I just posted a couple of servo bias circuits at ABSE.
These are just for examining the principles involved.

Patrick Turner.

Patrick wrote:

Patrick,

I think decoupling the base with C to ground places the full Plate supply
ripple across the emitter resistor. This resistor determines operating
current of the differential amplifier.

The amount of ripple in all my amps is insignificant,
and usually less than 20 mV at the B+.
The resultant hum transfered to the grid bias supply is negligible.
The commoned emitter feed resistors on both schemas
could be divided into half the value, and an extra electro
placed in there to smooth out the ripple.
Notice the 10v zener to create the voltage reference in the SE bias control.
In the PP bias balance controller, the hum that is supplied to the common
emmiters
is in common mode, and is further divided down before reaching the output
grids
where any PS oise is applied in common mode.

Those schemas are just to show a principle applied, and further refinement
is possible.

Some engineers favour opamps, but I prefer high voltage rated bjts in tube
circuits,
to act as slaves to allow the tubes to do their thing better.

Patrick Turner.



Patrick

"Patrick Turner" schreef in bericht
...
I just posted a couple of servo bias circuits at ABSE.
These are just for examining the principles involved.

Patrick Turner.