5881 tubes
Hello Skip. Can I use 5881 tubes in place of 6L6’s? Can I do it in any amp? Thanks!
Thank you Skip!
Thank you again for your info Skip. Another question for you...
Premier Guitar article says...
https://www.premierguitar.com/articles/Everything_You_Ever_Wanted_to_Kno...
"Rarely seen for many years other than in vintage amps that carried them (notably early-sixties Marshall JTM45s, following their brief use of 5881/6L6s originally), the KT66 (pictured at right) is a direct substitute for the 6L6, but really has a character all its own. This tube of European origin is a little bolder, firmer, and fatter than its American cousin, and can put out a little more volume. A few good recent reissues of this tube type have led some amp makers to design around it again, and Dr Z’s Route 66 is one example of a popular boutique amp that takes advantage of the KT66’s potential."
If I can fit these suckers in an amp, can I use them?
Thank you again.
Great question, Dave! As with the 5881, the answer is basically yes. The KT-66 is interchangeable with a 6L6. In a cathode-bisaed amp , no re-biasing would be needed. In a fixed-bias amp (like a 4X10 Bassman) it would be best to have the bias checked when changing power tubes - the KT-66s may need an adjustment. The only other consideration (as you mentioned) is size. The KT-66 is physically larger and may not fit in every amp.
The KT-66 (and KT-88) were originally made in England by the Genalex company. Like the 5881, they were marketed as an "upgrade" 6L6 tube and are interchangeable with any 6L6. The original Genalex KT-66 is certainly a fantastic 6L6, especially for hi-fi use, but NOS examples cost hundreds of dollars EACH. Every current-production KT-66 is actually a "reproduction" of the original KT-66 and is made in China, Russia, or the Czech Republic. That said, if you dig the tone, feel free to use them in any amp that requires a 6L6.
Fantastic, thank you very much for the detailed answer, as always Skip.
Hello Dave- Great to hear from you!
In olden times (the mid-fifties) the 5881 was introduced as a high-performance version of the 6L6 made by either Tung-Sol or Sylvania. They were a direct replacement that could be used in any circuit that used a 6L6.
As far as current-production goes, the Sovtek-brand 5881 has been proven to be a durable, good-sounding tube.
If your amp is cathode-biased (like your old Masco and Rad-O-Lek amps) you are absolutely safe to swap out a 6L6 for a 5881. In a fixed-bias amp (like a tweed Bassman or Super Reverb) it would be a better idea to have the tools and skills to check the bias any time you are swapping power tubes.