Accuphase B-6 (1978)
Power bridge network made only for specific Accuphase amplifiers, with a DC-coupled NF loop and no capacitors at the input or output.
Overview
The Accuphase B-6 is a power bridge network from Accuphase Laboratory, Inc. (originally Kensonic Laboratory, Inc.). It came out in 1978 at an original price of ¥25,000. It was built only for the Accuphase M-60, P-300S, and P-300 power amplifiers and won't work with any other Accuphase product. The buffer and phase inversion circuits use an operational amplifier IC with good high-frequency performance and low noise, which keeps sound coloration to a minimum.
Specifications
| Gain | 0dB |
| Maximum Output | 5.0V |
| Harmonic Distortion | 0.01% (20Hz–20kHz, 5.0V output) |
| Frequency Response | 20Hz–20kHz +0 -0.2dB; DC–600kHz +0 -1.0dB |
| Input Impedance | 100kΩ |
| Output Impedance | 100Ω |
| S/N Ratio | 110dB (IHF-A, 20Hz–20kHz, 2.0V output) |
| Power Supply | AC100V, 50Hz/60Hz |
| Power Consumption | 4W |
| Dimensions | 184mm (W) × 77mm (H) × 197mm (D) |
| Weight | 2.0kg |
Design
The buffer and phase inversion stages of the B-6 use an operational amplifier IC with excellent high-frequency characteristics and signal-to-noise performance. The negative feedback (NF) loop is DC-coupled. There are no capacitors at the input or output, so none of them can color the sound. No phase correction is needed across a wide bandwidth, which helps keep the signal intact and holds off sound quality degradation.
Context
The B-6 was designed only for the Accuphase M-60, P-300S, and P-300 amplifiers. It is not compatible with other models in the Accuphase lineup, which points to a tightly coupled system approach in the company's early product strategy.
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