Cascode Amplifier Design — Nelson Pass / 1978

Lowering distortion in power circuits without compromising their transient response remains a primary problem for designers of audio power amplifiers. Until fairly recently, the favorite technique for removing distortion components in linear amplifiers was to cascade many gain stages to form a circuit having enormous amounts of gain and then using negative feedback to control the system and correct for the many errors introduced by this large number of components. While the sum of these components' distortions may cause large complex nonlinearities, the correspondingly large amounts of feedback applied are generally more than equal to the task of cleaning up… More...

Son of Zen — Nelson Pass / 1997

The Zen has proven to be a popular and enduring do-it-yourself amplifier. The design addresses the audiophile's enthusiasm for singleended amplification, but is even more interesting for its exploration of the performance available at the extremes of simplicity, having only a single gain device. Judging by the mail, more than a thousand of them have been constructed, not including a couple of commercial rip-offs. Incoming mail is an excellent barometer of interest and taste among the readers. Letters suggesting design improvements provide the direction and the excuse to proceed with the Son of Zen. It responds to the following common… More...