Sansui AU 777D (1969)

An upgraded integrated amplifier from Sansui, released in June 1969. It builds on the AU-777 design with better sound quality and more control features.

Overview

The Sansui AU-777D is an integrated amplifier from Sansui Electric Co., Ltd., released in June 1969 as an upgrade to the milestone AU-777. It keeps the core circuit structure of the original and makes some partial changes aimed at sound quality. It is a pre-main amplifier with silicon transistors from input to output. You can use the preamp and main amplifier sections independently.

Specifications

Year of Production	1969
Rated Output (IHF)	70W ± 1 dB (8 Ω)
Effective Output	30W/30W ± 1 dB (8 Ω)
Total Harmonic Distortion	Not more than 0.5%
Intermodulation Distortion	Not more than 0.8% (60 Hz : 7 kHz = 4 : 1)
Power Band Width (IHF)	20 Hz ~ 50,000 Hz (Distortion Factor 0.5%)
Frequency Characteristic	20 Hz to 100,000 Hz, ± 1 dB
Channel Separation	20 dB or more (1000 Hz)
Hum and Noise (IHF)	100 dB or more (closed circuit)
Input Sensitivity / Impedance	1V / 300k Ω (Rated Output, 1 kHz)
Damping Factor	15 (8 Ω)
Load Impedance	4 Ω ~ 16 Ω
Center Channel Output Voltage	Flat Output: 10 V (1 kHz); High-Cut Output (fo = 159 Hz): 10 V (50 Hz)
Preamplifier Output Voltage	Maximum: 4 V; Rated: 1 V
Preamplifier THD	0.1% (Rated Output Voltage)
Preamplifier Frequency Response	20 Hz to 70,000 Hz, +0.5 -1.5 dB
Preamplifier Hum and Noise	Phono1,2: 80 dB+; MIC: 85 dB+; Tuner: 85 dB+ (open); AUX: 85 dB+ (open)
Input Sensitivity / Impedance (Preamplifier)	Phono1: 2 mV ±3dB / 50k Ω; Phono2: 2 mV ±3dB / 30k, 50k, 100k Ω; MIC: 3.5 mV ±3dB / 50k Ω; Tuner: 140 mV ±3dB / 100k Ω; AUX: 140 mV ±3dB / 100k Ω; Tape Mon (Pin): 140 mV ±3dB / 100k Ω; Tape Recorder (Din): 140 mV ±3dB / 100k Ω
Recorded Output	Tape Rec (Pin): 150 mV ±3 dB; Tape Recorder (Din): 30 mV ±3 dB
Bass Control	20 Hz ±15 dB (3 dB steps)
Midrange Control	1,500 Hz ±5 dB (1 dB steps)
Treble Control	20,000 Hz ±15 dB (3 dB steps)
Loudness	50 Hz +8 dB, 10,000 Hz +2.5 dB (at -30dB volume)
High Filter	20,000 Hz, -18dB (12dB/oct)
Low Filter	20 Hz, -26dB (12dB/oct)
Muting	-20dB
Configuration	31 transistors, 5 diodes
Power Supply Voltage	100 V, 50Hz/60Hz
Dimensions	435 mm (W) × 155 mm (H) × 334 mm (D)
Weight	12.5 kg
Walnut Wood Case	Sold separately (¥4,150)
Original Price	¥59,500

Design

The main amplifier uses a quasi-complementary Darlington circuit. NF amplifiers run through all stages - first input to final output - and the silicon transistors improve frequency response, distortion, and signal-to-noise ratio. The preamp and main amplifier sections can be used independently. Tone control is SANSUI's T.T.C. (Triple Tone Control), with adjustable midrange. There is also a stereo balance check circuit, and a pure electronic PSC circuit protects the power transistors from short circuits, backed by a fuse. The power transistors are mounted on a 3 mm aluminum extrusion back panel for heat dissipation. For 3D stereo setups, the center channel output offers both flat and 159 Hz high-cut options. The rest of the controls are low/high filters, loudness, tape monitor, a headphone jack, and a muting switch.

Context

The AU-777D is an upgraded version of the AU-777 (1967), which established Sansui's reputation for high-quality audio equipment. It was released in 1969 with refinements aimed at sound quality, and the core circuit design was left alone.

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