Accuphase A-50V (1998)
A pure class A stereo power amplifier released in December 1998 with high-power output and precision current feedback design.
Overview
The Accuphase A-50V is a pure class A stereo power amplifier designed using M-2000 design technology. Released in December 1998, it delivers up to 400 watts per channel into 1 ohm in stereo mode and can be bridge-connected for monaural operation, reportedly producing up to 800 watts into 2 ohms. It features a current feedback amplifier circuit, balanced input terminals, and a digital power meter for real-time output monitoring.
Specifications
| Rated continuous average power (20 Hz - 20 kHz) Stereo | 400W/ch (1 ohm), 200W/ch (2 Ω), 100W/ch (4 Ω), 50W/ch (8 Ω) |
| Rated continuous average power (20 Hz - 20 kHz) Monaural (bridge connection) | reportedly 800W (2 Ω), 400W (4 Ω), 200W (8 Ω) |
| Total Harmonic Distortion Factor Stereo | reportedly 0.05% (2 Ω), 0.03% (4 Ω - 16 Ω) |
| Total Harmonic Distortion Factor Monaural | 0.03% (4 Ω - 16 Ω) |
| IM Distortion Factor | 0.003% |
| Frequency Response | 20 Hz to 20 kHz + 0 -0.2 dB at rated continuous average output |
| Frequency Response | reportedly 0.5 Hz ~ 160 kHz + 0 -3.0 dB at 1W Output |
| Gain | 28.0 dB (both stereo and monaural specifications) |
| Load Impedance Stereo | 1 Ω ~ 16 Ω |
| Load Impedance Monaural specification | 2 Ω ~ 16 Ω |
| Damping factor | 100 (both stereo and monaural specifications) |
| Input sensitivity (8 Ω load) Stereo | reportedly 0.80 V at rated continuous average power, 0.11 V at 1W output |
| Input sensitivity (8 Ω load) Monaural | reportedly 1.59 V at rated continuous average power, 0.11 V at 1W output |
| Input Impedance Balance | 40k Ω |
| Input Impedance Unbalanced | 20k Ω |
| S/N (A correction) | 110 dB at input short circuit, rated continuous average output |
| Digital Output Meter Type | True value display type of power |
| View Range | 0.1W ~ 400.0W (Stereo), 1W ~ 2000W (monaural specification) |
| Hold Time | 1 second / ∞ |
| Switching Type | With Display / Off function |
| Power Supply | 100 VAC, 50Hz/60Hz |
| Power Consumption No input | reportedly 310W |
| Power Consumption Electrical Appliance and Material Control Law | 550W |
| Power Consumption 8 Ω rated output | reportedly 380W |
| External Dimensions | 475 mm wide x 239 mm high x 545 mm deep |
| Weight | 45.1kg |
Design
The A-50V uses a current feedback amplifier circuit that feeds back the output signal as current, maintaining stable output voltage under varying loads. The output stage employs 10 pairs of power MOS FETs per channel in parallel push-pull configuration, each pair handling only 5W of power despite a 120W per FET rating. Power MOS FETs are also used in the driver stage with cascode connection to extend frequency response and reduce negative feedback. High-purity copper with gold plating is used on signal-carrying components, including the PCB, earth plate, capacitors, and terminals. The speaker terminals are machined from solid brass, gold-plated, and insulated with mold caps. A large, reportedly 1 kVA toroidal transformer and two 82,000 μF aluminum electrolytic capacitors supply power. The amplifier can be bridge-connected for monaural use and includes balanced inputs.
Market
A forum post from August 8, 2023, noted two units for sale, with the listed price applying per unit.
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Service Manuals, Schematics & Catalogs
- Catalog (1991) — archive.org
- Catalog (1992) — archive.org
- Catalog (1990) — archive.org