Sansui AU-11000A
A high-power stereo pre-main amplifier from Sansui, released in 1975 (per audio-database.com) or 1977–1979 (per Audiovintageshop and HiFiEngine) with precision engineering and advanced protection circuitry.
Overview
The Sansui AU-11000A is a stereo pre-main amplifier produced by SANSUI. It delivers 110 watts per channel into 4 or 8 ohms with exceptionally low distortion and a wide frequency response extending to 50 kHz. Designed for audiophiles seeking high fidelity, it features a fully direct-coupled signal path, a unique triple tone control system with selectable midrange and treble frequencies, and comprehensive input switching including multiple phono options. The unit integrates advanced protection systems for both speakers and output transistors, combining performance with reliability.
Specifications
| Effective output (both channel operation) | 110W + 110W (4 Ω, 8 Ω, 20 Hz to 20 kHz) |
| Total harmonic distortion factor (rated output) | Not more than 0.08% |
| Intermodulation Distortion Factor (70 Hz : 7 kHz = 4 : 1, SMPTE) | Not more than 0.08% |
| Frequency Response (at 1W) | 10 Hz to 50 kHz +0 -1dB |
| Damping factor | 80 (8 Ω) |
| RIAA deviation (30 Hz to 15 kHz) | ± 0.3 dB |
| Load impedance | 4 Ω, 8 Ω |
| Channel Separation (1 kHz) | Phono1 and 2 : 55 dB or more; Tuner, Aux1, 2, Tape Monitor : 60 dB or higher |
| Hum and noise | Phono1, 2 : 65 dB or more; Tuner, Aux1, 2, Tape Monitor : 80 dB or higher |
| Input Sensitivity / Impedance (1 kHz) | Phono1 : 2 mV, 4 mV, 8mV/30k Ω, 50k Ω, 100k Ω; Phono2 : 2mV/50k Ω; Tuner, Aux1, 2, Tape Monitor1 : 135mV/50k Ω; Tape Monitor2(Pin/Din):130mV |
| Maximum allowable input (1 kHz, THD 0.1% or less) | Phono1 : 1000 mV (Input Sensitivity Switching 8 mV); Phono2:300mV; Aux, Tuner : 3 v |
| Clipping point (aux/tuner/tape) | 20V (Hi-Fi Choice 1977) |
| Input impedance on mic at minimax volume | 49k 200pF (Hi-Fi Choice 1977) |
| Output level | Tape rec1(Pin):130mV; Tape rec2(Pin/Din):130mV/30mV |
| Tone control | Bass : ± 10 dB (30 Hz); Midrange : ± 5 dB (1.5 kHz); Treble : ± 10 dB (20 kHz) |
| Tone selector | Bass : 150 Hz, 300 Hz, 600 Hz; Treble : 2 kHz, 4 kHz, 8 kHz |
| Low filter | -3dB at 20 Hz, 12dB/oct.; -3dB at 60 Hz, 12dB/oct. |
| High filter | -3dB (7 kHz), 6dB/oct.; -3dB at 12 kHz, 12dB/oct. |
| Rated power consumption | 240W |
| External dimensions | Width 460 x Height 160 x Depth 375 mm |
| Weight | 19.3kg |
Design
All stages are directly connected using a pure complementary OCL system, with a differential-amplifier circuit at the first stage of the power amplifier and parallel push-pull output stages using matched transistors. The equalizer amplifier uses a two-amplifier configuration with a differential input and dual-transistor setup, dividing the audio band into high and low sections corrected via CR and NF feedback to achieve accurate RIAA equalization up to ultra-high frequencies. A dynamic margin of 300 mV is maintained using dual ± high-voltage power supplies. The design includes a unique triple tone control with selectable midrange and treble frequencies, a tone defeat switch for flat response, and selectable volume level offsets of 0 dB, -10 dB, or -20 dB. Input sensitivity and impedance can be switched across three levels to match cartridge characteristics. The amplifier features a two-circuit tape play switch, tape copy switch, low/high filters, tuner priority selector, muting switch, and side input/output terminals. A built-in protection circuit monitors output stage temperature and DC offset, using electronic detection and relays to safeguard speakers and transistors, including an ASO current limiter. The chassis layout separates preamplifier and tone controls to the front and power supply to the rear, with fully isolated block stages and A toroidal power transformer minimizes magnetic leakage.
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