Is it a Zobel or a Snubber
Isnt a snubber actually meant to take care of diode ringing ? And I believe what Carlos's circuit doing is compensating for the high impedance of the power supply. And a Zobel is nothing but an impedance compensation circuit. I guess it doesnt have to be at the output of the amplifier to be called a zobel. So I'd like to think of it as a zobel instead of a snubber. Just my thoughts...which are usually wrong.
😉
What's peculiar is that both share the same configuration - R and C in series - but the values determine their effect.
Running for shelter now....
Isnt a snubber actually meant to take care of diode ringing ? And I believe what Carlos's circuit doing is compensating for the high impedance of the power supply. And a Zobel is nothing but an impedance compensation circuit. I guess it doesnt have to be at the output of the amplifier to be called a zobel. So I'd like to think of it as a zobel instead of a snubber. Just my thoughts...which are usually wrong.
😉What's peculiar is that both share the same configuration - R and C in series - but the values determine their effect.
Running for shelter now....
I agree, and don't really like the 'Snubber'-word in this application.
I think it is, rightly, causing some confusion.
Steen.
Is it the current theory that carlosfm's recommended values apply no matter what the transformer characteristics are (inductance etc.) ?
In other words, if the transformer is a adequate size (VA) or larger is the resulting circuit after the diodes dependent on things after the diodes only and the transformer characteristics (other than some grossly bad transformer) can be ignored as far as the circuit and component values are concerned?
In other words, if the transformer is a adequate size (VA) or larger is the resulting circuit after the diodes dependent on things after the diodes only and the transformer characteristics (other than some grossly bad transformer) can be ignored as far as the circuit and component values are concerned?
My guess is that it would work well with any transformer but the values of the bypass will depend heavily on the value and type of the caps. If you intend using different brand caps you may have to retune by ear.
Can I read in NS papers any recomendation for PS for LM chips ? Is there any concrete recomendation for upgrading sound of this devices by snubber ? If are results so miracle with this, why don't know this guys from NS ?
It is not answer for my questions, to argue with Jeff Rowland. By the way, which PS use this firm ? I mean, that main reason, which lead Mr. Rowland to this solution, is only low price of this chips and better profit 😉 .
Well this circuit is so easy to hardwire I honestly can't see the point in wanting to make a pcb for it.
I did try it out with my LM3886 amp based on Carlos design instead of the LM338 regs, it is actually very good especially the bass punch with a clear mid and top.
Thanks for sharing this mod Carlos, its easy to try and best of all cheap😀
To be honest I'm not sure if I like this snubber or the LM338 best with the LM3886
I did try it out with my LM3886 amp based on Carlos design instead of the LM338 regs, it is actually very good especially the bass punch with a clear mid and top.
Thanks for sharing this mod Carlos, its easy to try and best of all cheap😀
To be honest I'm not sure if I like this snubber or the LM338 best with the LM3886
Back to audio:
I reread the thread but am not clear on where things are regarding the theory of why this works for those who have implemented it. I would like to explore the why and understand what could be measured in order to establish perhaps some ways to predict what the best values would be for particular large caps, transformers etc.
Or perhaps it will come down to the values just work unless the large caps or transformer etc. are grossly different from normal.
So what would be the things to measure to determine "before" or "after" electrically measurably differences?
Note: I am not saying that it needs to be measurable to be real or audible. I am just saying that it would be very useful to uncover what could be measured and then create ways to calculate probable values for particular part parameter variances.
So I believe there has been some speculation so far on possible reasons this works but no concensus. Any proposals on what to measure and test and how?
I reread the thread but am not clear on where things are regarding the theory of why this works for those who have implemented it. I would like to explore the why and understand what could be measured in order to establish perhaps some ways to predict what the best values would be for particular large caps, transformers etc.
Or perhaps it will come down to the values just work unless the large caps or transformer etc. are grossly different from normal.
So what would be the things to measure to determine "before" or "after" electrically measurably differences?
Note: I am not saying that it needs to be measurable to be real or audible. I am just saying that it would be very useful to uncover what could be measured and then create ways to calculate probable values for particular part parameter variances.
So I believe there has been some speculation so far on possible reasons this works but no concensus. Any proposals on what to measure and test and how?
moving_electron said:
Maybe the snubber is discharging the large caps during those moments when it is not necessary for the amp to draw huge currents (high frequencies).
Just wondering... 😕
moving_electron said:
My understanding of the current theory on this is that it probably comes down to the total inductance of the parts used in the PSU before the chip itself. Here's a small pdf I found via google regarding dampening inductance in power supplies:
http://www.designers-guide.com/Design/bypassing.pdf
It appears that there is a formula on page 7, the third one in figure 8, that appears similar to the schematic Carlos posted.
I'm not sure if Carlos can measure the inductance of his PSU and see if his values line up with what's in this PDF or not.
I'll be honest -- I'm taking a shot in the dark, as this stuff is above my current level of knowledge.
motherone said:
And perhaps others that have implemented. A "before" and "after" comparison would be quite interesting.
I thought I one saw speculation that the regulated supply perhaps would appear to an amp as a low inductance supply. Are there any references to this that one knows of. It would be useful to find the common characteristics between the supplies.
I think it is fair to say that low ripple and large reserves in the large capacitors are common to both the regulated and Carlos' bypassed Large Cap supply. Obviously these are not sufficient by themselves or a Large Cap only supply would be fine. So what are the other important characteristics that are common?
Carlosfm's suggested values of 1R and 0.12uF set a filter pole at ~1.3MHz, which places its affects well out of the audio band (a good thing). So it is either elimitaing RF or it is damping PS resonance/oscillation. I agree that it is likely that the best values for the snubber circuit will be dependant on the characteristics of the whole circuit including the trafo etc, and to me it seems that Carlos addressed this by trying various combinations of valuues until he found what worked best for his amp. From my experiences playing with the LMxxxx chips, they are touchy little ******s and like to oscillate when exposed to anything out of the ordinary, so careful management of the PS (or any other circuit system that interfaces to the chips) can make a real difference.
Carlos, I don't know if you will be coming back to this forum/thread, but I for one am interested to know what range of values you tried, and identify the outside boundaries of where you found the snubber began to make a difference. This could help to identify where the source of the problem is that the snubber is correcting.
Metalman
Carlos, I don't know if you will be coming back to this forum/thread, but I for one am interested to know what range of values you tried, and identify the outside boundaries of where you found the snubber began to make a difference. This could help to identify where the source of the problem is that the snubber is correcting.
Metalman
motherone said:
Trying to pull this train back on track... I'd still like to find out if what I posted above has any relevance... Can someone that does have more knowledge in electronics than I do comment on this?
resonance due to xformer winding + caps
It appears that the snubber network is used to 'snub' the resonance that is caused by the transformer's L and the equivalent C in the power supply. Therefore, the proper place should be between the transformer and the diodes. The perceived improvement in sound the way Carlos placed it could be attributed to empirically coming up with an optimal R and C that damped out the total L and C looking back into the power supply.
I guess either placement works well....
It appears that the snubber network is used to 'snub' the resonance that is caused by the transformer's L and the equivalent C in the power supply. Therefore, the proper place should be between the transformer and the diodes. The perceived improvement in sound the way Carlos placed it could be attributed to empirically coming up with an optimal R and C that damped out the total L and C looking back into the power supply.
I guess either placement works well....
Re: resonance due to xformer winding + caps
My understanding was that you also wanted to snub the resonance caused by the Capacitor's inductance. Maybe I'm incorrect, but don't larger capacitors generally have a larger inductance?
If this is the case, wouldn't the formula for this be similar, just including the inductance of both the transformer and the capacitor(s)?
rlim said:
My understanding was that you also wanted to snub the resonance caused by the Capacitor's inductance. Maybe I'm incorrect, but don't larger capacitors generally have a larger inductance?
If this is the case, wouldn't the formula for this be similar, just including the inductance of both the transformer and the capacitor(s)?
Carlos, you mentioned that this PS works well with opamps as well. I am building a power supply for an OPA627/Buf634 at the moment and have been reluctant to use regulators, so this thread was like manna from heaven for me. I have 15-0-15 2a trafo - how do I get the voltage back down to 15v after rectification?
I am using ultra-fast diodes (UF5408). I don't believe they are soft-clipping. Could they introduce extra noise?
I am using ultra-fast diodes (UF5408). I don't believe they are soft-clipping. Could they introduce extra noise?
I think Carlos left DIYaudio.com after the recent "clash" in this thread. (the thread has been moderated)
As for your problem: for bringing down the voltage i guess you could use Zener diodes, but regulators vould be the best IMHO.
(keep in mind that the lm18**\38**\47** chips are opamps too..)
as for clipping or ringing as i have learned it, use some bypass caps. one in paralell with each diode. the value of these caps should be around 0.1uf, though this is not critical.
I use polypropylene caps, unipolar. i dont think they come in bi-polar form..
regards
marius
As for your problem: for bringing down the voltage i guess you could use Zener diodes, but regulators vould be the best IMHO.
(keep in mind that the lm18**\38**\47** chips are opamps too..)
as for clipping or ringing as i have learned it, use some bypass caps. one in paralell with each diode. the value of these caps should be around 0.1uf, though this is not critical.
I use polypropylene caps, unipolar. i dont think they come in bi-polar form..
regards
marius
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