In Leaving Class A, an article by Nelson Pass about Pass Lab’s design philosophy, he asks readers to imagine that “two transistors are runners in a relay race and the [electrical] signal is the baton they carry. In a real relay race, the runner receiving the baton begins running before the hand-off, which is made with the runners at speed. The runners who hand over the baton at a dead stop operate at a severe disadvantage.”
As it is with runners, so it is with amplifiers. Leaving Class A describes in clear, vivid prose the lengths to which Pass Labs goes “to build simple amplifiers that are distortion free” and “that sound as good as possible.” The article also demystifies differences among amplifier types — Class A, B, AB and push-pull — and explains how design elements like output current and bias affect performance, and why Pass Labs amplifiers are unlike most others on the market.