Posted by Damir [ 213.202.86.235 ] on August 03, 2006 at 14:40:22:
In Reply to: Fiament choke and filter scheme??? posted by Norris Wilson on August 03, 2006 at 11:49:39:
My experience - in my PPP monoblocs both power tubes and a driver heaters are powered with 6,3V AC. With proper bias adjustment (PP cancelation) there`s no hum in the speakers I can hear - period. 
It requires proper (star) grounding, and (twisted) heater wiring layout, of course. Preserve the same phase (heater wire) for both PP tubes pins 2, and another phase (wire) for both tubes pins 7 (assuming "normal" octal power tubes - 6L6, EL34, KT88..., but the principle is the same).
Easiest with different heater wire colors, for example - pink and yellow... 
IMO - only if you can`t get low enough hum with AC (I doubt it ), try DC heating...IMO, IME, YMMV, and all of that...
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