I first heard about Class-T amplifiers not from recording engineers or audiophiles, but from friends seeking my vaguely "professional" wisdom. I could not offer any advice, as I hadn't even heard of this technology. Both friends gave a similar description which definitely left me curious: a tiny, cheap amplifier that allegedly sounded as good as prohibitively expensive audiophile gear. I bought one right away. At the very least, I expected to have a trustworthy portable amp that I could conveniently use for remote sessions. I could also answer my friends' strange and nerdy questions. I had no expectations about its ability to sound as amazing as testimonials on the Web might imply, but I was curious.

Class-T technology was developed by San Jose-based Tripath, and technical details can be found on their website (www.tripath.com). While companies like Bel Canto Design and Audio Research have developed Class-T amplifiers with quality interconnects, circuit boards, and power supplies that sell for $3000-4000, I bought the small, plastic Sonic Impact model that first caught my attention for $30. It can run on batteries, but I powered it from my universal DC wall-wart.

As advertised, it definitely sounds better than any small, cheap amplifier I had ever heard. For remote sessions where size limitations on gear can be an issue, or for powering speakers to accompany an iPod or portable CD player, the Sonic Impact delivers fabulous quality. Despite some users' raves to the contrary, the Sonic Impact never impressed me quite as much as the three amplifiers that I currently own, which typically cost almost ten times as much. The Sonic Impact's transient detail and imaging generally exceeded the expensive amplifiers. Its weakness lay in its midrange performance, which I found sterile, sometimes in a distracting way. These sonic properties remained consistent across different combinations of speakers and preamplifiers.

For $30, the Sonic Impact is a compact, cheap amplifier that allows reliable, unfatiguing listening-an impressive and surprising accomplishment, even if, to my ears, it fell slightly short of its hype. I remain curious if $4000 Class-T designs, Sonic Impact's new higher-quality Super T ($130), or kit-style amplifiers from 41Hz, Bolder Cable, or Red Wine Audio might impress me more. Adding further confusion to the growing field, the Japanese company Flying Mole has introduced its own digital amplification technology that competes with Class-T amplifiers. ($29 direct; www.si-technologies.com)

Tape Op is a bi-monthly magazine devoted to the art of record making.

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