6L6 Guitar Amplifier Power Valve (Alt 5881 / KT66)


6L6 Guitar Amplifier Power Valve (Alternatives are 5881 and KT66) is a beam tetrode power valve (vacuum tube) introduced by RCA in July 1936. At the time Philips had already developed and patented power pentode valve designs, which were fast replacing power triodes due to their greater efficiency. The beam tetrode design of the 6L6 allowed RCA to circumvent Philips’ patent. The 6L6 has had one of the longest active lifetimes of any electronic component, more than 70 years. The 6L6 valve was designed by Marconi and introduced by RCA under licence. RCA introduced the 6L6 to the market followed a year later by the KT66 made by Marconi.

You can buy the 6L6 Guitar Amplifier Power Valve below however it is likely you will need to buy a 6l6 matched pair or a 6l6 matched quad to ensure your valve guitar amplifier works correctly this is due to the circuit design. You can also consider buying a complete guitar amplifier replacement valve kit. Use the links at the bottom of the page to find your valve or amplifier.

Buy the 6L6 Guitar Amplifier Power Valve (Alt 5881 / KT66)

£27.49
in stock
1 new from £27.49
as of 20/10/2020 05:04
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£28.59
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1 new from £28.59
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£30.79
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1 new from £30.79
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£40.73
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1 new from £40.73
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£48.00
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2 new from £48.00
as of 20/10/2020 05:04
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Matched Sets of 6L6 Valves

More About the 6L6 Guitar Amplifier Power Valve

RCA’s first version was an early octal base tube. Like most with this base it had a metal, rather than glass, envelope. Later versions, including the 6L6G, 6L6GA, 6L6GB, 5881, 5932, 7027, and the final version 6L6GC had glass envelopes, which made cooling easier. The specification of the 6L6 Guitar Amplifier Power Valve series was gradually pushed upwards by adding more design features. The original metal version was rated for 19 watts while the later 6L6GC is usually rated for 30 watts. High transient voltages on the 6L6 anode can cause a flash-over between pins 2 and 3 on the octal base.

In vintage valve guitar amplifiers, this flash-over problem sometimes occurs if the amplifier is operated without the speakers connected, causing the self inductance of the output transformer primary winding to generate high voltages when the current changes due to the applied signal. For this reason the speaker terminals of 6L6 tube amplifiers are sometimes short-circuited by a switching 6.3 mm jack when the speakers are disconnected.

The 6L6 can be found in many guitar amplifier designs however it appears mostly on Fender and Peavey amplifiers. As of 2012 the 6L6 (KT66) Power Valve for Guitar Amplifier version was still being manufactured and used, primarily in guitar amplifiers. Manufacturing continues in Russia, China and Slovakia.

Alternatives to the 6L6

  • KT66 – The MOV alternative version which is lower power at 25w
  • 5881 – This is used as a 5881 matched pair or 5881 matched quad
  • 6L6-WGB – The “W” in the code, as in 6L6WGB, identifies the tube as designed for mechanically rugged environments, such as military or airborne use.

More Guitar Amplifier Valve Links

  • Buy Matched Sets of Guitar Amp Valves
    • Matched sets of pre-amplifier and power output valves to ensure the maximum performance from your amplifier.
  • Buy Full Guitar Amp Re-Valve Kits
    • The best way to get the best from you guitar amplifier. By changing all of the valves as a complete set maximum performance from the amplifier can be assured. Changing individual valves can be a false economy as the one weak link in the chain will affect the overall performance.
  • Look Up Your Guitar Amplifier
    • We have kits available for most guitar amplifiers. Use the link above or the SEARCH feature to look up your amplifier.

Is your Valve Guitar Amplifier not performing like it did when new? Has the output sound begun to degrade and break up? Are you experiencing additional noise and distortion? If yes, then it is time to consider replacing some or all of the valves in your guitar amplifier. Guitar amplifier valves (or tubes as they are known in the USA) are robust and will work for many hours. Performance will be affected by mistreating them or allowing them to overheat. Generally the performance of vacuum tubes starts to degrades with the amount of time they are used and up to 1000 hours is typically the optimum life of a valve or tube. If the performance of your amplifier is failing then it is likely that some or all of the valves need replacement.

When replacing guitar amplifier valves it is best to use matched pairs as this will ensure the valves last as long as possible with the best sound quality. We have a full range of replacement guitar amplifier valves and matched sets available for the most popular amplifier types – see the links above. Read our Guide to Replacing Guitar Amplifier Valves