Summary:
The Accuphase P-550 is a pretty powerful (270 WPC into 8 ohms, 420 WPC into 4 ohms, or 550 WPC into 2 ohms -- bridgeable to 840 W into 8 ohms or 1100 W into 4 ohms), fairly heavy (33 kg), and rather large (475 X 211 X 444 mm) solid-state stereo power amplifier. Build quality is superb inside and out, and the design and styling are, to my eye, drop-dead gorgeous. The heat sinks are fully enclosed within the chassis, resulting in nice clean lines without any sharp edges.The 15-mm-thick champagne-anodized front panel is beautifully finished and tastefully laid out. It is dominated by a pair of large illuminated power meters and a back-lit blue Accuphase logo. The meters, but not the logo :-(, can be turned off with a pushbutton provided in a small recess in the top of the unit, which also contains pushbuttons to switch the two sets of speaker outputs. The only front panel control is a rectangular power pushbutton below the meters. Although the amp is pretty heavy, there are no handles on the front, perhaps reflecting a design decision to compromise some functionality to achieve an elegant and non-industrial appearance.

The rear panel has two sets of speaker binding posts, which facilitates biwiring. The binding posts themselves are gold-plated, extremely thick (around 9-10 mm, so spade lugs have to be large), and cross-drilled to accept banana plugs. Two sets of inputs, also gold-plated, are provided: balanced and unbalanced. A rotary switch is used to select the four possible combinations of balanced/unbalanced and stereo/bridged mono operation. A nice touch is that there are large, solid handles on the back panel, so you can place the amp on its back without smashing the input and output connectors. The last items on the back panel are a 15-A circuit breaker and an IEC socket for the detachable power cable.

The amp runs quite cool. Even after several hours of driving inefficient speakers (83-dB sensitivity, 8-ohm load) at high volumes (-5 dB on the meters), the top panel is only warm to the touch. There are absolutely no turn-on or turn-off thumps. The amp is also completely silent during operation, and does not buzz or hum. Finally, it tends to sound good even when cold, although I usually let it warm up for 20 minutes or so just on general principles.

Well, about time I got to the sound! I first got hooked on the "Accuphase sound" when I upgraded from an Audiolab 8000S (used as preamp)/Acurus A-150 amp combo to an Accuphase E-406V integrated amplifier. I loved the clean sound of the E-406V, but it didn't have quite enough power (170 WPC) to drive my speakers, so I subsequently upgraded again to an Accuphase C-265 preamp and the P-550 power amp that I am reviewing here. All of the Accuphase components that I have owned seem to share the same sonic characteristics -- 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 overall presentation is crystal clear and highly refined, perhaps tending more toward "analytical" or "cool" than "lush" or "warm". I don't mean to suggest, however, that the P-550 is in any way anemic-sounding or lacking in bass power. The bass is very well controlled and quite extended. I guess what I am trying to express is more related to the midrange, which sounds somehow more "agile" [?] ("nimble" [?], "fluid" [?], "delicate" [?], "effortless" [?], "open" [?], "pristine" [?], "unsullied" [?] -- there must be a perfect word somewhere!) than with the other equipment I have heard. The treble has very similar characteristics, with excellent air, shimmer, and high-frequency extension, but (perhaps paradoxically) with a soft, organic, natural sound -- the antithesis of the hard, shrill, or piercing treble that many have ascribed to high-powered solid-state amps.

In summary, I think that the Accuphase P-550 is an excellent high-end power amplifier, and one that has been largely ignored by the audio press, which I find quite puzzling. It is, admittedly, rather expensive, but I feel that it is well worth its asking price. The P-550 is a state-of-the-art audio component that provides excellent sound, trouble-free operation, uncompromising build quality, intelligent design, and elegant styling.