by The latest update to the 100 Watt 6P45S tube amplifier is the measurements of frequency response from square waves and bandwidth measurements.
The prototype is now considered done as it has proved itself capable of outputting 210 Watt peak before clipping. At 100 Watt peak it have its -3dB points at 11 Hz and 72 kHz.
Looking at your schematics, I see that you are using transistors to bias the tubes. This really is not necessary as the tubes will self bias when putting a 1M resistor from the grid to ground and the cathode to ground through a resistor 1k to 3k. Then the stages will be self biased class A amplifiers.
My experience is working with tubes as a hobby for about 4 decades, and a MS in electronics. Tubes are not critical in bias as transistors are. Also the tube equipment is great to use during the winter as they are great room heaters. I have a 535 scope and many other kinds of equipment as well.
Hi Paul
It is not just bias, but balance the transistors is there for. Read the explanation in the start of the article.
Kind regards
Mads