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 produced by Sansui Electric Co., Ltd., released in 1975. It delivers 35W + 35W into 8Ω across 40Hz to 20kHz, with peak power of 40W + 40W under single-channel conditions at 1kHz. Designed with a ±2 power supply system, it eliminates coupling capacitors in signal paths for direct coupling throughout all stages. The unit includes phono (MM), microphone, tuner, and auxiliary inputs, with tape monitoring and dual 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 use a direct-coupled OCL (Output Capacitor-Less) circuit with a ±2 power supply system, eliminating coupling capacitors for improved signal purity. The differential amplifier core uses matched dual transistors for stable operation despite DC fluctuations. The complementary output stage uses same-polarity power transistors (NPN-NPN and PNP-PNP) in a pure output configuration. The phono equalizer employs a PNP-NPN two-stage direct-coupled circuit with low-noise transistors and precision components. The tone control section uses a two-stage direct-coupled amplifier with a CR-type circuit and high-accuracy elements. Input switching is handled by an all-push-button selector that minimizes click noise via the dual power supply. A protection circuit combines electronic monitoring and relay action. The unit includes a microphone mixing circuit with level control, allowing mixed output via the recording terminal, and provides two speaker outputs. Volume is adjusted via a Klix/Klukš top-type knob with 10-stage precision.
Features
The AU-3300 includes loudness control, high-cut and low-cut filters, -20dB audio muting, stereo/mono switching, and
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