Re: CT Filament transformer Don't go to the trouble of rewinding the transformer!!! CT isn't really necessary, but if you decide you need one put a couple of power resistors (say about 20 ohms) in series across the transformer and use the center of that pair for your center tap. Old scheme, used with potentiometer for "hum bucking" in audio amplifiers with directly heated cathodes (filaments, in other words). Ed Phillips