Sansui BA-90 (1968)
A compact all-silicon transistor stereo power amplifier released in August 1968
Overview
The Sansui BA-90 is a stereo power amplifier manufactured by SANSUI and released in August 1968. Designed for high-fidelity audio reproduction, it delivers 28W per channel into 8Ω and 32W into 4Ω at normal output, with significantly higher music power ratings of 70W and 90W respectively under IHF standards. The unit was originally priced at ¥36,300 and features a compact design measuring 187mm wide, 111mm high, and 363mm deep, weighing 7.5kg.
Specifications
| Year of Production | August 1968 |
| Effective power (8 Ω) | 28W/28W ± 1 dB |
| Effective power (4 Ω) | 32W/32W ± 1 dB |
| Music Power IHF (8 Ω) | 70W ± 1 dB |
| Music Power IHF (4 Ω) | 90W ± 1 dB |
| Harmonic distortion factor (at Normal Output) | 0.3% or Less |
| Harmonic distortion factor (at 1/2 output) | 0.1% |
| Harmonic distortion factor (at 1/10 output) | 0.1% |
| Intermodulation distortion factor (60 Hz : 7 kHz = 4 : 1) | 0.3% or less |
| Power Bandwidth IHF (8 Ω) | 15 Hz ~ 40 kHz |
| Frequency Characteristics (Normal Output) | 15 Hz to 100 kHz ± 1 dB |
| Input sensitivity (at rated output) | 1 V ± 3 dB |
| Input impedance | 100 kΩ or more |
| Load impedance | 4 Ω ~ 16 Ω |
| Damping factor (Low) | 10 (8 Ω) |
| Damping factor (High) | 50 (8 Ω) |
| Hum and noise (IHF) | 80 dB or more |
| Channel separation | 50 dB or more |
| Power supply voltage | AC100V/117V/220V/240V, 50Hz/60Hz |
| Power consumption | 160 VA |
| External dimensions | Width 187 × Height 111 × Depth 363 mm |
| Weight | 7.5 kg |
Design
The BA-90 uses a 3-stage direct-coupled output circuit with a PNP pre-driver and low-noise transistor to reduce distortion at low frequencies and small signal levels. It features a buffer amplifier to maintain constant input impedance regardless of the input adjuster setting and includes left/right independent volume controls and an input level adjuster for compatibility with various preamps. A damping factor selection switch allows optimization for different speakers, and an oral/null balance switch connects the speakers in series for precise balance adjustment. The amplifier includes a headphone jack, left/right phase selector switches, and a protective circuit using Sansui’s proprietary PSC system combined with a short-circuit fuse. Power transistors are mounted on an aluminum extrusion heat sink for effective thermal management.
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Related Models
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