KT-77 vs. KT-66

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.

I’ve been playing both these tubes this week.  I have primalunas, both tubes are from gold lion, new production.  In my system the differences are very easy to hear.  The 66s have more top end emphasis, and perhaps a bit more transparent, though that could just be the added detail on top.  The 77s are warmer, more midrange emphasis.  The bass is about the same on both.  I could see some people saying the 77s were more natural sounding and the 66s more “HiFi”.  Overall I prefer the 66s.  I was told by someone at Upscale that the primalunas mate better with the 66s based on the amps’ transformers, but I don’t know any more about that.  Having owned the stock El34s, other El34s, and the 77s, I can say that the 66s were definitely a change in sound overall and I was glad I bought them.  What do the KT88s sound like?  I need to try those!