Sansui AU-777D
This legendary Sansui AU-777D, is a Pre-Main amplifier from the Japan Domestic Market model at 100V. The preamp section and main amplifier section can be separated and used independently.
The AU-777D, in its upgraded form (from the best selling AU-777), is a vintage solid-state integrated amplifier that retains the original circuit configuration but focuses on improving sound quality and overall performance.
This amplifier is highly rated among audiophiles for its exceptional sound quality.
The AU-777D is another proud example of our curated work at VintageJapanHiFi. This amplifier has been meticulously cleaned and fully restored - nside and out - by our Takumi (Craft Masters from ex-Sansui company), who conducted a complete overhaul right here in Japan. It truly doesn't get any better than this.
The main amplifier utilizes a semi-complementary Darlington circuit, which enhances power efficiency and reduces distortion. The entire signal path, from the first stage to the output, is made up of negative feedback (NF) amplifiers, improving frequency response, lowering distortion, and increasing the signal-to-noise ratio for a cleaner, more accurate sound.
One of the key upgrades is the inclusion of a triple tone control system, which adds midrange adjustment alongside the traditional bass and treble controls, allowing for more precise sound shaping. To help with balance adjustments, the amplifier features a stereo balance check circuit, which simplifies the process of fine-tuning left and right channels. The PSC circuit offers protection for the power transistors, preventing damage from output short circuits, while the inclusion of a fast-off fuse further safeguards the components.
The amplifier also offers a center channel output, allowing for a more immersive 3D stereo experience when paired with a mono amplifier and subwoofer. The improved heat dissipation through a 3mm aluminium extension back panel ensures the amplifier can run continuously without overheating. Other features like low and high filters, a loudness control, tape monitor circuit, and a headphone jack add versatility, making the amplifier suitable for a variety of listening preferences and setups.
Overall, this upgraded Sansui AU-777 offers improved sound clarity, enhanced reliability, and more customization options, making it an appealing choice for both audiophiles and collectors who seek high-quality vintage audio equipment with modern features.
Sound Quality and Practical Considerations:
With all these upgrades, the amplifier’s sound quality would likely be significantly improved over the original AU-777. The focus on accuracy and refinement across multiple stages (input, amplification, output) would result in a more transparent and detailed listening experience. The upgraded tone controls and protection circuits also ensure that it’s not only better in sound but also more practical and reliable for everyday use.
The inclusion of center channel output and the ability to add a subwoofer means it would fit well into setups designed for stereo expansion, especially for audiophiles interested in multi-channel stereo systems or those looking to build a more immersive home theater experience.
Below is a summary of its key specifications and performance metrics:
Main Amplifier Section:
- Rated Output Power: 30W per channel at 8Ω (effective output), with music power rated at 70W (IHF) for dynamic performance.
- Total Harmonic Distortion: 0.5% or less, ensuring a clean and accurate output.
- Frequency Response: Extremely wide, spanning from 20Hz to 100,000Hz ±1dB, ensuring that the full range of audio frequencies are captured.
- Channel Separation: 20dB or more at 1kHz, which minimizes crosstalk between channels for a clear stereo image.
- Signal-to-Noise Ratio (S/N): 100dB or more (IHF), meaning the amplifier produces minimal background noise.
- Damping Factor: 15 (at 8Ω), contributing to better control over speaker drivers and tighter bass response.
Preamp Section:
- Output Voltage: Capable of a maximum output voltage of 4V, with a rated output voltage of 1V.
- Total Harmonic Distortion: 0.1% at rated output, maintaining a high level of clarity in the preamp section.
- Frequency Response: 20Hz to 70,000Hz (+0.5 -1.5dB), covering a wide frequency range for optimal detail and clarity.
- Signal-to-Noise Ratio (S/N): Phono1 and Phono2 have 80dB or more, ensuring minimal hiss or hum in quieter passages.
- Input Sensitivity/Impedance: Includes a wide variety of input options such as phono (2mV), MIC (3.5mV), Tuner (140mV), AUX (140mV), with different impedance ratings depending on the input type.
Tone Controls and Filters:
- Tone Control: The bass, midrange, and treble controls offer wide adjustment ranges, allowing for precise sound customization.
- Bass: ±15dB at 20Hz
- Midrange: ±5dB at 1,500Hz
- Treble: ±15dB at 20,000Hz
- Loudness Control: Boosts bass and treble at low volumes for a more natural listening experience at low listening levels.
- Filters: High and low-pass filters (20Hz to 20kHz) help shape the sound, especially for filtering out unwanted frequencies.
General Features:
- Power Supply: Designed for 100V at 50/60Hz, common in Japan.
- Dimensions and Weight: Compact yet solid, measuring 435mm wide x 155mm high x 334mm deep and weighing 12.5kg, ensuring a durable, high-quality build.
- Walnut Wood Case: The optional walnut wood case adds aesthetic value, with a separate cost of ¥4,150.
Center Channel Output:
- Includes both flat and high-cut (159Hz) output options, allowing for flexible integration with additional audio components like subwoofers or mono amplifiers for a more dynamic stereo setup.
Original (Japanese)
サンスイ AU-777D
Posted on 1969年11月20日
菅野沖彦
スイングジャーナル 12月号（1969年11月発行）
「SJ選定新製品試聴記」よりＡＵ７７７Ｄは、従来のＡＵ７７７を改良した新機種で、信頼度の高い、高いグレードをもったアンプである。ＡＵ７７７はベスト・セラーと呼ばれた製品で、サンスイのトランジスタ・アンプの評価を固めたアンプだが、このＤ型になって、一段と音楽的にもよくなった。試聴してみても、従来、やや気になった高音域のザラザラした荒さが大きく改良されていて、より滑らかにふっくらとした音を出すようになった。そして、中音域のバンド・パス・パターンをコントロールできるトリプル・トーン・コントロール方式の採用は、ルーム・アコースティックの調整に役立つのみならず、ジャズの再生にもっとも充実性を要求される中音域のコントロールに大きな威力を発確するものだ。一般に、迫力ある音にするというと、低音と高音を増強するような傾向がなきにしもあらずだがこれは本来正しくない。低高音を増強することは、中高域をやせさせることになり、決して迫力のある音にはならず、うるさい音になる。かといって、低、高音を落して中音域をクローズ・アップさせたのでは、切角のワイドレンジが泣く。この辺の微妙なコントロールは音づくりの妙味であるが、そう簡単にはいかないものだ。このトリプル・コントロールは中音域を１デシベル・ステップで、＋−５db調整できるようになっているが、これが大変上手い特性曲線に設定されていて効果的であった。決して極端な増減ではないし、選択帯域を曲線が適切で、あらゆるレコードに、まともな効果をあげることができるのである。もちろん、併用スピーカーの特性を補うこともできるし嗜好に合わせるという使い方にもつながるものだろう。
例のブラック・パネルのメカニカルなデザインと、機能的なレイアウトはかつてのＡＵ７７７をそのまま踏襲している。細かい特長を捨い上げてみると、接続カートリッジ間の入力回路が二つあるが、そのうち一つは、入力インピーダンスを30ｋΩ、50ｋΩ、1１００ｋΩの三段に切換えることができる。これは、カートリッジの出力インピーダンスのマッチングをとるという目的だが、適確なインピーダンス整合を計るという考え方から発展して、インピーダンス・マッチングによって変化する音帯の相違をトライするというマニア意欲を満たすサンスイらしい配慮であると見た。入力回路は、この他、チュ−ナー、ＡＵＸ、テープ・ライン、テープ・モニターなどと豊富であり、高級プリ・メイン・アンプとしての機能をよく備えている。また、入力感度３・５mVのマイク入力端子をもっていて、喫茶店などの使用には便利だが、これがピン・ジャック端子であることは考えもの。これは是非、マイク用として一般的なミニ・ジャックとすべきであろうし、できればフロント・バネルに出して欲しかった。出力回路としては、まず、プリ・アンプ出力が、かなりのハイ・レベルであることが、マルチ・アンプ・システム発展の時には大変便利である。そして、二系統のスピーカー出力端子が扱いやすいターミナルで出ている。フロント・パネルには、20dbのミューティング・スイッチ、ハイ、ロー・カット・フィルター、ボリューム・コントロールと同軸になったレバー式バランス・コントロールなどが整然と並んでいる。いかにもマニア好みのメカニカルな雰囲気ではあるが、素人には、馴れないと、あまり整然と並びすぎていて、かえって戸惑いを感じるようだ。特に、左右独立の六つのツマミからなるトリプル・トーン・コントロールとなったので、余計にぎやかな印象を与えるのであろう。
このアンプは、価格的には中級プリ・メイン・アンプであるが、サンスイの現役プリ・メイン・アンプを代表する製品で、その再生音の品位はかなり高い。定格30Ｗ＋30Ｗの出力は、現行商品の中では決して大パワーではないが、ジャズの再生に向く能率のよいスピーカーには十分な出力である。試聴に使ったアルテックのＡ７が堂々たる迫力を再現してくれたし、ブックシェルフ・タイプの数種のスピーカー・システムでも、特に不満は感じられなかった。従来のタイプの発展型だけに特に目新しさこそないが、それだけよく練られた、信頼度の高い製品だと思う。Translated (English Version)
Sansui AU-777D
Posted on November 20, 1969
Okihiko Kanno
Swing Journal December issue (published in November 1969)
From "SJ Selected New Product Listening Record"
The AU777D is a new model that improved the conventional AU777, and is a reliable and high-grade amplifier. AU777 is a product called the best-selling product, and it is an amplifier that solidifies the evaluation of Sansui's transistor amplifier, but with this D-type, it has become even better musically. Even if you listen to it, the rough roughness of the treble range, which I was a little worried about, has been greatly improved, and it has come to produce a smoother and plump sound. And the adoption of a triple tone control method that can control the band pass pattern in the middle range not only helps to adjust the room acoustic, but also confirms the great power of controlling the mid-tone range, which requires the most fulfillment for jazz playback. In general, when it is to make it a powerful sound, there is no tendency to enhance bass and treble, but this is not originally correct. Increasing the bass and high will make the middle and high frequencies thin, and it will never be a powerful sound, but a noisy sound. However, if you drop the low and high tones and close up the middle range, the wide range of the cutting angle will cry. The subtle control around here is the taste of sound making, but it's not that easy. This triple control allows you to adjust the middle range in 1 decibel step and +−5db, but this was effective because it was set to a very good characteristic curve. It is by no means an extreme increase or decrease, and the curve of the selection band is appropriate, and it can have a decent effect on any record. Of course, it can compensate for the characteristics of the combined speaker, and it will also lead to the use of matching it to your preferences.
The mechanical design and functional layout of the black panel follow the former AU777. If you throw away the fine features, there are two input circuits between the connection cartridges, one of which can switch the input impedance to three stages of 30kΩ, 50kΩ, and 1100kΩ. This is the purpose of matching the output impedance of the cartridge, but it developed from the idea of measuring the appropriate impedance alignment, and I saw it as a consideration like Sansui that satisfies the mania's desire to try the difference in the sound band that changes by impedance matching. In addition, the input circuit is abundant, such as tuner, AUX, tape line, tape monitor, etc., and has a good function as a high-grade pre-main amplifier. In addition, it has a microphone input terminal with an input sensitivity of 3.5 mV, which is convenient for use in coffee shops, etc., but it is conceivable that this is a pin-jack terminal. This should definitely be a common mini jack for microphones, and if possible, I wanted it to be put on the front bannel. As an output circuit, first of all, it is very convenient when developing a multi-amp system that the pre-amp output is quite high. And the two speaker output terminals come out in an easy-to-handle terminal. The front panel is neatly lined with 20db muting switches, high and low cut filters, volume control and coaxial lever balance control. It's a mechanical atmosphere that enthusiasts like, but for amateurs, if they don't get used to it, they're too orderly, and they seem to feel confused. In particular, it became a triple tone control consisting of six independent left and right nodles, so it will give an even more lively impression.
This amplifier is an intermediate pre-main amplifier in terms of price, but it is a product that represents Sansui's active pre-main amplifier, and the quality of its playback sound is quite high. The output of rated 30W + 30W is not a large power among current products, but it is enough output for efficient speakers suitable for jazz playback. Altec's A7, which I used for listening, reproduced the dignified power, and I didn't feel particularly dissatisfied with several speaker systems of the bookshelf type. There is no particular novelty only for the development type of the conventional type, but I think it is a highly reliable product that has been elaborated so well.
This Sansui AU-777D has been meticulously cleaned and restored, both inside and out, by our ex-Sansui Takumi (Craft Masters), who carried out a complete overhaul. While there are minor vintage wear marks on the side and back panels, while the front faceplate remains in excellent condition.
This amplifier has been very well looked after by its original Japanese owner. Since its return, it has been put through 2 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: 8/10 – Excellent overall, with common signs of age.
- Performance: 9/10 – 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 honor 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.
Please visit our YouTube channel, vintagejapanhifi_real, to enjoy audio demos of our special HiFi equipment, including vintage classics like the Micro Seiki DD-5, Sansui AU-20000, Hitachi IA-1000, and Yamaha CA-1000III. These recordings capture each piece’s unique sound profile and performance, helping you experience their quality before making a purchase.
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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.
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.
For optimal sound quality, we advise pairing this amplifier with a speakers that match its power efficiency. If you need guidance on amplifier matching, feel free to reach out for assistance.
Condition Note:
Given its age, this vintage hifi equipment remains an excellent choice, though it may show minor scratches, scuffs, or other signs of wear. Our condition ratings reflect over 20 years of expertise in vintage audio, so they’re based on both professional standards (same as audio shop) and personal experience.
Individual perceptions may vary, so we encourage careful review of the images provided. We’re also here to answer any questions you may have regarding the condition—please don’t hesitate to contact us for more details.