I would think i get about one and a half watts, maybe as much as two. I could get more by increasing the voltage but i seem the have enough. With 2A3 monoplates i get about 3 watts.
Just hooked up a large valve laboratory supply to play with voltages.......
I just changed the amp over to UX 250 globe from 45s and thought i post some hi res pictures for the interested. With the 1930 globes it is indeed sublime.
Another way to do it is use a high value choke to ground to bias the OP tube. This one would be perfecthttps://www.hificollective.co.uk/components/audio-note-chokes/choke-200.html450 Henries..... that's a beast Even at 20Hz the load only will be >50k but DC resistance = 2k, should keep the OP tube grid current happy. T
Ordered