kt666's in 5f4?

[scole]

has anyone tried kt66 or kt88 in a 5f4 or other amp?

[Enzo]

KT666?

You'll have one devil of a time finding those.... even in New Jersey.

[MWJB]

Assuming that this is a repro amp, with a typical Fender BF/SF 50W style PT, KT66 should be fine, a little more heater current draw than 6L6 (1.3A vs 0.9A)...so overall, demand on the heater secondaries wouldn't be any more than 2x6L6 plus 6 12AX/T7 (3.5A total draw).

If it's an original/clone PT ...well if specs are available I'd check them first. If your B+ drops more than 20v and/or your heater voltages drop to less than 6.3VAC I'd get them out of there.

KT66 typically draw more plate current so rebiasing is a must.

The new Tung Sol claims to be a drop in replacement for 6L6 but no experience with this tube & not seen any data for it.

KT88, like 6550, draw twice the heater current of a 6L6, so either you really want a 100W PT (5A 6.3VAC supply absolute minimum, 6A or better would be good) or an auxilliary 6.3VAC transformer. Don't use a GZ34 with a pair of KT88, use SS or 5U4GB.

In fact, unless you know that you're going to like them and have tried them in something similar, I'm not sure that I'd bother with the KT88s.

[scole]

kt66 in a 5f4

sorry for the type-o, im using an allen power transformer wich is designed to handle el34's so it should be ok. im just so curious about kt66/kt88 i want to try them in something anyway. since i built the 5f4 for el34's im sure the tranny can handle them.

[Jammin'John]

KT66's

I'm runnin' a pair of Shuguang's in a Low Power Tweed Twin as we speak.
They have also been in a 5E5a with great results.
They look fantastic in a tweed.
Big tube with brown base.

JJ