EL-34s in a Fifty/Fifty? KT77s?

[joey_truelove]

I've heard about some guys that use this valve instead of the 6L6GC for which the Fifty was designed. Would it be safe to run a pair in one channel, do you think, and if so: how do I modify the amp?

I read somewhere that the KT77 would be a direct replacement for the 6L6 in that the output impedance is the same. I'd still need to set the bias and pray the PT would hold, though.

Cheers!

 

[Paul Secondino]

KT 77's are a replacement /alternative for El34's rather than 6l6's. Maximum plate dissipation on the KT77 is 25 watts just like a EL34 but plate dissipation on a 6l6 is 30 watts.

You can just put the EL34's into the amp but they require more filament current than the stock circuit provides and they will run very very cold and probably sound harsh and sterile

I don't think you will want to run EL34 or KT77in this amp without modifying it quite a bit to optimize the power supply to run with those kind of tubes.