Accuphase PRO-20 (1994)
Stereo power amplifier released in January 1994, designed for studio use.
Overview
The Accuphase PRO-20 is a stereo power amplifier manufactured by Accuphase Laboratory, Inc., released in January 1994. It was developed specifically as a studio-dedicated amplifier, emphasizing precision and power delivery. The unit can operate in monophonic bridge mode via a rear-panel switch, functioning as a balanced monaural power amplifier.
Specifications
| Output Power (Stereo) | 300W + 300W (2Ω), 200W + 200W (4Ω), 100W + 100W (8Ω) |
| Output Power (Monophonic, Bridge) | 600W (4Ω), 400W (8Ω) |
| Total Harmonic Distortion | 0.05% (2Ω), 0.02% (4Ω–16Ω) stereo; 0.02% (4Ω–16Ω) mono |
| Frequency Response | 20Hz–20kHz ±0.2dB (full power); 0.5Hz–160kHz ±3dB (1W, max level) |
| Dimensions | 475mm (W) × 238.5mm (H) × 548mm (D) |
| Weight | 46.8 kg |
| Power Supply | AC110V/117V/220V/240V, 50Hz/60Hz |
| Power Consumption | 310W (no input), 550W (max), 375W (8Ω rated output) |
| Input Impedance | Balanced: 40kΩ, Unbalanced: 20kΩ |
| Damping Factor | 160 (stereo), 140 (mono bridge) |
| S/N Ratio | 110 dB (A-weighted, input shorted) |
| Gain | 28.0 dB (stereo and mono) |
Design
The PRO-20 uses a 10 parallel push-pull configuration with 20 MOS-FETs per channel, with allowable loss power of 120W per channel. The input stage features Accuphase’s balanced differential pure complementary push-pull circuit, modularized with a hybrid IC. FET buffers provide high input and low output impedance on both input phases. All signal path PCBs and oxygen-free copper bus boards are gold-plated. Power is delivered via a 1,000 VA toroidal transformer and dual 56,000 μF filter capacitors. Cooling is passive, using a large aluminum die-cast heat sink. Input terminals include RCA and XLR connectors.
Context
The PRO-20 was developed as a studio-dedicated amplifier, reflecting Accuphase's focus on high-precision audio equipment for professional environments.
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