If I recall correctly (it's been many years since I last used "vacuum-state devices"), the center tap on filament transformers was normally connected to chassis ground to minimize mains frequency "hum" being induced in sensitive, low-level signals. Since the filament transformer only supplied current to the tube filaments, no current flowed through the center tap.Merlin Blencowe in this Tube Preamp book says that no current flows in the center tap of a 6.3 v filament transformer. Each leg to the center tap measures 3.25 vac. Why does no current flow in the center tap? I used to know, but I've forgotten.
by Jake Hertz
by Duane Benson
by Duane Benson
by Aaron Carman