Pass Labs was founded by the esteemed Nelson Pass in 1991. By this time Nelson had already built a stron reputation for his ground breaking designs, the early days of Pass Labs were saw Nelson working from his home, it was then that Pass developed prototypes of s single ended Class A amplifier design. The iconic Aleph 0 started shipping in 1992, It was a mono-block design rated at 70 watts into 8 ohms, and was unique in using three gain stages of power Mosfets including a push-pull output stage biased by a big constant current source. The amplifier operated as single-ended Class A up to its 70 watt rating and in push pull Class A at higher wattage.

Today Pass Labs manufacture an entire line up of amplifers to suit a wide range of budgets, leading up to the top of the line XS series of amplifiers including the master peice the XS Phono Stage which is simply jaw dropping.