Cree diodes

5u4 · 28th August 2006, 02:51 PM

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

28th August 2006, 02:51 PM	#1
5u4 diyAudio Member Join Date: Nov 2005 Location: N of Tampa	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?

28th August 2006, 02:54 PM	#2
Tweeker diyAudio Member Join Date: Dec 2004 Location: Cincinnati, Ohio	Im curious, could you try connecting the FREDs in series with the Schottkies, putting the Schottkies on the output side? __________________ Be sure your foil hat has a good low impedance ground.

28th August 2006, 03:01 PM	#3
Tweeker diyAudio Member Join Date: Dec 2004 Location: Cincinnati, Ohio	What PIV do the diodes actually see? The Schottkies may have more reverse current, especially if ratings are pushed. __________________ Be sure your foil hat has a good low impedance ground.

28th August 2006, 03:04 PM	#5
Tweeker diyAudio Member Join Date: Dec 2004 Location: Cincinnati, Ohio	If reverse current at high piv is the issue, it would solve it. __________________ Be sure your foil hat has a good low impedance ground.

28th August 2006, 03:18 PM	#7
Tweeker diyAudio Member Join Date: Dec 2004 Location: Cincinnati, Ohio	Junction capacitance is also lower with the FRED. __________________ Be sure your foil hat has a good low impedance ground.


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28th August 2006, 03:02 PM	#4
5u4 diyAudio Member Join Date: Nov 2005 Location: N of Tampa	Suppose I could, could you explain why I would want to do this please.

28th August 2006, 03:05 PM	#6
5u4 diyAudio Member Join Date: Nov 2005 Location: N of Tampa	Power xfmr 350-0-350....... B+ 400V.

28th August 2006, 07:42 PM	#8
altor diyAudio Member Join Date: Oct 2003 Location: Europe-Asia	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. __________________ Regards, Alex

29th August 2006, 02:13 AM	#9
mach1 diyAudio Member Join Date: Sep 2004 Location: Brisvegas	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

29th August 2006, 02:23 PM	#10
jlsem diyAudio Member Join Date: Jun 2003 Location: Dallas,TX	5u4, Have you tried a 5U4? John __________________ When an LP gets scratched it still makes sense; when CDs crack up they go completely senile and gibber incontinently. - Hugo Williams

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