I have a V12R I've listened to the oricinal V12 and then the I. I've heard 2 that have had the better Transformers, Caps and Hexfres installed.
I did all the upgrades along with cleaning up the factory rats nest for what passed as wiring. It is one of the most versitile, and easiest to voice amps I've EVER owned.
You can run either 2, 4 or 6 valves equal on both sides and bias using the health lights or 25-35ma per valve. They just have to be installed, all in the front or all in the back. 2, 4, or 6 valves. 3 or 5 per side won't work and no skipping. I BIAS at about 180ms with 6 valves per side.
I run everything but KT90 or 99.
6V6, 6L6, KT66, KT77, EL34, 6550, KT88, KT90, KT99
Stock Ruby EL34 are just perfet for that amp.. KT66 or 77s are next on the List.
Fat Bottle 6L6 are a real sweet sound too. I just run 2 per side of FB wonderful sound. About 15-20 watts in single ended mode, 30-35 in UL.
IF the 4 560mf filter caps haven't been changed or your not sure.. Change them no matter what.. Single best way to cool them down. I swapped at least 6 set of Carys. They all cooled right down.
I have a pair of Six Pacs that are fun too. I tricked them all out.. With copper foil caps throughout and a PS upgrade. I did a little resistor and cap swapping in the small valve section too.
Same valves in both. What fits in one fits in the other including most of the PS parts.. The caps are a little different on the signal and the power valves..
The mono blocks V12s are cool too.. I'd love to own a pair..
Regards