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Anyone tried FREDS (fast recovery epitaxial diodes)

3/3/2000 6:44 AM
Anyone tried FREDS (fast recovery epitaxial diodes)
I was just reading an article by Mark Baier of  
Victoria amp fame (Tonequest report) in which he  
claims the fast diodes sound much better than  
silicon diodes .Do any of the Ampagers have any  
experience with these ?
And now, a word from our sponsors:

3/3/2000 3:57 PM
Jim S.

I'd be interested also. The guys at Vacuum Tube Valley claim they make a noticeable improvement for tube hi-fi.  
3/3/2000 5:17 PM
I have been meaning to but have not. I would think that they might reduce or maybe increase the diode current turnon turnoff "spike". Maybe the best would be a syn active rectfier circuit using a zero crossing circuit. If one turns on a device at the zero crossing you get min energy spikes into the circuit. Dimmers are the opposite of this thats why they cause noise.
3/3/2000 6:21 PM
Correct me If I'm wrong on this ... but I believe the current crop of 'soft recovery' Freds address this problem
3/3/2000 7:37 PM

I would like to know a source or a part  
number for suitable ones for my  
blackface super.  
I have always used solid state rectifiers  
as I don't like sag.  
Is there an advantage to using three diodes  
in series on each AC leg.
3/3/2000 9:24 PM
Try they carry some of these. They are the builders of some of the finest tube audio equiptmentcurrently available.. but most importantly they are extremely helpfull to home hackers (hobbyists) and will take the time to help for free! Up to and including designing circuits ( if you ask nicely)
3/3/2000 9:30 PM
Rob W.
Re: be careful!
Yes, these diodes do make for a subtle difference in sound, but honestly I do not feel that they are worth the hassle to put in. Most of us aren't going for HIFI clean in our tube amps, and basically thats about the only situation you would want to use them in.  
I have tried superfast recovery rectifiers in my Fender and I was not happy with the result. In order for me to keep the tone that I was familiar with, I would have had to improve the filtering around these diodes with a hash filter. *too much of a pain* *and not enough room on a standard fender bias board*  
My reccomendation is to leave the rectifiers alone, as long as they are working properly.  
Best of Luck,  
Rob W. :-)

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