SO I am trading my Marshall DSL100 for a '95 Marshall JTM45 reissue. I think this is a screamin deal because JTM45s are generally more expensive. BUT... the guy told me the tubes are original. Then, he told me that he once tried putting other tubes in it, just for kicks. I don't know what he put in there... but, if he put an EL34 in a 5881 socket, is it toasted? Is he ****ing me over?
Don't they come with EL 34s?
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I don't think it would work if the amp isn't designed to do that.

The pin wiring for the tubes are different. 5881's aren't exactly 6L6's, they're biased fairly different.
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You should be able to run KT66's which imo, sound much better than el34s. These are what are run in the original Marshall JTM45s, and sound amazing. I use these in my amp and honestly have no clue why Marshall uses 5881s in theirs.

Technically you should be able to run el34s in a JTM45. I don't think it would damage the transformers, they draw less current. But there is a slight difference in how the pins are wired on the el34. You may need to switch some wires around in there to operate them.

Oh but I fully endorse the JTM45. its an amazing amplifier. I hope you like your amps loud.
Last edited by al112987 at Aug 12, 2008,
i don't want to put a different type of tube in it. the guy who owns it now did and tried it without converting or biasing. i just want to know if that damaged it.
Go and try it. See if it works and everything, don't be afraid to turn it up loud either, make sure everything works. Technically, nothing should be wrong with the amp. The bias is set so the tubes operate correctly, at worst, he could have fried his el34s. However, part of me just feels like if he didn't rewire anything, the amp would not work correctly running the el34s. The pin arrangement is different on el34s than 5881s.

Either way, try it, if you like it, and it works, buy it and install kt66 tubes (I'm so not kidding about this, running 5881 tubes in there is blasphemous). Vintage amp circuits are very serviceable. If I learned anything from building my JTM45, is that its very hard to permanently **** something up. At WORST you blow one of the transformers, which sets your back a couple hundred, and is actually very hard to do as long as you are smart with how you're using your amp.
Last edited by al112987 at Aug 13, 2008,