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Old 28th August 2006, 02:51 PM   #1
5u4 is offline 5u4  United States
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Default 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?
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Old 28th August 2006, 02:54 PM   #2
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Im curious, could you try connecting the FREDs in series with the Schottkies, putting the Schottkies on the output side?
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Old 28th August 2006, 03:01 PM   #3
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What PIV do the diodes actually see?

The Schottkies may have more reverse current, especially if ratings are pushed.
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Old 28th August 2006, 03:02 PM   #4
5u4 is offline 5u4  United States
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Suppose I could, could you explain why I would want to do this please.
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Old 28th August 2006, 03:04 PM   #5
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If reverse current at high piv is the issue, it would solve it.
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Old 28th August 2006, 03:05 PM   #6
5u4 is offline 5u4  United States
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Power xfmr 350-0-350....... B+ 400V.
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Old 28th August 2006, 03:18 PM   #7
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Junction capacitance is also lower with the FRED.
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Old 28th August 2006, 07:42 PM   #8
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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.
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Old 29th August 2006, 02:13 AM   #9
mach1 is offline mach1  Australia
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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
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Old 29th August 2006, 02:23 PM   #10
jlsem is offline jlsem  United States
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5u4,

Have you tried a 5U4?

John
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