The Pass A-40 Power Amplifier — Nelson Pass / 2000

FLATTERED BY THE opportunity to publish a project circuit, the designer is often beset by seemingly contradictory considerations. On the one hand, it is tempting to design a complex circuit as a demonstration of technical prowess; an amplifier with large numbers of esoteric components performing obscure functions. Such an amplifier might be a smorgasbord of electronic technique, featuring class A operation, cascoding, constant current sources, current mirrors, and extra-loop error correction. It would be fascinating to build and perhaps would also sound good. On the other hand, complexity is not a good end in itself and a much simpler circuit… More...

Ground Loops — Kent English / 2002

Your brand new component is hooked up, fresh from the box, and the fi rst time you power it up is a sonic disaster; it hums, it buzzes and in general sounds absolutely dreadful. Glaring at your equipment or dealer doesn’t help and twisting knobs only makes the noise worse; what now? From years of experience we fi nd that the vast majority of excessive noise in audio electronics can be traced directly to poor grounding techniques. While we recommend balanced interconnects on your audio components whenever possible, it must be understood that balanced interconnects address only the problems of… More...