Accuphase P-11 (1989)
Stereo power amplifier released in July 1989, with dual monaural construction and a fully balanced topology.
Overview
The Accuphase P-11 is a stereo power amplifier made in Japan and released in July 1989. It uses dual monaural construction, fully balanced circuitry and a push-pull parallel output stage. The signal path is direct-connected with a DC servo system. Inputs are unbalanced phono and full-scale balanced. It runs in stereo, or you can switch it to monaural by bridge connection, and then it delivers up to 340W into 8 Ω. Two speaker outputs allow A, B or A+B operation, and independent high-current relays make bi-wiring possible. The front panel has a champagne gold scratch hairline finish, a thick glass display and thick metal end blocks.
Specifications
| Power Output (stereo) | 150W/ch (4 Ω), 120W/ch (8 Ω), 60W/ch (16 Ω) |
| Power Output (monaural, bridge) | 340W (8 Ω), 240W (16 Ω) |
| THD (stereo) | 0.03% (4 Ω), 0.01% (8–16 Ω) |
| THD (monaural) | 0.02% (8–16 Ω) |
| IM Distortion | 0.003% |
| Frequency Response | 20 Hz – 20 kHz ±0.2 dB; 0.5 Hz – 160 kHz –3.0 dB |
| Gain | 28.0 dB (stereo and monaural) |
| Damping Factor | 200 (stereo), 100 (monaural) |
| Input Sensitivity (8 Ω) | 1.2 V (stereo), 2.08 V (monaural) |
| Input Impedance | 40k Ω (balanced), 20k Ω (unbalanced) |
| S/N Ratio | 120 dB (input short), 93 dB (1W output) |
| Headphone Impedance | 4 Ω – 100 Ω |
| Power Supply | AC100V/117V/220V/240V, 50Hz/60Hz |
| Power Consumption | 45W (no input), 300W (regulatory), 480W (8 Ω rated) |
| Dimensions | 445 mm (W) × 131 mm (H) × 388 mm (D) |
| Weight | 18.1 kg |
| Semiconductors | 41 Transistors, 14 FETs, 4 ICs, 60 Diodes |
Design
The P-11 is dual monaural, fully balanced and push-pull parallel. The voltage amplification stage is a differential amplifier, followed by a FET cascode buffer stage that keeps the preamp from interfering. The driver stage uses an original power MOS FET unique to Accuphase. The output stage has three parallel push-pull large-output transistors with 130W collector loss, and each channel uses four pairs of Sanken SAP15N/P transistors. One large toroidal transformer feeds separate windings to the front and output stages, and the front stage gets its own left/right rectifiers and filters. The input is direct-coupled with a DC servo system. Level control is a 1 dB step double attenuator. There is also an overload indicator and remote control capability.
Context
The Accuphase P-11 came out in July 1989 in Japan, during the "Golden Age" of high-end Japanese audio equipment. It is listed among Accuphase's "Classic Models Reference."
Market
The Accuphase P-11 was originally priced at ¥230,000. It has been listed for €2,450.00 on Taste For Audio, previously at €2,870.00, and was also listed for $1,800 five years ago. Units in good condition show natural aging such as scratches and yellowing, but have been confirmed to operate flawlessly.
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