Custom Bridge Rectifier on a preamp power supply

Main problem of linear power supply is switching at the max voltage when diodes become polarized in opposite direction. Current drops rapidly to zero and for a moment diode conducts in opposite direction to snap back to zero. What you need is a so called "Soft" diode - a fast diode with slow recovery time like Hexfreds. Diodes that snap back too fast produce ringing that is polluting supply voltage and can couple to any LC circuit. I would not mix diodes. Schottkies have lower forward drop voltage and usually much lower max. reverse voltage.

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)

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'.

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.

^^ 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 :)

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??

Actually I mentioned why that is in my first post on this thread.

There are various types of Schottky(as well as FRED) diodes. ie: Just within those Schottky diodes manufactured with Silicon(as a semiconductor); a variety of barrier heights are available, that result in differing Current to Forward Voltage curves. Some(like ZBD Schottky diodes) are manufactured with Gallium Arsenide. Like the various capacitor and resistor types; each may result in a different presentation, depending on the rest of the circuit. How many different Schottky designs have you tried?

Use a choke input supply instead of cap input and eliminate the huge current peaks that occur in cap input supplies. The input choke very effectively smooths the current draw from the rectifiers. That plus Schottky diodes (amps) or tube diodes (preamps) works best for me.

I also place a 0.022uF + 330R snubber across the +/- between the transformer and rectifier to eliminate any ringing triggered by the switching.