Since the PP 2A3 project is moving ahead smoothly, the task goes to laying out a driver stage. The Sovtek 2A3's can run 300V into 6k6 a-a and remain solidly class A.

I have some small diameter TFE insulated co-ax, with a ridiculous capacitance per foot. A short length of this stuff looks like just the ticket. It is too bad it can't work for SE. Connect internal to the driver plate and the braid to the opposite 2A3's plate. I think I read that this is a WE trick from a looooong time ago. Either way, all ov a sudden a pentode can run a power triode.

For example a 12BY7A with a 10k plate load, a 300V plate supply, and 90V g2 will swing +/- 100V comfortably. With the PP circuit canceling the 2nd HD, this circuit will be quite clean. At this sort of swing, few triodes can compare, let alone in a single stage.

I have a bunch of ~20W 6k6 OPTx's...I smell a shoot-out/Tasting between them. The losers to eBay, the winner to the cloning winder. The nice side effect is that I'll be rid of a big pile of Iron when it's all over.
cheers,
Douglas