Скачать или смотреть Vacuum tube voltage regulation

6lr8 and 0d3 based voltage regulator. You can theoretically use a lot of different tube options for this, as stated in the video it seems to be an incredibly tolerant design.

There's a Triode held below ground potential that takes voltage feed back from a divider circuit. This is fed into the pentode grid (you can use a Triode too) and that causes the output to feed or not feed. This will make for a fun bench supply, swing is about 80V(220V-300V) and I think it's probably something I can adjust a bit more depending.

http://www.radiomuseum.org/tubes/tube...
https://www.manualslib.com/manual/465...
http://www.pmillett.com/hv_bench_supp...