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Can cool-running amplifiers sound good?

Class D amplifiers run cool to the touch, but they haven't always sounded great. Now they're gaining favor with audiophiles.

The Pioneer Elite SC-57 receiver Pioneer Electronics

I admit it, most of my favorite amplifiers produce enough heat to warm up a room and consume a lot of AC power. "Green," they are not. Class D amplifier designs (the "D" does not stand for digital) are vastly more efficient, and run cool to the touch.

For example, my Bel Canto REF500S power amp ($2,495) puts out 250 watts per channel, and it's a bona fide audiophile quality design. Bel Canto doesn't specifically refer to the REF500S as a Class D amp, but its low-heat, ultraefficient, heavily regulated switch-mode power supply and switching output stage use a minimum of AC power. Class D home theater receivers' sound quality isn't in the same league. Well, that's what I thought before I read Michael Fremer's glowing review of Pioneer's Elite SC-57 receiver ($2,100) in Home Theater magazine.

He thinks the SC-57 can produce a "noticeably warm, rich, coherent sound," which would be a major improvement over the Class D receivers I've heard. Fremer went on, "An experienced listener might note an exceptionally well-damped, tight bottom end and a dry, less than fully extended and airy top end--and perhaps figure out pretty quickly that this isn't Class A/B amplification. But even a hardened audiofool like me came away from a few weeks spent with the SC-57 very impressed and enthused about the future of Class D in this application."

According to Pioneer, the SC-57's sound was perfected at the AIR Studios in London, known for recording full-orchestra motion picture soundtracks like "Inception," and Dire Straits' "Brothers In Arms" album. SC-57 prototypes were designed by Pioneer engineers to satisfy the standards set by the studio's engineers, and in doing so was awarded an "AIR Studios Monitor Certification." I don't have a clue what that means, but if Fremer liked the SC-57's sound, that's good enough for me.

If the Pioneer receiver's price is out of range, check out the cool-running Dayton DTA-100a Class T stereo amp ($100). It's a budget audiophile favorite.