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-   -   Cree diodes (http://www.diyaudio.com/forums/tubes-valves/85492-cree-diodes.html)

5u4 28th August 2006 02:51 PM

Cree diodes
 
When I built my Loftin-White amp, I originally used the 1200V 5A Cree diodes instead of a tube rectifier. Over time & making other mods, etc., I still notice the sound seems to be slightly harsh. I installed Harris FRED 1200V diodes (that I've had good luck with, in other projects) & the sound is noticably warmer / better sounding. The Cree's drop maybe 5 B+ volts, but this is not likely to account for the difference in sound. I've done this swap twice to make sure it wasn't my imagination or whatever. To me, the Cree's sound more like an ordinary normal recovery diode & the Harris more like a tube. Wondering what other peoples thoughts are?

Tweeker 28th August 2006 02:54 PM

Im curious, could you try connecting the FREDs in series with the Schottkies, putting the Schottkies on the output side?

Tweeker 28th August 2006 03:01 PM

What PIV do the diodes actually see?

The Schottkies may have more reverse current, especially if ratings are pushed.

5u4 28th August 2006 03:02 PM

Suppose I could, could you explain why I would want to do this please.

Tweeker 28th August 2006 03:04 PM

If reverse current at high piv is the issue, it would solve it.

5u4 28th August 2006 03:05 PM

Power xfmr 350-0-350....... B+ 400V.

Tweeker 28th August 2006 03:18 PM

Junction capacitance is also lower with the FRED.

altor 28th August 2006 07:42 PM

Cree shottky diodes - are very specific devices.

I've tried to use them as in audio applications at home also in some SMPS applications an my job, and have seen that only in some places (and not in audio :)) there were better then soft ultrafast diodes like BYD57, BYV26, 29, MUR860, 1620, etc.

mach1 29th August 2006 02:13 AM

5U4,

I had a very similar finding to you - tried Cree schottkys in my 6ER5 6GK5 phono pre and ended up putting the snubbed UF4007s back.

pm

jlsem 29th August 2006 02:23 PM

5u4,

Have you tried a 5U4?

John


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