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...

Zen Amplifier Revisited — Nelson Pass / 1994

I must say that I have been very gratified by the response to the Zen amplifier from the last issue of TM. Since writing the article I have had an opportunity?to build another 25 copies of the amplifier, listen to it on a larger variety of loudspeakers, absorb criticism from the readership, and generally meditate on the project. Areas of criticism of the design all relate to the objective, measurable performance, but in addressing them, I found that the subjective performance improved with the measurements. All of the changes are performed without altering the original topology of the project amplifier.… More...