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In Reply to: RE: recommended replacement for 1N4007 diodes.. posted by Michael Samra on July 21, 2014 at 21:55:11
Mike,Hope that you are feeling better. A question or two or three. What exactly is the function of bypass caps, in a typical 4 diode bridge? Like a traditional 4 x 1N4007 or UF4007 setup?
I've seen them used in multiple diodes per leg setups, to even out voltage distribution across the series diodes.
The inline resistor --- before first filter cap to help switching noise --- by altering the time-constant, seems reasonable. I don't quite understand how bypass caps helps switching noise.
Anyhow, I find UF4007 or UF5408 diodes with a well thought out PSU adequate for a quiet power supply. No bypass caps needed.
Edits: 07/22/14 07/22/14Follow Ups:
Steve
Ths bypass are in there to suppress switching noise from the diodes entering the circuit.Being the switching noise is at a particular frequency,it is very important to get the right value because if it's too large,it can raise the noise level even more.
Wheezer did a lot of research and testing on this and when he published the noise waveform out of the hexfreds,I no longer use those diodes on my application other than maybe a doubler circuit.
Honest amplification is better than excessive 2nd order distortion anytime.
Edits: 07/23/14
Thanks, Mike. JOC... what does this "switching noise" sound like? Is it in the audible frequency range? Is it possible to shift this noise to a frequency which is more harmful, by using the wrong valued bypass caps?In most amps I've seen, the main PSU diode bridge and bias diodes are removed from the main circuit board. My understanding is that RF noise generated by the rectifier board can be picked up by the main board. I'm not sure if this applies to modern fast-switching diodes, or not. Some amps even have metal shields around the rectifier board. Seems that this issue should be approached as diligently as bypass caps (or inline resistors).
Thanks, again!
Edits: 07/23/14
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