http://www.diyaudio.com/forums/attachment.php?s=&postid=534018&stamp=1103139431
Above we see Carlosfm's power supply for Gainclones.
We see also that roibm have implemented these snubbers and they can be seen here.
Can anybody give a trustworthy explanation how they work and what they should eliminate?
Looking at the schematic above Carlos have a 100 nF in parallell of 1R+ 100nF. Does this make any sense? What would the 1 ohms resistor do? Why not 10 ohms or 2.2 ohms?
Above we see Carlosfm's power supply for Gainclones.
We see also that roibm have implemented these snubbers and they can be seen here.
Can anybody give a trustworthy explanation how they work and what they should eliminate?
Looking at the schematic above Carlos have a 100 nF in parallell of 1R+ 100nF. Does this make any sense? What would the 1 ohms resistor do? Why not 10 ohms or 2.2 ohms?
There is a thread somewhere here that shows spice simulations of diode/transformer ringing. I believe RC filter damps the ringing and the C only filter changes the frequency. The conclusion was to use both.
I think to make an ideal filter you probably need to optimize for a specific diode/transformer combination. But even non-optimized snubbers should generally help.
I think to make an ideal filter you probably need to optimize for a specific diode/transformer combination. But even non-optimized snubbers should generally help.
Konnichiwa,
Yes, someone can.
Yes, to a degree. I'd probably like to see larger capaictor values.
One should think it was obvious. Just draw out the full RLC equivalence ciruitry for the whole lot oc capacitors and analyse it....
1 Ohm is probably still a little high but a convenient value to get off the shelf.
Sayonara
peranders said:
Yes, someone can.
peranders said:
Yes, to a degree. I'd probably like to see larger capaictor values.
peranders said:
One should think it was obvious. Just draw out the full RLC equivalence ciruitry for the whole lot oc capacitors and analyse it....
peranders said:
1 Ohm is probably still a little high but a convenient value to get off the shelf.
Sayonara
peranders said:
you have a resonant circuit formed by the transformer secondary, the interwinding capacitance and the capacitance of the diodes. you can ex ante determine the ringing frequency from all the above, providing you have a calculator which takes square roots!
The RC network snubs the ringing.
Carlos' values are not optimal and I don't know what methodology he used to determine them. Too large a capacitor, too low a resistance wastes energy and can actually inject RF into the system. Purportedly, the effect of a badly designed snubber is audible to even those not gifted with golden ears -- (if you have ever made your own pulse-width modulated motor controller you know what I am talking about.)
The equations can be found here, the article is a follow-up to one Jim Hagerman wrote for Audio Amateur:
http://www.hagtech.com/pdf/snubber.pdf
or the more complete version, with more greek symbols and plenty of graphs:
http://www.cornell-dubilier.com/tech/design.pdf
Cornell-Dubilier has a simplified version also.. www.cde.com/catalogs/5.029-5.031.pdf
You might want to read this one too - www.calex.com/pdf/3power_impedance.pdf
You might want to read this one too - www.calex.com/pdf/3power_impedance.pdf
peranders said:
I have recently tried 100uF + 1R in parallel with 10,000uF and it works as advertised by Carlos on my minimialistic IGC. Thanks Carlos for sharing this information. I used a 1 watt 1R and using 17-0-17 VDC it only gets slightly warm. I wonder if 1 watt rating is even necessary?
Simple mod highly recommended.
As usual with audio, YMMV.
Thorsten, did you read the whole question and also looked at Carlos schematic?Kuei Yang Wang said:
I think you all guys have missed my question. My question was the explanation of one 100 nF in parallel with 1 ohms + 100 nF. It seems that noone here can explain that, not even Thorsten. I'll guess this will be in the placebo department for now.
Note that I fully aware of that sometimes it needed to limit the minimum impedance but you aren't doing that in this case.
Per,
Absolutely.
Absolutely, I was refering to that in my reply. So please do as I suggested and the answer will be BLINDINGLY OBVIOUS to you.
On the contrary.
1) I understand fully what is going on with these bypasses
2) I am actually aware that these bypass/snubber combo's are not ideal, because I understand how they work
3) As suggested by CarlosFM I am certain the combination works better in an electrical way, than either no bypass or or using snubber or bypass only. This may very well reflect in the sound of the amplifier.
4) I can mathematically derive a more optimum combination if the ESL's and ESR's of the capacitors are known.
5) I choose not to explain this to you as the issues and derivation as well as calculation is basic electrics and I think it would be a good excercise for you to work it out yourself. Especially as you are "Mr. I'll shjow the world how to make Chip Amplifiers", with that kind of attitude I'd actually expect yo to know these things and to account for them in your designs....
For fun, assume 1uH ESL for the 10,000uF capacitor and 9nH for the 100nF.
Suit yourself. I find it sad how often self styled experts miss even fairly obvious things and then, instead of attempting to understand for themselves they insist others explain to them and plainly refuse to even consider applying a modicum of analysis to what they "don't like".
Sayonara
peranders said:
Absolutely.
peranders said:
Absolutely, I was refering to that in my reply. So please do as I suggested and the answer will be BLINDINGLY OBVIOUS to you.
peranders said:
On the contrary.
1) I understand fully what is going on with these bypasses
2) I am actually aware that these bypass/snubber combo's are not ideal, because I understand how they work
3) As suggested by CarlosFM I am certain the combination works better in an electrical way, than either no bypass or or using snubber or bypass only. This may very well reflect in the sound of the amplifier.
4) I can mathematically derive a more optimum combination if the ESL's and ESR's of the capacitors are known.
5) I choose not to explain this to you as the issues and derivation as well as calculation is basic electrics and I think it would be a good excercise for you to work it out yourself. Especially as you are "Mr. I'll shjow the world how to make Chip Amplifiers", with that kind of attitude I'd actually expect yo to know these things and to account for them in your designs....
For fun, assume 1uH ESL for the 10,000uF capacitor and 9nH for the 100nF.
peranders said:
Suit yourself. I find it sad how often self styled experts miss even fairly obvious things and then, instead of attempting to understand for themselves they insist others explain to them and plainly refuse to even consider applying a modicum of analysis to what they "don't like".
Sayonara
Occam, a memebr of another forum kindly gave me these two links. I found them very informative and worthwhile reading.
www.calex.com/pdf/3power_impedance.pdf
www.designers-guide.com/Design/bypassing.pdf
www.calex.com/pdf/3power_impedance.pdf
www.designers-guide.com/Design/bypassing.pdf
I just notice my first link has all ready appeared in this thread. My apologies percy. 
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