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). It has 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 very low distortion and a frequency response out to 50 kHz. It has a fully direct-coupled signal path and a triple tone control system with selectable midrange and treble frequencies. Input switching is extensive, with multiple phono options. Protection systems cover both the speakers and the output transistors.
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. The first stage of the power amplifier is a differential-amplifier circuit, and the output stages are parallel push-pull using matched transistors. The equalizer amplifier uses a two-amplifier configuration with a differential input and a dual-transistor setup. It divides the audio band into high and low sections, corrected via CR and NF feedback, to get accurate RIAA equalization up to ultra-high frequencies. A dynamic margin of 300 mV is maintained using dual ± high-voltage power supplies. The triple tone control has selectable midrange and treble frequencies, and a tone defeat switch gives flat response. Volume level offsets are selectable at 0 dB, -10 dB, or -20 dB. Input sensitivity and impedance switch across three levels to match cartridge characteristics. Other controls include a two-circuit tape play switch, tape copy switch, low/high filters, tuner priority selector, muting switch, and side input/output terminals. The protection circuit monitors output stage temperature and DC offset. It uses electronic detection and relays to safeguard the speakers and transistors, and it includes an ASO current limiter. The chassis puts the preamplifier and tone controls at the front and the power supply at the rear, with fully isolated block stages. A toroidal power transformer minimizes magnetic leakage.
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