The first preamp stages run on +20, the mixer and limiter run on +16-17.
One of the things that eats my time up when I don't have anything else to do... ?!?!? is I'm writing a service manual for Thomas Vox solid state amps. I have a lot of data, enough to drown in, and getting it into book form is slow going. I have no illusion that I'll make any money from this, but I like the amps and hate to see them junked.