Tubes Asylum

Posted by JJ Triode (A) on March 24, 2014 at 14:22:38

In Reply to: RE: How important it is to have the voltage of the filament being elevated ? posted by 6bq5 on March 24, 2014 at 10:29:17

…not increase the voltage difference between the two ends of each filament. Likewise, I think by "across" Mike Samra means you connect one resistor from each side of the filament circuit to a DC voltage, to create a virtual center tap. If the filaments are referenced directly to ground, the maximum cathode to filament voltage rating might be exceeded in some circuits, so you raise the filament average potential to some higher DC value, closer to where the tube cathodes are running. This can arise e.g. if you have a cathode follower, where the cathode may ride at a couple of hundred volts DC.