I have finished a cathode follower based preamp and the 0.01uf 1kv ceramic snubbing caps on the HV bridge rectifier diodes are buzzing (TDK CK45-E3AD103ZYNNA, sourced from Mouser so will be legit. but can be heard at 10 ft). Touching the caps (with something insulated of course) reduces the buzz a bit so I think it is them that are noisy. However, the audio circuit is dead quiet ie no hum and no buzz and sounds very very good.
It appears that I can use film caps instead of ceramics as snubbers ie bypass each of the diodes in the fw bridge.
I am using a 230ct transformer and getting 172 rectified dc across each diode (our ac runs a little hot ie around 245v so this is as expected). I am also getting a 40 volt drop on the 3900ohm B+ dropping/smoothing resistors (part of an LC circuit) which indicates I have approximately 10mA in the HV circuit (feeding 6dj8s).
My questions is, what voltage film cap should I use, specifically do I need 1kv which is what the ceramics are specced at or will something > 172Vdc, which I measure, suffice. I don't think I will get a film cap near 1kv to fit and I don't understand if there are serious voltage spike or other issues that occur in these circuits.
If I do need this high voltage rating I suppose I could drop uF a little to fit the space. I also assume I could do away with the snubbers completely if I get completely sick of the buzz. One final thought, would a smaller ceramic be less likely to buzz - the TDKs are nearly 1/2" across (11mm) or should I do something else?
thanks to all,
Nigel.
It appears that I can use film caps instead of ceramics as snubbers ie bypass each of the diodes in the fw bridge.
I am using a 230ct transformer and getting 172 rectified dc across each diode (our ac runs a little hot ie around 245v so this is as expected). I am also getting a 40 volt drop on the 3900ohm B+ dropping/smoothing resistors (part of an LC circuit) which indicates I have approximately 10mA in the HV circuit (feeding 6dj8s).
My questions is, what voltage film cap should I use, specifically do I need 1kv which is what the ceramics are specced at or will something > 172Vdc, which I measure, suffice. I don't think I will get a film cap near 1kv to fit and I don't understand if there are serious voltage spike or other issues that occur in these circuits.
If I do need this high voltage rating I suppose I could drop uF a little to fit the space. I also assume I could do away with the snubbers completely if I get completely sick of the buzz. One final thought, would a smaller ceramic be less likely to buzz - the TDKs are nearly 1/2" across (11mm) or should I do something else?
thanks to all,
Nigel.