Sansui BA 2000
Stereo power amplifier with high-output transistors, dual toroidal transformers, and advanced OCL circuitry from the mid-1970s
Overview
The Sansui BA-2000 is a stereo power amplifier built during the peak of Japanese high-fidelity engineering. It delivers 110 watts per channel into 8 ohms with exceptionally low distortion and wide frequency response. Designed for precision and reliability, it features a fully DC-coupled signal path, independent power supplies for critical stages, and comprehensive protection circuits for both output transistors and speakers.
Specifications
| Power output | 110W + 110W into 8Ω |
| Effective output (20 Hz – 20 kHz) | 110W + 110W (8 Ω, THD 0.03%) |
| Total harmonic distortion | 0.03% or less (4 Ω, 1W); 0.05% or less (4 Ω, rated) |
| Frequency response | 5 Hz to 100 kHz ±0 –1dB (at 1W output) |
| Signal-to-noise ratio | 115 dB or more (IHF, A-network, short circuit) |
| Channel separation | 75 dB or more (1 kHz) |
| Input sensitivity | 1V |
| Input impedance | 50k Ω |
| Power consumption | 245W (rated), 910W maximum |
| Dimensions | Width 460 x Height 176 x Depth 415 mm |
| Weight | 18.3kg |
| Original price | ¥120,000 (around 1976) |
Design
The BA-2000 uses a refined fully complementary OCL circuit with all stages directly coupled. The differential amplifier employs a newly developed dual transistor with matched operating and thermal characteristics. The pre-drive stage is a two-stage class A amplifier with active load, while the drive stage uses a three-stage Darlington connection in parallel push-pull configuration, with two high-output transistors per channel. The power supply uses dual-winding toroidal transformers, high-capacity rectifiers, and large electrolytic capacitors, with ±2 independent power supplies for pre-drive and drive stages—stabilized by a constant current circuit in the pre-drive. Output transistors are protected by safe operating area (ASO) current limiting and temperature detection, while the speaker is guarded by a DC detection relay. A large, logarithmic-compression power meter with three-range switching (x1, x1/10, x1/100) displays output from 0.001W to 110W. The driver, output, and power supply sections are physically isolated in a block configuration, and heat dissipation is managed by a chimney-type heatsink with four convective radiators (1,200cc envelope volume).
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Related Models
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