Solid State Power Amp Reviews

It was a dark and stormy night. A biting, cold wind cut through Sam's skimpy jacket; ice crystals clung tenaciously to his bushy moustache. As he approached his front door, visions of a toasty-warm, Krell-heated listening room softened the chill. He could feel the glow already; his Krell amp had been on all day, awaiting his return.

One of my favorite parental duties is dispensing advice that's calculated to make me sound wiser than I am. Among those pearls: Every so often you should change your point of view—your philosophies—just to see if your opinions can stand the strain. In doing so, you may discover a few things that are better than you expected them to be!

James">http://blog.stereophile.com/ces2009/now_thats_what_i_call_music">James Bongiorno, the engineer behind the Sumo Andromeda, has enjoyed a long and colorful career as an audio amplifier designer. He has cast himself at times as an enfant terrible, exploding at audio critics and running scandalous advertisements (footnote 1). His best-known amplifier is the Ampzilla, produced by Great American Sound, but he also designed the Dyna 400. Currently Jim is living on a boat and serving as part-time consultant to the Sumo Company.

A decade ago, many predicted that amplifiers with switching or class-D output stages would come to dominate high-end audio. In a post–Peak Oil world in which the price of energy would always continue to rise, a class-D amplifier's very high efficiency in converting AC from the wall outlet into speaker-driving power would be a killer benefit. Although a conventional push-pull class-B amplifier has a theoretical efficiency of 78.5%, which would seem usefully high, this efficiency is obtained only at the onset of clipping; the need for the output devices to carry a standing bias current reduces that efficiency considerably, typically to around 50%. Class-A amplifiers are even less efficient, with a maximum of 25%; ie, three times as much power is dissipated by the amplifier as waste heat as is used to drive the loudspeaker (see "Sam's Space" in this issue).

Some time ago in these pages, Anthony H. Cordesman observed rather ungraciously that the whole line of Hafler electronics "could do with reworking." This was interpreted by many readers—including the good people at the David Hafler Company—as meaning that AHC felt the entire Hafler line to be mediocre. In fact, he does not. (He had given a Hafler product a positive review a few issues previously.) Tony's comment, however, did express a sentiment that most of us at Stereophile have shared for some time: a feeling that Hafler products had slipped from the position of sonic preeminence which they enjoyed during the 1960s and '70s to one of mere excellence in a field where only preeminence is acclaimed.

In Greek mythology, Atlas was the Titan who supported the heavens—although he's more commonly shown supporting Earth itself. (Funny thing, that: the globe he was always shown supporting actually did once represent the cosmos, but at some point became the Earth.) According to Hygenus, Atlas was the son of Aether, the personification of the sky and heaven, and Gaia, the personification of the Earth. Atlas was brother to Prometheus (foresight), Epithemius (hindsight), and Menoetius (a warrior whose insolence got him smitten by a lightning bolt from Zeus, resulting in a name synonymous with "ruined strength").

When I first laid eyes on the Paravicini M100A monoblock power amplifiers at the Consumer Electronics Show in January 2001, an audiophile in the room squinted at my badge and cried out, "Hey, J-10, these amps have your name written all over 'em!"