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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)

6550 KT88 KT120
Max. Plate Dissipation 42 Watts 42 Watts 60 Watts
Max. Plate Voltage 660 Volts 800 Volts 850 Volts
Max. Screen Voltage 440 Volts 600 Volts 650 Volts

6550 / KT88 / KT120 tubes in stock now

Scroll down to browse our current selection of vintage 6550 tubes and burned in, tested, and precision matched new production 6550 power tubes. Click "more info" for pricing, availability, and matching options.

Displaying products 1 - 10 of 10 results
Genalex Gold Lion KT88 reissue - premium matched
Genalex Gold Lion KT88 reissue - precision matched
Price: $57.00
Sale Price: $51.30
Genalex Gold Lion KT88 reissue - precision matched
These new production Genalex Gold Lion KT88 power tubes are based on the original Marconi-Osram Valve Co. made in the 1960s. Price includes extended burn-in and precision matching.
on sale
Sovtek 6550WE - premium matched
Sovtek 6550WE - precision matched
Price: $29.00
Sale Price: $26.10
Sovtek 6550WE - precision matched
The Sovtek 6550WE features thicker plates, improved heat dissipation, higher transconductance, and increased linearity. The result is higher output power, greater headroom, and superior tone. Price includes extended burn-in and precision matching.
on sale
Tung-Sol KT120 - premium matched
Tung-Sol KT120 - precision matched
Price: $48.00
Tung-Sol KT120 - precision matched
With a plate dissipation of 60 watts, the Tung-Sol KT120 is the most powerful tube in the 6550/KT88/KT90 family. A matched pair in push-pull configuration can deliver 150 watts of power. Price includes extended burn-in and precision matching.
Ei KT90 - Type I, precision matched pair
Ei KT90 - Type I, precision matched pair
Price: $197.00
Ei KT90 - Type I, precision matched pair
The Type I Ei KT90 power tubes in this precision matched pair were made in the former Yugoslavia. They have welded gray plates and dual O getters. Type I KT90 tubes can be used as substitutes for 6550 / KT88 tubes in amps that have enough bias range.
GE 6550 / 6550A - crimped plates, matched quad
GE 6550 / 6550A - crimped plates, matched quad
Price: $394.00
GE 6550 / 6550A - crimped plates, matched quad
The late 1970s GE 6550A power tubes in this premium matched quad have gray plates, 3 getters, metal collar bases and 188-5 factory code (Owensboro, Ky). Tubes test as new and are precisely matched for both mA and Gm. While supplies last!
GE 6550 / 6550A - welded plates, matched pair
GE 6550 / 6550A - welded plates, matched pair 1
Price: $179.00
GE 6550 / 6550A - welded plates, matched pair 1
The late 1970s GE 6550A power tubes in this precision matched pair have gray plates, 3 getters, metal collar bases, and 188-5 factory code (Owensboro, Ky). Tubes matched for both current draw (60.8 mA & 61.8 mA) and transconductance (103% & 106% Gm).
GE 6550 / 6550A - welded plates, matched pair
GE 6550 / 6550A - welded plates, matched pair 2
Price: $179.00
GE 6550 / 6550A - welded plates, matched pair 2
The late 1970s GE 6550A power tubes in this precision matched pair have gray plates, 3 getters, metal collar bases, and 188-5 factory code (Owensboro, Ky). Tubes matched for both current draw (47.6 mA & 47.6 mA) and transconductance (96% & 96% Gm).
Sylvania 6550 - matched pair
Sylvania 6550 - matched pair 1
Price: $197.00
Sylvania 6550 - matched pair 1
The 1970s Sylvania 6550 power tubes in this matched pair have welded gray plates, 3 getters, and metal collar bases. The green print on the glass has the PhilipsECG logo (partial). Click "more info" for test restuls.
Sylvania 6550 - matched pair
Sylvania 6550 - matched pair 2
Price: $197.00
Sylvania 6550 - matched pair 2
The 1970s Sylvania 6550 power tubes in this matched pair have welded gray plates, 3 getters, and metal collar bases. The green print on the glass has the PhilipsECG logo (partial). Click "more info" for test restuls.
Sylvania 6550 - matched pair
Sylvania 6550 - matched pair 3
Price: $197.00
Sylvania 6550 - matched pair 3
The 1970s Sylvania 6550 power tubes in this matched pair have welded gray plates, 3 getters, and metal collar bases. The yellow print on the glass has the Magnavox logo (partial). Click "more info" for test restuls.
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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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