clarity, detail, and musical warmth. Its precision 3-band tone controls, selectable turnover frequencies, and low/high filters give you total control over your sound.
Crafted for both versatility and sonic purity, the AU-9900’s preamp and power amp sections can be separated, making it a perfect match for various system configurations. Solidly built at 17.6kg, it embodies Sansui’s hallmark engineering and timeless design—a true collector’s piece for those seeking vintage Japanese HiFi excellence.
This vintage Sansui AU-9900 has been meticulously cleaned and fully restored inside and out by our Takumi (master craftsmen). Following a complete overhaul, it is now ready to be the masterpiece of your HiFi system.
The Sansui AU-9900 represents the peak of Sansui’s mid-70s integrated amplifier engineering, combining meticulous circuit design with robust mechanical construction. Every element was built with the dual goals of sonic purity and long-term reliability.
Chassis & Layout
- True Dual-Mono Construction – Left and right channels are electrically and physically separated from the transformer stage onwards. This dramatically reduces crosstalk and improves stereo imaging.
- Rigid Steel Frame – Heavy-gauge steel chassis with reinforced frame to eliminate vibration-induced noise.
- Logical Internal Layout – Signal path is kept short, with inputs and controls arranged for optimal flow and minimal interference.
- Side-Mounted Speaker Terminals – Designed for cleaner rear cable management and better separation from AC mains wiring.
Amplification & Circuitry
- OCL (Output Capacitor-Less) Design – Delivers tighter bass, greater damping factor, and more natural transient response.
- Differential Amplifier Input Stage – Improves linearity and reduces noise floor for high-resolution signal reproduction.
- Parallel Push-Pull Output Stage – Uses matched transistor pairs to provide stable high-current delivery under complex loads.
- High-Grade Components – Precision resistors, low-noise transistors, and Sansui-spec electrolytic capacitors for consistent tonal balance.
Controls & User Interface
- Three-Band Tone Controls – Separate bass, midrange, and treble adjustments with selectable turnover frequencies for precise tonal shaping without excessive phase shift.
- Filter Options – Low (subsonic) and high filters to reduce unwanted rumble and hiss from vinyl and tape sources.
- Loudness Compensation – Maintains perceived tonal balance at low listening volumes.
- Muting & Attenuation – Adjustable muting to quickly drop output levels without powering down.
- Dual Tape Loops – Independent tape monitor circuits for recording and dubbing flexibility.
Connectivity & Flexibility
- Separable Preamp & Power Amp Sections – External processors or upgraded power stages can be added via Pre-Out / Main-In jumpers.
- Multiple Speaker Outputs – Switchable A/B speaker pairs with independent impedance handling.
- Phono Stage – Precision MM phono preamp with high overload margin, designed for low-noise vinyl playback.
- Multiple Line Inputs – Supports tuner, auxiliary, and two tape decks for system versatility.
Build Quality & Serviceability
- Oversized Power Supply – Large EI-core transformer and dual filter capacitors for stable power under demanding loads.
- Robust Heat Dissipation – Large aluminium heat sinks ensure safe operation over extended sessions.
- Service-Friendly Design – Modular internal boards for easier access during maintenance and restoration.
Power / Performance:
- Rated output (both channels driven): 80 W + 80 W (into 8 Ω; also quoted for 4 Ω).
- Total Harmonic Distortion (rated output): ≤ 0.08 % (typical spec; some measurements show 0.05% at 1 kHz/1 W).
- Frequency response: 10 Hz – 50 kHz (+0 / −1 dB measured at 1 W).
- Damping factor: ≈ 80 (measured at 8 Ω).
Noise / Separation / Distortion:
- Signal‑to‑Noise Ratio (S/N): ≈ 65 dB (MM phono), ≈ 80–90 dB (line) depending on source/version.
- Channel separation: ~55 dB (phono), ~60 dB (line).
- RIAA deviation (phono): ±0.3 dB (30 Hz–15 kHz).
Inputs / Sensitivities:
- Phono (MM) input sensitivity: 2 mV for rated output.
- Line / DIN input sensitivity: ~130 mV.
- Pre‑out voltage: ~0.7 V.
Load / Connectivity:
- Speaker load impedance: 4 Ω – 8 Ω (switchable A/B speakers supported).
- Tape loops: Dual tape monitor loops (two tape circuits).
- Separable preamp / power amp (Pre‑Out / Main‑In jumpers) for use as separate units.
Tone / Controls / Features:
- Three‑band tone control (Bass / Mid / Treble) with selectable turnover frequencies (useful mid‑range shaping).
- Low and High filters (subsonic / high frequency cut), loudness compensation, muting and attenuation functions.
- Built with OCL (Output‑Capacitor‑Less) topology, differential input stage, and parallel push‑pull output transistors.
Power Supply & Mechanical:
- Large, well‑regulated power supply with substantial filter capacitors and substantial heat‑sinking.
- Chassis layout: preamp/tone controls front side; power section, heat sinks and power transformer rear side (partitioned layout to reduce interference).
Physical:
- Dimensions: approx. 460 × 150–160 × 373–407 mm (varies slightly by source/version).
- Weight: ≈ 17.6–17.9 kg (depending on regional variants).
Sound Signature
Renowned for its warm yet detailed presentation, the AU-9900 offers a soundstage that’s both wide and deep, with lifelike instrument separation. Bass is full and controlled, mids are rich and textured, and treble is smooth without losing sparkle. This amp has the speed and dynamic headroom to handle complex music—from the punch of classic rock to the subtleties of jazz—while retaining the musical “flow” vintage Sansui is known for.
What Fans Are Saying?
• “Musical, Pleasant & Non-Fatiguing”
“The Sansui is many times better… It’s much more musical and tremendously pleasant to listen to… Warmth and richness… what it lacks in detail it makes up for in robustness.” - stevehoffman.tv
• “Warm, Room-Filling, and Never Fatiguing”
“It’s a Neutral, underrated kit… The Sansui has got a very warm sound, capable of playing it loud to fill the room without being fat or flabby.” - HiFi4Sale
• “Crisp & Accurate; Great with Contemporary Music”
Contrast with other models:
“…the 9500 is best for jazz, blues and the 9900 is more crisp and accurate for more contemporary music.” - Audiokarma
• “Speed & Micro-dynamics for Modern Genres”
“9900 has higher damping factor… if you listen heavy-metal, electronics or synth-pop choose 9900. It is more faster with more micro-dynamics.” - vinylengine.com
• Foundations for Clean, Tight Bass
With tone controls bypassed, “as I turn it up… the bass is more than adequate… nice and tight, not boomy.” - Audiokarma
This vintage Sansui AU-9900 has been meticulously cleaned and restored, both inside and out, by our Takumi (Master Craftsmen), who carried out a complete overhaul.
Since its return, it has been put through 3 weeks of testing by us at Vintage Japan HiFi. The results? It sounds as powerful and clear, truly exceptional for a piece of its era.
Condition Overview:
- Cosmetic Condition: 9.5/10 – Mint condition ! One of the finest examples that we have seen so far.
- The front, back, side and top panels are all in very clean condition without visible scratches. Performance: 9.5/10 – Operating at peak specifications with amazing sound clarity and depth.
Note:
Our overhaul service focuses on preserving the original sonic character of the amplifier. We only replace non-functioning electronic parts, ensuring each piece remains true to its factory specifications. Unlike the common practice in many US HiFi workshops, where all capacitors, transistors, and other components are replaced, our ex-Sansui engineers and technicians advise against this, as it changes the amplifier’s authentic sound profile. We honour this approach to maintenance and restoration. However, if you’re looking for more extensive "recapping," feel free to reach out by email for a personalized service quote.
All control knobs and switches have been professionally cleaned and lubricated. However, scratchy noise cannot always be completely eliminated and may reappear over time. This is an unavoidable characteristic of vintage Hi-Fi equipment due to age and component wear. It should not be considered a defect, but rather a natural sign of the unit’s history and originality.
Please refer to our disclaimer notes for further details.
If this occurs, gently rotate the relevant control knobs (volume, or balance) back and forth several times before use. In many cases, this will significantly reduce or temporarily eliminate the noise.
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For any vintage audio hifi equipment:
Please be aware that, given this vintage hifi equipment's age, certain switches and original parts are no longer in production. While we’ve thoroughly cleaned and lubricated any “gari gari” scratchy controls (as they’re called in Japan), it’s simply not possible to eliminate this characteristic entirely since volume knobs and switches cannot be disassembled.
We recommend regular servicing every 2 to 3 years, depending on the equipment, to keep this vintage hifi in peak condition. This advice applies to all vintage equipment—be cautious of sellers who claim "brand-new condition" or “better than original.”
Minor scratchy sounds in control knobs are typical for vintage gear and should not be seen as a defect but rather a natural sign of its history since it does not affect the actual performance or introduce noise into the audio signal source unless being operated.
If this occurs, gently rotate the relevant control knobs (volume, or balance) back and forth several times before use. In many cases, this will significantly reduce or temporarily eliminate the noise.
For optimal sound quality, we advise pairing this amplifier with high sensitivity speakers (88-92 db). If you need guidance on amplifier matching, feel free to reach out for assistance.