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Pass Labs Introduction

Nelson Pass was born in Massachusetts in1951 and grew up in northern California. He received a degree in Physics from UC Davis while working for ESS, a loudspeaker maker known for the “Heil Transformer”. He co-founded Threshold Corporation, and served as its President from 1975 to 1991 selling his interest in 1987. In 1991 he founded Pass Laboratories, where he is to be found now.

Mr. Pass specializes in amplifiers and holds seven audio patents, six of which are amplifier circuits. He developed the first dynamically biased Class A circuit in 1974, a fully cascade audio power amplifier in 1976, and the “Stasis” amplifier in 1977. At Pass Labs he helped popularize solid state single-ended Class A power amplifiers and developed the very successful Aleph series. These were eventually replaced by the “Super-Symmetric” circuit which exploits the properties of symmetric balanced circuits and symmetric feedback to obtain low distortion and noise from very simple circuits. The first such amplifier was the X1000, which delivered 1000 watts at low distortion with only two stages: a differential input pair of transistors and a large bank of output followers.

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