It's a bit overbuilt because I decided to add a regulator circuit to my already built filter section.
Anyway, there is 670VAC between the plates of the full wave rectifier, a 12x4 tube, and then a stack of 5% zener diodes to provide a reference voltage of up to 380V. The output of the rectifier will never get that high, so the regulator mostly smoothes things out at whatever the rectifier tops out at.
I don't need all the large caps in the filter section, but it's already built and paid for.
here it is after it's warmed up