QSC QSC Audio is a manufacturer of professional audio products, and are best known for their live sound products. Founded in 1968 by Patrick Howe Quilter, QSC is based in California, and they make amplifiers, signal processors and digital mixers. Founded:1968Founder(s):Patrick Howe Quilter Average User Rating 0 0 votes Please sign in to rate. Your Rating 0 Contact Phone Number: +1 (800) 854-4079 Address: QSC Audio Products, LLC. 1675 MacArthur Blvd. Costa Mesa, CA 92626 Email: firstname.lastname@example.org Online: History History coming soon!