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HelloQuestion: does anyone here prefer silicon rectifiers and if so why?
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I've had good results with Motorola MUR4100E ultra-fast recovery diodes in a conventional bridge. They're quiet in my amp. I have not used snubbers but there is a 0.1uF 1000v cap across the rectifier output, in parallel with the first smoothing cap in a CLC filter.My amp is a fully balanced (differential and P-P) design, so there are no unbalanced stages anywhere. I guess any power supply noise will be common mode, so maybe that's why there's no audible noise through the speakers. If I had a single ended design, then the noise from the PS might be a problem, I don't know.
Al, hi. If you are going to use these things be sure to listen to the Fairchild Stealth. There are other Fast-Soft Recovery types as well. Most of these come in TO-220 rather than axial packages. If you have to use a solid state diode there are much better options than the typical silicon type. The Stealth and bretheren are light years better.
Ok thanks for the info. I'll look em up
Good reasons for selecting SS rectification exist. Lower cost and better bass are (IMO) pretty obvious reasons.Scads of examples, good and bad, exist for PSUs built around both vacuum and SS diodes. Implementation details govern the outcome.
Eli D.
HiYes I have notice that bass is noticeably tighter when I use a plug in SS rectifier, in truth the whole sound stage is noticeably tightened up. Background noise is increased to a slight high pitched buzz just above the normally very quiet background I have achieved in my amp, not detectable without placing ear next to speaker though. I have added snubbing caps from rect anodes and cathode to the reservoir common point but this has little effect on this buzz. PSU is quasi choke input with only 1.25 uF res cap and 6H choke followed by a second 32 uf cap 1H choke and finally a 200uF cerafine cap. Remember them?
There is a latching relay switch to give manual B+ switch on that is fail safe so that if the mains quits for a minute or two the B+ is disconnected until I trigger the relay again this to allow use of DH rects like 5U4 and of course SS cos we don't want 600 plus volts to appear before the tubes draw current. This is a hazard of choke input!SS kinda goes against the grain though doesn't it but if it suits well.... ;o)
have you tried high voltage (mica) caps across the diodes ?
HiStragley I have just implemented snubbing caps like this and yes it does quieten things way down. I did have snubbers from anodes to ground but that obviously didnt work
Thanks
Al,Scan the Bottlehead Forum archives for RRSF. The technique allows you to "silence" inexpensive UFnnnn SS diodes.
Eli D.
The relatively recent introduction of high PIV Schottky diodes has changed the game some more. Unlike PN junction parts, Schottkys don't exhibit a reverse recovery spike. That makes them as quiet as vacuum diodes.FWIW, I'm partial to UFnnnn parts. They are pretty quiet to begin with and they can be snubbed into "silence". UFnnnn diodes are inexpensive and I'm a CHEAPSKATE. ;~)
Eli D.
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