[sdiy] tube ladder

Tim Ressel madhun2001 at yahoo.com
Sun Jun 23 20:51:51 CEST 2002

Okay, I'm trying to understand all this. But something
does not sound right. When using an CA3080 for a
variable filter, the aspect of the 3080 that is called
into play is its CURRENT output. You take a 3080 and
put a cap to ground on the output and you make a
filter. By changing the 'gain', you vary the amount of
current that flows into the cap, thus changing the
center frequency.

Now to use a tube to do this, how would that work?
There is DC current flowing through the tube plus a
little AC current from the signal. But the plate R
turns that into voltage. If you put a cap from the
plate to ground, you just shunt the voltage variations
to ground.



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