-with indirectly heated tubes and a power amplifiers, DC supplies for the heaters (both driver and output tubes) are often not necessity, especially with PP amps
-preamps, especially low-level signal types (mics, RIAA) usually need DC-powered heaters
-filaments in DHT-based power amps (power tubes) can be AC operated, but sometimes DC in needed, in SET low power amp + high efficiency speakers cases. Some people claims that AC sounds better, especially in comparison with simple/bad DC fillaments supply
-there`re several types of DC supplies - from simple, pasive types (CLC, CRC...) to the regulated ones. With IDHTs, simple series voltage regulators (transistors or ICs) are "good enough". But, with DHTs (where filament = cathode = signal path), probably more "refined" versions are in order (CCS, shunt regulation...)
-see, for example, some heaters/filaments and supplies article by Mark Kelly:

• http://www.members.iinet.net.au/~quiddity/audio.html

• http://www.lyricsbox.com/television-lyrics-prove-it-hzw4zzr.html

I can see the use for front end stages of a high gain amp, but I have not found them a requirement on my normal designs( that are high enough gain I can get by with no additional gain).
cheers,
Douglas

it's an interesting challenge, and I don't feel qualified to say what should be done. Matter of fact, it's your amp, work it out, and learn a lot along the way, and then build another...:)
cheers,
Douglas

I need to work out some details on the 813 amp. I have to rig a fairly high-power umbilical for those 2-channel beasties. That and getting the Peerless S-271-S output's wound, stacked and waxed...:) That big 5k should make for an interesting comparison between the stock Citation II iron. Fortunately Heyboer is in no rush to get those TX's underway.

The project is getting bigger and bigger, I suspect some of the issues will need solved as it is built. It will have 10VAC on its filaments.
cheers,
Douglas