6550 / KT88 / KT90 / KT120 tubes
The most common types of 6550 tubes and their European equivalents used today include:
6550 - Tung-Sol developed the first 6550 tube in 1955. The design was based on the 6L6GC tube with higher power ratings, and featured a coke bottle shaped envelope like the European KT66 tubes. GE and Sylvania later developed uprated 6550A tubes with straight-sided glass. The 6550 can be used interchangeably with its European rival, the KT88.
KT88 - Marconi-Osram Valve Co. introduced the KT88 in 1957, and its Genalex Gold Lion KT88 became known as "King of Power Tubes." The KT88 is a larger version of the KT66 that features higher power and very low distortion. The KT88 can be used interchangeably with its American rival, the 6550.
KT120 - In the spirit of Tung-Sol’s creation of the 5881 and 6550 power tubes, New Sensor Corporation released the KT120 under its Tung-Sol label in 2010. With a plate dissipation of 60 watts, the Tung-Sol KT120 is the most powerful tube in the 6550/KT88/KT90 family. Please see our notes about substituting KT120 tubes for 6550 and KT88 tubes.
Comparison of design maximum values for 6550 tube types (pentode connection)
|Max. Plate Dissipation
|Max. Plate Voltage
|Max. Screen Voltage
6550 / KT88 / KT120 tubes in stock now
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TC Tubes specializes in precision testing and matching of vintage and new production vacuum tubes for guitar & bass players, audiophiles, and DIY tube audio enthusiasts. Our website features secure payment options and fast, convenient shipping around the world.
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