Solid State Power Amp Reviews

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!

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).

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").