Pass Labs is a high-end audio company based in Auburn, California, United States, founded by Nelson Pass in 1991. PASS Labs has been developing prototypes of Class-A amplifiers with single-ended circuitry. Among the company's first products was the ALEF line of amplifiers with unique technology and design. PASS Audio developed SuperSymmetricTM technology, which is still used in its high-end products today. Pass Labs is dedicated to the design, processing and design of high-end amplifiers and preamplifiers.