Accuphase P-370 (2001)
It weighs 24.4kg. No frills, just measured power.
Overview
The Accuphase P-370 is a stereo power amplifier released in March 2001. It was priced at ¥360,000 at launch and was never meant for casual listeners. It is built for people who want control, precision, and the ability to drive difficult speaker loads. It delivers 150W per channel into 4Ω and 75W into 8Ω. Its real strength is stability. It can handle a 2Ω stereo load (and 1Ω with music signals), thanks to a heavy output stage and a massive power supply.
The design centers on a current feedback amplifier circuit, which Accuphase uses to minimize phase error and keep bandwidth wide. The output stage uses high-power transistors rated for 150W collector loss and 15A collector current, arranged in triple parallel push-pull and mounted on a large heatsink. The heatsink is needed because the amplifier draws a 475W maximum under test conditions. The power supply uses a super-ring type toroidal transformer of approximately 700 VA, feeding two 47,000 μF aluminum electrolytic capacitors for instant current delivery.
Balanced operation is supported through dedicated XLR inputs, and the amplifier can be bridged for monaural use, doubling its output into 4Ω or 8Ω loads. The dual speaker terminals allow bi-wiring, though the manual notes they are normally used by switching between A and B systems. Construction is all metal with a clean internal layout.
The P-370 has a damping factor of 200, which keeps tight control over the speaker cones. Its signal-to-noise ratio is 120 dB (A-weighted), so the background is virtually silent. Total harmonic distortion is rated at 0.02% across 4Ω to 16Ω loads, rising only to 0.05% at 2Ω. Intermodulation distortion is 0.003%. Frequency response is flat from 20Hz to 20kHz at full power and extends to 160kHz at 1W. That is far beyond audibility, but it points to transient speed and phase coherence.
Specifications
| Manufacturer | Accuphase |
| Model | P-370 |
| Type | Stereo power amplifier |
| Production year | March 2001 |
| Original price | ¥ 360,000 |
| Rated continuous average output (stereo) | 400W/ch (1 Ω, music signal only), 300W/ch (2 Ω), 150W/ch (4 Ω), 75W/ch (8 Ω) |
| Rated continuous average output (monaural/bridge) | 800W (2 Ω, music signal only), 600W (4 Ω), 300W (8 Ω) |
| Total harmonic distortion factor (stereo) | 0.05% (2 Ω Load), 0.02% (4 Ω ~ 16 Ω Load) |
| Total harmonic distortion factor (monaural) | 0.02% (4 Ω ~ 16 Ω Load) |
| IM distortion factor | 0.003% |
| Frequency characteristic | 20 Hz ~ 20 kHz + 0 -0.2 dB (at rated continuous average output), 0.5 Hz ~ 160 kHz + 0 -3.0 dB (at 1W Output) |
| Gain | 28.0 dB (both stereo and monaural) |
| Load impedance (stereo) | 2 Ω ~ 16 Ω |
| Load impedance (monaural/bridge) | 4 Ω ~ 16 Ω |
| Damping factor | 200 |
| Input sensitivity (stereo, 8 Ω) | 0.98 V (at rated output), 0.11 V (at 1W output) |
| Input sensitivity (monaural/bridge, 8 Ω) | 1.95 V (at rated output), 0.11 V (at 1W output) |
| Input impedance | Unbalanced input: 20k Ω, Balance Input: 40k Ω |
| S/N | 120 dB (at rated continuous average output) |
| Output meter | Logarithmic Compression Type with Display / Off Function -50dB to + 3 dB |
| Power | 100 VAC, 50Hz/60Hz |
| Power consumption | 44W (non-input), 475W (Electrical Appliance and Material Control Law), 335W (at 8 Ω load rated output) |
| Dimensions | Width 475 x Height 180 x Depth 417 mm |
| Weight | 24.4kg |
Key Features
Current Feedback Amplifier Circuit
The P-370 uses a current feedback topology, which favors high slew rate and wide bandwidth over traditional voltage feedback. That gives faster transient response and better phase linearity across the audible spectrum. Many amplifiers roll off sharply at the extremes. The P-370 keeps stability and low distortion even at the edges of its frequency range.
Triple Parallel Push-Pull Output Stage
Each channel uses three high-power transistors in parallel per side of the push-pull configuration. Each transistor is rated for 150W collector loss and 15A collector current. Paralleling them reduces stress on the individual devices, improves thermal stability, and lets the amplifier sustain high current into low-impedance loads. The output stage sits on a large heatsink and is built for long-term high-power operation without thermal runaway.
Super-Ring Type Toroidal Transformer (700 VA)
The power supply is built around a super-ring type toroidal transformer of approximately 700 VA. This design minimizes magnetic leakage and mechanical vibration while giving a rigid voltage foundation. Paired with two 47,000 μF aluminum electrolytic capacitors, it provides large current reserves, so the amplifier does not starve under dynamic demand when driving complex speaker loads.
Balanced Input and Bridge-Monaural Operation
The balanced XLR inputs allow noise-resistant connection, especially over longer cable runs. The P-370 can also be bridged for monaural operation, which doubles its voltage swing and output power. In this mode it delivers 600W into 4Ω or 300W into 8Ω, which suits it for use as a dedicated subwoofer or main amplifier in bi-amped setups.
Analog Power Meter with Off Switch
A large analog power meter shows output levels in real time, using logarithmic compression to cover a range from -50dB to +3dB. A front-panel switch turns off both the meter movement and its backlight, which helps in dark listening rooms.
Dual Speaker Terminals for Bi-Wiring
The rear panel has two sets of speaker terminals (A and B). They can switch between speaker pairs, or when both are engaged, enable bi-wiring. That allows separate cables for the woofer and the midrange/tweeter sections of bi-wireable speakers, though the benefit is debated. The terminals accept thick gauge cables, which fits the high-current design.
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Service Manuals, Schematics & Catalogs
- Catalog (1992) — archive.org
- Catalog (1990) — archive.org