Talk about a Scarlet Letter. The term class-D amplification, which describes PS Audio's new M1200 monoblocks, exists only because another amplifier innovation had already parked in the "C" space. Soon after appearing in high-performance audio gear, class-D became synonymous with "digital amplification" in part because, like early CDs, many listeners found the sound glary, hard, and unpleasant. Besides, class-D is related to "pulse width modulation" and requires a low-pass filter to block high-frequency pulses—that sure sounds digital. But they're not (see Bruno Putzeys sidebar).

I'm a sucker for materials, whether it's finishes for loudspeakers and other audio equipment, a shoe's fine, supple leather, a crisp cotton shirt, or a cozy cashmere scarf.

Apart from their inherent sensuousness, materials can make a difference in the sonics of audio components, especially loudspeakers.

Cavitation revolutionized record cleaning more than a decade ago, when Reiner Gläss's Audiodesksysteme introduced its original fully automatic machine. Mr. Gläss's innovative machine, which automatically spun the record in ultrasonically cavitated water, then dried it with fans, at first was plagued with reliability issues, and because it is sealed, it was not easy to repair.