Accuphase P-550 (1994)

Name: Accuphase P-550
Brand: Accuphase

A high-power stereo amplifier released in April 1994 with current feedback topology and extensive use of gold-plated, high-purity signal path components.

Overview

The Accuphase P-550 is a stereo power amplifier manufactured by Accuphase Laboratory, Inc., released in April 1994. It delivers 550W per channel into 2 Ω, 420W into 4 Ω, and 270W into 8 Ω, with monaural (bridged) output of 1100W into 4 Ω and 840W into 8 Ω. Priced at ¥580,000 at launch, it features a current feedback circuit design, balanced and unbalanced inputs, and a robust build with a 15-mm-thick front panel and gold-plated internal signal paths.

Specifications

Production Year	April 1994
Output Power (stereo)	550W/ch (2 Ω), 420W/ch (4 Ω), 270W/ch (8 Ω)
Output Power (monaural, bridged)	1100W (4 Ω), 840W (8 Ω)
Total Harmonic Distortion	0.05% (2 Ω), 0.02% (4 Ω–16 Ω)
IM Distortion	0.003%
Frequency Response	20 Hz – 20 kHz (+0, -0.2 dB) at rated output; 0.5 Hz – 160 kHz (+0, -3.0 dB) at 1W
Gain	28.0 dB (stereo and monaural)
Damping Factor	500 (stereo), 250 (monaural)
Input Sensitivity (8 Ω)	1.85 V (stereo, full output), 3.26 V (monaural, full output)
Input Impedance	20k Ω (unbalanced), 40k Ω (balanced)
S/N Ratio	123 dB (A-weighted, input shorted)
Power Supply	100 VAC, 50/60 Hz
Power Consumption	200W (idle), 980W (max, per Electrical Appliance Law), 920W (8 Ω rated output)
Dimensions	475 mm (W) × 211 mm (H) × 444 mm (D)
Weight	33.0 kg

Design

The P-550 uses a current feedback amplifier circuit with the output signal fed back as current. The output stage employs ten parallel audio power transistors with a high-output multi-emitter structure (130W collector loss, 15A collector current). The drive stage uses power MOS FETs with negative thermal characteristics. A 1200 VA toroidal transformer and dual 47,000 μF/100WV electrolytic capacitors supply power. High-purity copper with gold plating is used in signal paths, including the PCB copper foil, grounding board, bus bars, input terminals, and speaker terminals. Input terminals are about ten times thicker than standard. The amplifier features balanced inputs via direct signal injection to non-inverting and inverting inputs, two sets of gold-plated speaker binding posts (cross-drilled for banana plugs) for bi-wiring, and both balanced and unbalanced gold-plated inputs. A rotary switch selects input type and stereo/bridged mono mode. The front panel is 15-mm-thick champagne-anodized aluminum with large illuminated analog power meters, a back-lit blue Accuphase logo, and a recessed top panel with buttons to turn off meters and switch speaker outputs. Heat sinks are fully enclosed, large rear handles are provided, and the unit operates silently without turn-on/off thumps, running only slightly warm after extended use.

Reception

Reviewer David Spear described the P-550 as having "extremely pure and transparent sound, precise imaging, a wide and deep soundstage, excellent micro- and macrodynamic contrast, and absolutely no hardness, harshness, congestion, or grundge." The presentation is "crystal clear and highly refined," leaning "analytical" or "cool" rather than "lush" or "warm." Bass is "very well controlled and quite extended," midrange is "agile, nimble, fluid, delicate, effortless, open, pristine, unsullied," and treble offers "excellent air, shimmer, and extension" with a "soft, organic, natural sound," avoiding the harshness often associated with high-powered solid-state amplifiers. The amplifier performs well even when cold, though warming up for 20 minutes is typical. It is considered a state-of-the-art component with excellent sound, trouble-free operation, uncompromising build quality, intelligent design, and elegant styling, "well worth its asking price."

Market

Listings for the Accuphase P-550 include a unit priced at €4,600 (Audio-markt, Jan 26, 2025), PLN 29,000 (OLX Poland, Mar 17, 2024), and brochures available for €6 (Kleinanzeigen, Jan 27, 2026 and Jan 7, 2023). An original English information folder exists.

eBay Listings

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