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.