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6L6GC / KT66 / 5881 tubes

The most common types of 6L6 tubes and their European equivalents used today include:

6L6GC - The popular 6L6 beam-power pentode was introduced by RCA in 1936 and culminated in the development of the 6L6GC tube in the 1950s. The higher rated 6L6GC can be used in place of any of its predecessors, including the metal can 6L6, coke bottle 6L6G, compact 5881, and straight-sided 6L6GA and 6L6GB tubes. It can also be used interchangeably with its European rival, the KT66.

5881 - The 5881 was introduced by Tung-Sol in 1950. This consumer version of the military spec 6L6WGB tube featured higher plate and screen dissipation ratings and greater resistance to shock and vibration. The 5881 can be used to replace any 6L6 tube type except the 6L6GC, KT66, or 7581, which all have higher power ratings.

KT66 - The KT66 was introduced by Marconi-Osram 1937. KT66 tubes have large clear or gray glass coke bottle envelopes. The KT66 can be used interchangeably with its European competitor, the EL37, and its American rival, the 6L6GC.

Other tube types in the 6L6 family include: 6L6, 6L6G, VT-115A, 6L6Y, 6L6GA, 6L6GAY, 6L6WGA, 6L6GB, 6L6WGB, 1614, 1622, 5932, and 7581. The 7027A tube has similar power ratings but with a different pin-out. 6L6 tube types can vary greatly in size, so check the clearances in your chassis if you plan to sub one type for another.

Comparison of
design maximum values for 6L6 tube types (pentode connection)

5881 6L6GC KT66
Max. Plate Dissipation 23 Watts 30 Watts 30 Watts
Max. Plate Voltage 400 Volts 500 Volts 500 Volts
Max. Screen Voltage 400 Volts 450 Volts 500 Volts

6L6 tube types in stock now

Scroll down to browse our current selection of vintage 6L6 tubes and burned in, tested, and precision matched new production 6L6 power tubes. Click "more info" for pricing, availability, and matching options.

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Tung-Sol STR 6L6GC reissue - premium matched
Tung-Sol STR 6L6GC reissue - precision matched
Price: $39.00
Tung-Sol STR 6L6GC reissue - precision matched
These new production Tung-Sol STR 6L6GC power tubes are built to the same Special Tube Request specs of leading 1960s amp manufacturers. These 30 Watt power tubes are rated for 500 Volts, making them a great choice for demanding guitar amp circuits.
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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