What can I swap into a JTM 45?

[Reeltarded]

And still have the output matched? KT66 right now.

I am not familiar with output impedance on types other than EL34, but I have 6v6s, KT88s, 6550s and 6L6 on hand.

Size requirements make me want to go with some short 34s. I think I might swap OTs so I don't have to explain the offset to many peeps.

[sliberty]

I've used 5881's, which are essentially 6l6's. They worked really well in my JTM45, although I still preferered the KT66's.

[Reeltarded]

I have a pair of those too. I think I tried them in the BB combo this head used to be. Maybe they actually came in it.. yes. I think so.

[Firestorm]

Real 5881s are different. If you can afford those, you can afford GEC KT 66s. But I've found that JTM 45s also like Svetlana 6L6s (from St. Petersburg) biased hot.

[Phil_S]

I freely admit I have no frame of reference. I built a JTM45 some time ago in a donor chassis that had the tube sockets too close for coke bottle tubes and with iron from an Arkay FL30. I put a pair of cheap Chinese EL34B in it and I think it sounds quite good. I Keep thinking the donor iron and the speaker, ceramic Weber Blue Dog, contribute more to the tone than the tubes. I'd play this amp more than I do, but it makes the walls rattle (cheap '50's paneling) and I'm not home alone often enough.

[LeftyStrat]

I've swapped out the KT66's for EL34's and then mismatched the output impedance to get 3.3k reflected load.

[Phil_S]

I admit that I didn't think about impedance. The Arkay FL30 donor was an EL34 amp and I knew before I built the JTM45 that I didn't have room for KT66's. Also, at least one JTM45 schematic I was using indicate that some were "fitted" with EL34's. I just figured impedance was the same.

[LeftyStrat]

KT88's at 436V take 6k primary according to the data sheets. Close enough for rock and roll. No idea how it would sound.

[Reeltarded]

I am going to need more bias range