I built this last night, the board was pre-built, so really I just did
the mechanical stuff and wired it up. I followed Ed Brown's
post and tried a 6AV5GA, in Ultralinear mode. It's a standard
g*s*g board, with a 1K grid stopper to the tube socket, and the
cathode lead from the g*s*g's test points. The screens are connected
to the taps on the Edcor XSE15-8-5K output transformers.
It sounds really good, I'll crank it up later and see what it can do.
At about $ 3 per tube, they definitely give the 6B4G's a run for the
money.
This amp is a "convertible" and can quickly be changed to 6B4G's,
and with a socket and/or resistor change, to 6A3's or 300B's.
Bigger/More pix at http://tmamps.com