Thanks,
I'm just trying to figure out better means of applying DC filament power, than I have been normally using, including using switcher bricks. I kinda figured that combining tubes and SMPS bricks would be some form of heresy, and that the thermionic spirits would be displeased, but I found that even some of the "purists" who turn up their noses at any tube that isn't an original Western Electric, happily use switchers to feed their filaments.
Going one step further, I did run across a 300B SET design that got around the AC hum problem entirely, by using rechargeable batteries for filaments and B+ voltages. An elegant and expensive solution, to be sure :o
I probably have enough Li-Ion cells (recovered from discarded laptop battery packs) around to make one heluva B+ source, but being able to reccharge and maintain them properly would be a major problem, as they can't just be strung in series like NiCDs and charged up at high voltages. Each cell needs to be individually pampered, nurtured and fed Yellow_Light_Colorz_PDT_02
/ed B in NH