Sansui AU 777D (1969)

An upgraded integrated amplifier from Sansui, released in June 1969, building on the acclaimed AU-777 design with enhanced sound quality and expanded control features.

Overview

The Sansui AU-777D is an integrated amplifier produced by Sansui Electric Co., Ltd., released in June 1969 as an upgraded version of the milestone AU-777. It retains the core circuit structure of its predecessor while incorporating partial improvements focused on sound quality. The unit features a pre-main amplifier configuration with full silicon transistor circuitry from input to output, and allows for independent use of the preamp and main amplifier sections.

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 AU-777D uses a quasi-complementary Darlington circuit in the main amplifier section and employs NF amplifiers throughout all stages—from first input to final output—using silicon transistors to improve frequency response, distortion, and signal-to-noise ratio. The preamp and main amplifier sections can be used independently. It features SANSUI’s T.T.C. (Triple Tone Control) with adjustable midrange, a stereo balance check circuit, and a pure electronic PSC circuit to protect power transistors from short circuits, backed by a fuse. The power transistors are mounted on a 3 mm aluminum extrusion back panel for improved heat dissipation. The unit includes a center channel output with both flat and 159 Hz high-cut options for 3D stereo setups, along with low/high filters, loudness, tape monitor, headphone jack, and 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. The AU-777D was released in 1969 with refinements focused on sound quality without altering the core circuit design.

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