Cathode bias is all you need unless you don’t want distortion (which of course they didn’t. 8^)point I was trying to make is that more (possibly twice) power could have been available had more modern design methods such as different classes (A, A/B, B) been implemented. there were no silicon diodes in 39 and selenium devices were too large at that time to warrant practical fixed bias supplies to allow for these different classes...
I ran across a lot of selenium rectifiers when I first started playing with electronics in the late 60s. I think the last one I saw was ~15 years ago- and it was a big honker in a bias supply! The owner asked me to replace it with something less toxic...
Wishing all you T-Birders a happy and much better New Year 2021
