Worthwhile CDP tweak-SNUBBERS on diodes - diyAudio
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Old 4th June 2002, 07:47 AM   #1
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Thumbs up Worthwhile CDP tweak-SNUBBERS on diodes

Hi All,
This is a worthwhile but oft forgotten tweak: Bypass your power supply diodes with snubber circuits, which consist of a resistor (100 ohms) in series with a ceramic capacitor (330nF-470nF). Note that each of the four diodes must be bypassed and that the orientation of the snubber is not important.

The overall impact is too lower the noise floor, thuis allowing more detail, greater perception of subtle nuances, and more emotional involvement with the music.

If you would like to set-up an experiment to see teh results for yourself using an oscilloscope, do teh following:
1. Buiild a simple AC-DC four diode rectifier and add a post-rectification smoothing cap.
2. Set the scope to measure AC and measure between the ground leg of the cap and AC input before teh diodes.
3. Note how distorted the displayed waveform (which should be sinusoidal) is
4. Add a snubber across teh first diode. The waveform should imporve a bit
5. Adding the second snubber goves a much better waveform, 95% pure sinewave
6. Add the next snubber distorts teh waveform a bit, while the last snubber gives the cleanest 95% sinusoidal waveform

Happy listening
Ryan
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Old 4th June 2002, 08:13 AM   #2
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A detailed description of quite similar mods can be found here (Pete Goudreau once more ) and the following posts are worth reading.

Ryan, did you use SMT or THT parts ?
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Old 4th June 2002, 09:51 AM   #3
ALW is offline ALW  United Kingdom
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Default Excellent article here

There's an excellent articel here that tells you how to design the snubber properly, for a given PSU.

http://131.109.59.51/images/pdf/Calc...m_Snubbers.pdf

Andy
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Old 4th June 2002, 12:05 PM   #4
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Yes, thanks guys, I used both sources for the tweak. Pete Goudreau is the best! I used normal non-SMT components. I know that Pete used SMT's. Still the benfit is 90-95% there as judged by teh waveform on the scope.
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Old 4th June 2002, 01:06 PM   #5
mlloyd1 is online now mlloyd1  United States
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Good stuff! Whatever happened to Pete anyway? He had a number of GREAT postings.
mlloyd1

Quote:
Originally posted by ftorres
A detailed description of quite similar mods can be found here (Pete Goudreau once more )
...
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Old 5th June 2002, 05:53 AM   #6
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Can i used this tweak for power amp diode bridge? looks fine too me
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Old 9th June 2002, 05:01 PM   #7
jarthel is offline jarthel  Australia
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Quote:
Originally posted by Dr.H
Yes, thanks guys, I used both sources for the tweak. Pete Goudreau is the best! I used normal non-SMT components. I know that Pete used SMT's. Still the benfit is 90-95% there as judged by teh waveform on the scope.
How did you use the R and C formulas in the PDF?

The formula for R is square root of (L/C). the problem here is L is unknown. Maybe there's a way to calculate it. Also C is another unknown but can be calculated. The only problem is the formula uses R.

thanks for the help.

Jayel
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Old 9th June 2002, 06:39 PM   #8
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Will the snubbers bring any improvements to Schotties diodes?
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Old 9th June 2002, 09:48 PM   #9
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An article in Audio Amateur (now AudioXpress) discussed this very topic in great detail. The article was exhaustive, including theory and a decent amount of math, and was intended for power amps. I guess I can dig it up given a few days.

The article started with measuring the most significan resonance which is a function of the magnetics used, the diodes themselves as well as the load (and possibly a bunch of other things).

Now, the first thing they did was to add parallell capacitors to reduce the frequency of the resonance. Only then did they target the resonances themselves using custom snubbers optimized for that particular frequency. So in short, we measure the problem, reduce it and then go after it.

I believe Pete Goudreau's application is most likely optimal in execution (with SMT's, form factor etc.) and for low power devices, but that for power amps, the suggested method mey be even more effective. My guess is that the method may even find use in Pete's application.

Petter
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Old 14th November 2005, 10:30 PM   #10
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Default Interesting thread but dead links

Hello all,

This was an interesting little thread. Unfortunately one of the main links is dead. Does anyone have the .pdf file referred to? Did Petter manage to dig up the Audio Express article?

Regards,
George.
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