Sansui AU-3300 (1975)

Japanese solid-state integrated amplifier with direct-coupled OCL design and comprehensive feature set

Overview

The Sansui AU-3300 is an integrated amplifier from Sansui Electric Co., Ltd., released in 1975. It puts out 35W + 35W into 8Ω across 40Hz to 20kHz. Peak power is 40W + 40W with a single channel driven at 1kHz. The ±2 power supply system lets the signal path run without coupling capacitors, so every stage is direct coupled. Inputs are phono (MM), microphone, tuner and auxiliary. There is tape monitoring and two speaker outputs.

Specifications

Year of Production	1975
Effective power (both channels, 8 Ω, 40 Hz to 20 kHz)	35W + 35W
Effective power (both channels, 8 Ω, 1 kHz)	38W + 38W
Effective power (single channel, 8 Ω, 1 kHz)	40W + 40W
Music power (4 Ω, 1 kHz)	140W
Total harmonic distortion factor	Not more than 0.15%
Intermodulation Distortion Factor (70 Hz : 7 kHz = 4 : 1, SMPTE)	0.2% or Less (Rated Output)
Power Bandwidth (IHF, 8 Ω)	10 Hz ~ 40 kHz
Frequency Response (at 1W)	10 Hz ~ 40 kHz +0.5 -1.5 dB
RIAA deviation (30 Hz to 15 kHz)	± 0.5 dB
Damping factor (8 Ω)	50
Input Sensitivity / Impedance Phono	2.5mV/50k Ω
Input Sensitivity / Impedance Mic	2.5mV/10k Ω
Input Sensitivity / Impedance Tuner, Aux, Tape Monitor	130mV/50k Ω
Phono maximum allowable input	230 mV (1 kHz, THD 0.2% or less)
Output Voltage (1 kHz) Tape Rec (Pin)	100mV
Channel Separation (1 kHz) Phono	60 dB or more
Channel Separation (1 kHz) Tuner, Aux, Tape rec	65 dB or higher
Hum and noise Phono	75 dB or more
Hum and noise Mic	65 dB or more
Hum and noise Aux, Tuner, Tape Monitor	90 dB or higher
Tone control Bass	± 12 dB (50 Hz)
Tone control Treble	± 12 dB (15 kHz)
Loudness (at Volume -30dB)	+10 dB at 50 Hz, +8 dB at 10 kHz
High filter	-3dB (7 kHz), 6dB/oct.
Low filter	-3dB (100 Hz), 6dB/oct.
Muting	-20dB
Power consumption (Rating)	76W
Power consumption (maximum)	210W
External dimensions	Width 400 x Height 120 x Depth 240 mm
Weight	6.3kg
Original price	¥39,800

Design

All signal stages are direct-coupled OCL (Output Capacitor-Less), run from a ±2 power supply system. No coupling capacitors anywhere. The differential amplifier core uses matched dual transistors, which keeps it stable when the DC level drifts. The complementary output stage uses same-polarity power transistors (NPN-NPN and PNP-PNP) in a pure output configuration. The phono equalizer is a PNP-NPN two-stage direct-coupled circuit with low-noise transistors and precision components. The tone control section is a two-stage direct-coupled amplifier with a CR-type circuit and high-accuracy elements. Input switching is all push-button, and the dual power supply keeps click noise down. The protection circuit combines electronic monitoring with a relay. A microphone mixing circuit with level control sends the mixed output to the recording terminal. There are two speaker outputs. Volume is set with a Klix/Klukš top-type knob with 10-stage precision.

Features

The AU-3300 has loudness control, high-cut and low-cut filters, -20dB audio muting, stereo/mono switching, and

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