KT-77 vs. KT-66

They’ll sound different in different circuits. I’m running GL KT66 in my Dyna/VTA 70s, and prefer them over any of the 6CA7s and EL34s I’ve tried. Midrange and lower treble are clear and lush. Bass had more extension with the Nesstone 6CA7, but the KT66 only feed the midbass and tweeter from 80hz+, where they do extremely well.

All things being equal, KT66=6L6 w kinkless filament.  KT77=EL34 kinkless filament.  That being said, I prefer the Gold Lion KT77 over my Tesla, Svetlana, RFT, VEB and Psvane (the worst) EL34s.  KT77 has more of everything of the EL34 sonic signature.  
 

i have Sylvania 6L6 GBs and GCs, and Tung Sol 5881s.  Different sonic signature than EL34, less bass but more airy twinkling treble.  I don’t have KT66 (yet!) to compare, but going off KT77, if you like the 6L6 sound in your amp, you’ll love the KT66.  I’ve had excellent luck with Gold Lion new production from EH.  
 

My tube rolling amp is a Dennis Had Inspire KT88, best $2,000 SEP on the planet, IMO. Very revealing of tube changes.

Cheers

Thanks for the replies. I realize how much variance can come from amp, manufacturer, etc. and so trying it is the only way.

One thing which patterns these responses that helps me is that the KT66 is definitely going to differ a lot from KT-88's. That's the kind of nudge which helps me move ahead to try it.

@trivema My amp will *not* play a 6L6 so I don't know what it sounds like. 

KT = Kinkless Tetrode. So designed to remove the "kink" in the curve of the anode  characteristic in older designs. 

KT77=EL34 kinkless filament.

@noromance I think Bizarro World has a character named Kinkless Friedman to balance out our own.