A decade ago, many predicted that amplifiers with switching or class-D1 output stages would come to dominate high-end audio. In a post&#150;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%; <I>ie</I>, 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).

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).

<B>Neil Young: <I>Official Release Series, Discs 1&#150;4</I></B><BR>
Reprise 519173-1(4 LPs, Limited Edition Vinyl Boxed Set). 2009. Neil Young, David Briggs, Elliot Mazer, Jack Nitzsche, Henry Lewy, prods.; John Nowland, reissue eng. AAA.

I may have had 4000 LPs and a perfectly wonderful <A HREF="http://www.stereophile.com/turntables/1103linn">Linn LP12</A> turntable, but I could go for weeks on end without listening to a single LP. But I still thought of myself as one of the vinyl faithful, even as I rationalized my digital-centric listening tendencies. I loved analog <I>in theory</I>&#151;I just couldn't bring myself to listen to it all that much.

Corrina sent me a link to this video for "70 Million" by Hold Your Horses, a band I know nothing about. It must have been so much fun to make this.

BluePort Jazz's catalog of 15 titles, recorded in jazz clubs and studios by Jim Merod, is now downloadable in lossless FLAC format from the <A HREF="http://www.houseoflinn.com">House of Linn website</A>. Merod&#151;a PhD professor, an author of numerous books, a music critic for <I>Enjoy the Music.com</I>, and an equipment reviewer for <I>Positive Feedback Online</I>&#151;is known for recording with as few microphones as possible and mixing everything live to two tracks in high-resolution (24-bit/96kHz) PCM format.