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Cree shottky in HV .

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Posted on March 27, 2015 at 11:54:56
Wojciech
Audiophile

Posts: 4131
Joined: June 23, 2009
 Has there been anybody's experience that Cree shottky diodes in HV rectifier position sound rather harsh, shrill and sibilant compared to regular cheap SS rectifiers? (or I just elude myself)
TIA, W

 

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RE: Cree shottky in HV . , posted on March 27, 2015 at 19:33:31
Chip647
Audiophile

Posts: 2653
Location: The South
Joined: December 24, 2012
 Haven't noticed any of that. Are you sure your voltages are correct after the mod?

 

RE: Cree shottky in HV . , posted on March 28, 2015 at 06:45:43
Wojciech
Audiophile

Posts: 4131
Joined: June 23, 2009
 Voltages are spot on. I have to listen a little more before I get into tedious process of reversal and screw up the assembly as usually happens.
I only ask here because I vaguely recall one post on Audio Note kits forum stating that everybody is enamored by speced superiority of Cree shottkys but nobody really comment on sound which is rather sharp and unpleasant. It was years ago and I didn't pay attention to the single voice among the crowd of happy campers.
Rgrds, W

 

RE: Cree shottky in HV . , posted on March 28, 2015 at 08:39:35
Wojciech
Audiophile

Posts: 4131
Joined: June 23, 2009
 Here , I found a comment by Neff from one of his postings
..." I experimented with Cree no noise diodes, but as advised by others now use simple UF4007 diodes..."
????
What others? and why they advised against Cree diodes ? Almost all I read on this board is that Cree is next best thing to sliced bread , hmmm

 

RE: Cree shottky in HV . , posted on March 28, 2015 at 13:44:58
Chip647
Audiophile

Posts: 2653
Location: The South
Joined: December 24, 2012
 The diodes are just one piece of the power supply. It almost sounds like you have an ultrasonic oscillation if you are getting annoying sibilance. Sometimes changing parts will make a marginally stable circuit become unstable. Bad sound from diodes comes from the noise they are injecting and radiating. How close are the diodes physically to your signal section? Try using a hash choke.

 

RE: Cree shottky in HV . , posted on March 28, 2015 at 16:25:58
Wojciech
Audiophile

Posts: 4131
Joined: June 23, 2009
 The proximity of PSU to signal circuit is a no issue . But you're right , I have to check for ultrasonic junk. The effect is subtle but rather annoying so I didn't think it might be a sign of instability.
Thanks!!

 

RE: Cree shottky in HV . , posted on March 29, 2015 at 08:47:04
Chip647
Audiophile

Posts: 2653
Location: The South
Joined: December 24, 2012
 You would be surprised. Oscillations at Mhz or Ghz have a range if impacts. If you are hearing something annoying, there will be crap riding on your B+ rail. Cree Schottky diodes don't produce ultrasonic crap from switching noise on their own, this is why they are good.

One thing to look for since the advent of lead free parts are solder joints that look good, but are not. I have run into solder joints that look perfect in every way, that were ultimately bad. Very hard to track down. If your solder joints on your Crees are not perfect, they will transmit junk.

 

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