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Custom Bridge Rectifier on a preamp power supply

I need an advise from any memebers with experiences in custom bridge rectifier. I am thinking about building my own bridge rectifier. Can i mix two different diode ( 1 pair of Fred and 1 pair of Schottky)?? From my expereinces A Fred diode gives me more of a relax sounding( laid back, imaging are much laid back) and a Schottky diode ( dynamic, was more of in your face sounding) too much of forward sounding. To compomise, is it possible mixing two pair of diode together? Any advise are much appreciated!
128x128zipost
rodman99999
6,162 posts
 
You cannot mix diode types, as Mr K mentioned. I've personally had a great deal of success with IXYS HEXFREDs and HEXFRED bridges. ie: (http://www.partsconnexion.com/rectifier_diode_fred.html) & (http://www.partsconnexion.com/rectifier_bridge_hex.html) I've also used CREE SiC Schottkys in some applications. ie: (http://www.partsconnexion.com/rectifier_diode_cree.html)
atmasphere's avatar
atmasphere
11,874 posts
 
The big issue is that rectifiers make noise due to a phenomena called 'swept resonance'. This is caused by how the rectifiers turn off in conjunction with the power transformer inductance.

To prevent this problem the rectifier has to be neutralized. There are several techniques. However once done properly the rectifier will no longer have a 'sound'.
kijanki's avatar
kijanki
4,430 posts
 
Atmasphere, not only power transformer but also inductance of electrolytic caps. There are snubbers, capacitors parallel to diodes etc. but the best is to start with a soft diode. Inductance of big electrolytic caps is in series with the output. People often make mistake by adding non-inductive caps in parallel, creating parallel resonant circuit. So called linear power supply is in reality a primitive switcher and has so many problems that should be already obsolete and replaced by quiet SMPS.
atmasphere's avatar
atmasphere
11,874 posts
 
^^ I was trying to keep my response simple!

I saw a really simple solution that involved the use of a tube rectifier, which due to its linearity does not induce swept inductance issues. It was bypassed with a set of ordinary diodes. So when the diodes cut off, the tube rectifier took up the very brief load, preventing the resonance from getting started... only works if you have the winding for the filament though... and the room :)
zipost's avatar
zipost OP
199 posts
 
Basically i can not mix diode. I am having problems with the schottky diodes, they seems to be in your face ( too forward). Is there a reason for this? Is there a way i can fix this, or it's just the character of Schottky. Please advise??
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