Vacuum Tubes for Audio, Music and Radio from BOI AudioWorks

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6L6 Guide

What is 6L6?

6L6 is a power output tube used in many mainstream guitar amps and audio amps. It was originally developed in America in mid 1930s. After almost 80 years, more powerful and improved versions are being produced by factories in Slovakia, Russia and China.

When to Replace?

Output power tubes generate a lot of heat, and this causes it to wear out. If your amp starts to sound a bit flat and thin, it's a good time to start looking at replacing the output tubes.

Not all 6L6 are Same

Just some of our 6L6 offerings! Since 6L6 has been in production for so long, there are several 6L6 tube types. While all 6L6 types are pin compatible with one another, electrically some 6L6 types are not interchangeable with another.

When you replace 6L6, you should make sure that you replace with the right type.

There has been many 6L6 variations, but the most common ones today are:

  • 6L6GC
  • 6L6GB / 5881
  • KT66
Each are covered in sections below.

Original Brands at much less

Are you looking for Groove Tubes 6L6? GT-6L6B is relabeled Sovtek 5881WXT. GT-6L6S is JJ 6L6GC respectively. We carry the same tubes with original brand that cost less.

You can make quick price comparison by clicking Quick Lookup in our 6L6 Category.

Enjoy 6L6 Choices

There is a large number of 6L6 tubes on the market today, and we carry over a dozen best sellers. Whether you have '65 Fender Deluxe Reverb or Mcintosh MC-240, we have the right 6L6 in stock for replacement or upgrade.

6L6GC - The big brother

6L6GC is the higher rated 6L6. It takes 500V on the plate and can dissipate 30W. Because of this, 6L6GC types can be used in place of other 6L6 types.

Best Upgrade 6L6GC

6L6GC tubes from BOI AudioWorks Tube manufacturers have come up with 6L6GC tubes that are step up from factory installed 6L6 tubes. These are solid, rugged tubes, and they provide sonics that go beyond factory installed tubes.

If you are looking to replace or upgrade the original 6L6 tubes, these are the go-to choices.

Best Value 6L6GC

If you are looking for direct replacements of factory installed 6L6, we carry the originals without the re-branding, keeping the price down. These tubes have solid build and are recommended if you are on a budget.

Best Boutique 6L6GC

We also carry 6L6GC tubes by boutique brands such as Ruby, Groove Tubes and Tube Amp Doctor. These brands mainly re-label tubes that are built at the same factory as other brands, but certain tubes are built specifically for them and we think they are worthy. These 6L6 are ideal for those looking for unique and special tone that you call your own.

Whether you are re-tubing worn 6L6s or upgrading for better tone, any of the above will sound great and do well in any amps calling for 6L6.

Remember, all our power tube sets include free burn-in for maximum stability.


TungSol 5881 Re-Issue has excellent tones 5881/6L6GB is the smaller brother to 6L6GC. They are smaller sized than 6L6GC, and rated up to 23W.

Use Tung-Sol 5881 Re-Issue if you are looking for that great 5881 tone, but make sure your amp calls for 5881/6L6GB and not 6L6GC.

If you are after that Tung-Sol 5881 tone in higher powered amp, try TungSol 6L6GC-STR.

Again these tubes can replace lower powered 6L6G, 6L6GB, 6L6WGB and 5881 types, but will not work in amps calling for 6L6GC.


Great KT66 selection at BOI AudioWorks KT66 was originally developed as European counterpart to 6L6GC. KT stands for Kinkless Tetrode.

KT66 has higher filament draw than a 6L6, and can handle more power. In audio application, KT66 are smoother sounding with great texture. In a guitar amp, KT66 gives more agressive voicing as demonstrated by Marshall JTM45 Bluesbreaker.

  • Genalex Gold Lion KT66
  • Beautifully constructed, with the looks of original GEC KT66. This is our favorite KT66.

  • JJ KT66
  • Heavy duty KT66 in KT88 form. This is a very rugged tube that can be pushed hard.

  • Tung-Sol KT66
  • Another KT66 in KT88 form factor. It sounds more like 6L6 than any of the KT66.

  • Chinese KT66
  • Faithful replication of original GEC KT66, and gets great reviews used in audio applications.

  • Groove Tubes KT66HP
  • Out of production, but KT66 Gold Lion makes an excellent replacement.


350B Tubes at BOI AudioWorks 350B deserves a special mention. Original 350B was a 6L6 derivative made by Western Electric.

There is now a very good Chinese reproduction Valve Art 350B with great original looks and excellent sonics. This tube is very popular with HiFi and DIY enthusiasts.

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