I appreciate your asking little questions about details which are not spelled out adequately. I will share my design considerations and trade-offs as requested. Of ocurse, if I am guessing out of my butt, I will also tell you of this. I do try to keep it to a minimum.

For the DC filament supply, you can filter and drop voltage through a few resistors, or regulate with something like an LM317. I learned obout those things with Google and the diagrams proviede on the packaging Radio Shack sold them in.

After a bit of wrestling with the unregulated stuff I am using in the new one, I do miss the adjustability of an LM317 with a pot in its voltage setting circuit. I also remember making a few mistakes with the first building with the LM317...so I suppose there is no free lunch, just different lines at the same register. We'll get there together, I'm sure of it. Especially if you keep asking questions.
regards,
Douglas