Over the course of his 30-plus years in high-end audio, Nelson Pass
's designs have never been far from the leading edge. In his first Threshold amplifiers he pioneered the use of dynamically adjusting bias and cascode circuitry; then, in the later Stasis models, he switched gears to the simpler approach of pure class-A. All were innovative designs, and among the very best-sounding amps of their time, but were just warmups for what was to come. In 1991, Pass Labs introduced the Aleph 0, a class-A amplifier that was a startling departure from conventional solid-state designs and combined design elements generally thought mutually exclusive: transistors, single-ended operation, and the ability to output 75Wpc into an 8-ohm load. Not surprisingly, the Aleph 0 sounded like nothing else, and became the basis for the widely acclaimed series of Pass Labs amplifiers that evolved over the next decade.