[4] From 1973 to 1974, he was employed at ESS and assisted Dr. Oskar Heil with crossover design, woofer selection, and final build cabinetry of audiophile, consumer grade loudspeakers.
[5] After graduating in 1974, he and René Besne founded high-end amplifier company Threshold Electronics on December 5, 1974.
Pass Labs produces the X series amplifiers,[10] which make use of the "supersymmetry" topology patented by Pass, to give extremely low distortion levels, and more recently the XA series of amplifiers, which advantageously combines aspects of the Aleph design with the "supersymmetry" technique.
[12] The SIT chip combines a square-law input character with a low impedance output to form the only solid-state gain device, which Pass claims, "behaves like a triode tube."
The point of the SIT is that it behaves like a triode but at lower voltages and higher currents, so it doesn't need a matching transformer to deliver power to 8 Ohms.
When brief bursts of musical energy occur, SITs react with rounded waveform tops instead of sharp and hard clipping of solid-state.