I actually used GL KT77 in a pair of AES Six Pacs and V12r. I swap valves between the two. I really think the Ruby has the edge between the two but both are very good valves. EH greens EL34 are a good valve too.
Stay away from the cheapo Chinese generic. I found up to 20% failure rates and tough to match 6 valves per side. After a lot of burning in they are ok, but for joe blow..
6V6
KT-66
KT-77
6L6
6550
EL34
KT88
KT90
ALL these valves work quite well in that unit.. No problem at all. THAT amp is one of the best amps ever made.. I love mine and the sound is so easy to change..
4 coke bottle 6L6s in single ended mode.. about 17.5 watts per channel.. Mercy just pure heaven..
You can also just run 4, 8, or 12 valves. You don’t have to run all 12.
Two matched pairs of valves and you’re up and running. Very easy to voice WELL..
It’s very seldom I run more than 8 valves total. You just have to start from one end or the other and put 2, 4, or 6 in a row from one end or the other.. And bias up until you JUST get the health lights and back it off 10 degrees of 360.. IF you bias with a scope the actual watts per channel goes over 112 per side.. Without a scope about 100 WPC. 12 EL34s or KT88 in UL. Small planars love that amp in A/B push pull.
Mine is parked for the summer BUT late summer I’ll put it back into service with 8 6V6 matched Rubys. You should hear that little combo.
Then when it turns cold, 12 EL34. It’s how we warm the front room..
I’ve never tried less than 6 valves per mono block.. If it’s the same layout as the V12R that will work in them too.. I haven’t tried it on my AES 6Pacs.. I have some new parts.. I’m gonna give it a shot, this winter. I’ll post if it goes up in smoke.. :-)
Regards