Paul Keinanen wrote:
On Wed, 29 Oct 2003 23:28:28 +0200, "Deos"
wrote:


the 6.3 VAC is ok ,no need to go into the fuss for dc.
dont take my word for it, after making the nice rig put some diodes on the
ac line and you will not see anythig special..


Using a single floating 6.3V secondary winding with a potentiometer
connected across it and the wiper connected to the ground and adjusted
for minimum hum should be enough.

This kind of system works quite well when you have a single high
sensitivity input (such as in a radio receiver), but if you have
multiple sensitive inputs (as in audio mixing consoles) you would need
a separate filament winding for each input tube, in order to be able
to adjust the filament balance without compromises. In such situations
a DC filament system would be simpler to implement.

Paul OH3LWR


Except for high gain AF stages, a center tapped filament winding with the
center tap grounded should be ok. Otherwise a resistor of a few hundred to
a few thousand ohms from each side to ground (resistors of identical value).
Use of a pot is probably overkill, but if you have one in the junk box and
room to mount it ok.