Pass Laboratories, founded in 1991 by Nelson Pass in Auburn, California, is renowned for its high-end audio equipment, particularly amplifiers and preamplifiers. The company gained early acclaim with its Aleph series, which featured single-ended Class A designs using MOSFETs. In 1998, Pass introduced the X1000 amplifier, employing the patented SuperSymmetric™ topology to achieve exceptionally low distortion levels. This innovation laid the foundation for subsequent models, including the XA series, which combined aspects of the Aleph and X designs to deliver balanced single-ended Class A amplification. Pass Labs is also known for its commitment to quality, offering extensive after-sales service and support for legacy products. Their products are handcrafted in the USA, emphasizing durability and longevity.