Tung-Sol was a high quality manufacturer of vacuum tubes based in Newark, New Jersey. In the 1920's Tung-Sol began manufacturing vacuum tubes. They worked to produce consistently high-quality tubes for use in military and consumer goods. They developed sophisticated, statistically-based quality control and production methods. This laboratory-like atmosphere earned Tung-Sol vacuum tubes a reputation of having some of the best metallurgy and chemistry resulting in extremely stable and repeatable production. In 1955, Tung-Sol revolutionized the audio world by creating the 6550 vacuum tube. The 6550 was developed for Hi-Fi, but due to its reliability also found service in avionics. The Tung-Sol brand name is now owned by New Sensor Corporation, which is the same company as Sovtek, Electro-Harmonix, Mullard and Gold Lion.