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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 - 6 of 6 results
GE 6550 / 6550A - welded plates, matched pair
GE 6550 / 6550A - welded plates
Price: $249.00
GE 6550 / 6550A - welded plates
The 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 (52.1 & 54.9 mA) and transconductance (6200 & 6400 Gm).
Vintage Svetlana 6550B-3
Svetlana SED "Winged C" 6550B-3 - "clear top," precision matched
Price: $69.00
Svetlana SED "Winged C" 6550B-3 - "clear top," precision matched
These distinctive early 1990s Svetlana 6550B-3 tubes have side getters with no flashing on the top or sides. They were made at the SED SPb factory in St. Petersburg. Price includes extended burn-in and precision matching.
Svetlana
Svetlana SED "Winged C" 6550C - precision matched
Price: $89.00
Svetlana SED "Winged C" 6550C - precision matched
These Svetlana 6550C tubes were made in St. Petersburg in the early 2000s. The gold print on the glass has the "Winged C" Svetlana Electron Devices (SED) logo. Price includes burn-in and standard matching service.
Valve Art 6550A - matched pair
Valve Art 6550A - matched pair
Price: $149.00
Valve Art 6550A - matched pair
The Valve Art 6550A tubes in this matched pair have top and side getters with lots of flashing, with a similar look as the vintage GE 6550A tubes. The gold print on the glass has the Valve Art logo and reads "6550A O & J CHINA."
Valve Art 6550A - matched quad
Valve Art 6550A - matched quad
Price: $299.00
Valve Art 6550A - matched quad
The Valve Art 6550A tubes in this matched quad have top and side getters with lots of flashing, with a similar look as the vintage GE 6550A tubes. The gold print on the glass has the Valve Art logo and reads "6550A O & J CHINA."
Tung-Sol 6550 - black plates, matched pair
Tung-Sol 6550 - black plates, matched pair
Price: $299.00
Tung-Sol 6550 - black plates, matched pair
The rare 1958-59 Tung-Sol 6550 power tubes in this matched pair have welded black plates with no holes, metal collar bases (some corrosion). One tube has a repaired guide pin. They are matched for both current draw (49.4 & 47.8 mA) and Gm (96% & 93%).
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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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