5v333
Well-known member
If you search for allpass filters, youll prob get a opamp based circuit.
i have been wondering if its possible to make a solidstate APfilter and more so with a triode.
here is a cathode follower where both grid and cathode serves as inputs.
if there was equal signal on both grid and cathode, there would be no alternating current action through the triode.
if we RC couple the grid and direct couple the carthode there will be phase and amplitude difference where the filter has its pole.
so now we have difference and the triode will deliver AC current over the freq selection.
the gain will be no more then about 0.95.
the series input resistor in the cathode can be scaled so it forms a 0.95 factor voltage divider with the load/cathode resistor. i think by doing so the signal injected at the cathode will match the gain of the grid injected signal and CMRR will improve. if this is of any importance i dont know...
triode could be 12au7, B+ 400V, 22K load resistor, 620R cathode resistor.
havnt tried or simulated it.
why would anybody wanna do a SS APfilter?
it could be used for making a discrete CAPS network for ex.
your thoughts!?
i have been wondering if its possible to make a solidstate APfilter and more so with a triode.
here is a cathode follower where both grid and cathode serves as inputs.
if there was equal signal on both grid and cathode, there would be no alternating current action through the triode.
if we RC couple the grid and direct couple the carthode there will be phase and amplitude difference where the filter has its pole.
so now we have difference and the triode will deliver AC current over the freq selection.
the gain will be no more then about 0.95.
the series input resistor in the cathode can be scaled so it forms a 0.95 factor voltage divider with the load/cathode resistor. i think by doing so the signal injected at the cathode will match the gain of the grid injected signal and CMRR will improve. if this is of any importance i dont know...
triode could be 12au7, B+ 400V, 22K load resistor, 620R cathode resistor.
havnt tried or simulated it.
why would anybody wanna do a SS APfilter?
it could be used for making a discrete CAPS network for ex.
your thoughts!?