"I doubt that a 9 volt bias would be adequate to prevent the failure of the dielectric causing distortion during AC voltage swings of much greater magnitude (if indeed depolarization of the anodic film is occurrfing at all and causing this distortion"
It's a DC bias that is independent of the AC signal. The circuit uses a 2.5 meg resistor between the charging battery and the capacitors. To the AC signal the 2.5 meg is an open for all intents and purposes. The 2.5 meg also gives a very long time constant as far as discharging the capacitor so the DC voltage is stable through the AC voltage swings.
Rob🙂
It's a DC bias that is independent of the AC signal. The circuit uses a 2.5 meg resistor between the charging battery and the capacitors. To the AC signal the 2.5 meg is an open for all intents and purposes. The 2.5 meg also gives a very long time constant as far as discharging the capacitor so the DC voltage is stable through the AC voltage swings.
Rob🙂
9 volt bias
Doesn't matter whether the dc voltage is stable or not; it's irrelevant to the (purported) failure mode , if it exists, or the distortion-causing event, if it exists.
I guess what I'm wondering is, what does the 9 volt bias have to do with whatever mechanism is causing this "crossover" distortion? Biasing the signal above some arbitrary "zero" point doesn't seem to mean much here. AC passing through a dielectric made by imposing a DC voltage doesn't know anything about the DC bias. Anodizing of aluminum can be done with AC as well as DC; during the cathodic (-) biased portion of the signal, the only reaction occuring on the alumin u m surface is hydrogen evolution (or possibly the reductkion of some other species in the electrolyte). AC anodizing usually contnues up to rather high voltages (30 - 60 volts, depending on the electrolyte) so supposing some mechanism is at work at small signal levels (millivolts to volts) that is non-linear wrt the signal seems specious.
John L.
Doesn't matter whether the dc voltage is stable or not; it's irrelevant to the (purported) failure mode , if it exists, or the distortion-causing event, if it exists.
I guess what I'm wondering is, what does the 9 volt bias have to do with whatever mechanism is causing this "crossover" distortion? Biasing the signal above some arbitrary "zero" point doesn't seem to mean much here. AC passing through a dielectric made by imposing a DC voltage doesn't know anything about the DC bias. Anodizing of aluminum can be done with AC as well as DC; during the cathodic (-) biased portion of the signal, the only reaction occuring on the alumin u m surface is hydrogen evolution (or possibly the reductkion of some other species in the electrolyte). AC anodizing usually contnues up to rather high voltages (30 - 60 volts, depending on the electrolyte) so supposing some mechanism is at work at small signal levels (millivolts to volts) that is non-linear wrt the signal seems specious.
John L.
"I guess what I'm wondering is, what does the 9 volt bias have to do with whatever mechanism is causing this "crossover" distortion?"
The purpose of the 9 volts is to stabilze the dielectric. The cap sees both AC and DC voltages. The dielectirc never goes through zero volts becasue of the DC bias. Becasue the AC signal rides on the DC bias it will never have to pass through zero volts. Without the bias the AC signal would have to pass through zero volts on each negative swing of the cycle. The whole idea is to avoid running the AC through the 0 volt crossing point. The distortion mechanism occurs at the 0 volt crossing point.
Rob🙂
The purpose of the 9 volts is to stabilze the dielectric. The cap sees both AC and DC voltages. The dielectirc never goes through zero volts becasue of the DC bias. Becasue the AC signal rides on the DC bias it will never have to pass through zero volts. Without the bias the AC signal would have to pass through zero volts on each negative swing of the cycle. The whole idea is to avoid running the AC through the 0 volt crossing point. The distortion mechanism occurs at the 0 volt crossing point.
Rob🙂
not to be argumentative but...
Well.. I understand the conceptual "theory' here... buutttt...
there are alot of assumptions being used implicitly w/o justification about the electrochemical stability, the conditions in the boundary layer, the properties of the electrolyte and the anodic film, etc.
Not to mention noone seems willing to propose what the mechanism is that causes the purported "zero crossing distortion". As I pointed out above, AC is used routinely to anodize aluminum up to 50 volts or so with no film degradation during the negative half cycle.
Maybe some EE's should read up on electrochemical principals.
Then again, why use electrolytics in the AC signal path anyway?
John L.
(BTW: someone earlier mentioned polarizing the electrolyte. You can't "polarize" an electrolyte, you polarize the electrodes.)
Well.. I understand the conceptual "theory' here... buutttt...
there are alot of assumptions being used implicitly w/o justification about the electrochemical stability, the conditions in the boundary layer, the properties of the electrolyte and the anodic film, etc.
Not to mention noone seems willing to propose what the mechanism is that causes the purported "zero crossing distortion". As I pointed out above, AC is used routinely to anodize aluminum up to 50 volts or so with no film degradation during the negative half cycle.
Maybe some EE's should read up on electrochemical principals.
Then again, why use electrolytics in the AC signal path anyway?
John L.
(BTW: someone earlier mentioned polarizing the electrolyte. You can't "polarize" an electrolyte, you polarize the electrodes.)
"Not to mention noone seems willing to propose what the mechanism is that causes the purported "zero crossing distortion". "
The mechanism is Dielectric Absorbtion. The best bet is to take a look at the linked Walter Jung and Richard Marsh articles that were published in Audio Magazine. If you go the the second article Part 2 it opens with the effects of DA and what capacitor types are more prone to the phemomenon.
Rob🙂
http://waltjung.org/PDFs/Picking_Capacitors_1.pdf
http://waltjung.org/PDFs/Picking_Capacitors_2.pdf
The mechanism is Dielectric Absorbtion. The best bet is to take a look at the linked Walter Jung and Richard Marsh articles that were published in Audio Magazine. If you go the the second article Part 2 it opens with the effects of DA and what capacitor types are more prone to the phemomenon.
Rob🙂
http://waltjung.org/PDFs/Picking_Capacitors_1.pdf
http://waltjung.org/PDFs/Picking_Capacitors_2.pdf
DA, DF, duh...
I remember reading that article way back when, and more recently after reading another capacitor thread. I don't believe it makes much difference in typical applications, nor do I see where application of a bias DC should affect the DA of an electrolytic. Whether or not the bias stabilizes the dielectric is subject to my reservations re: electrochemical kinetics regarding the anodic film on the electrode.
I guess we just disagree on the sonic merits of this theory.
John L.
I remember reading that article way back when, and more recently after reading another capacitor thread. I don't believe it makes much difference in typical applications, nor do I see where application of a bias DC should affect the DA of an electrolytic. Whether or not the bias stabilizes the dielectric is subject to my reservations re: electrochemical kinetics regarding the anodic film on the electrode.
I guess we just disagree on the sonic merits of this theory.
John L.
I don't understand this, do you say that if the inductor is before the cap, you can't hear it. And if it is after you can?
In both cases the current/frequency is the same in both components....so why the difference?
The inductor before, feeds less high frequency to the cap, than having the cap first feeding the inductor. The bandpass maybe the same.
I say that if the BGN is irritable by HF as alleged and has some self resonance, it goes out of the sonic picture if in a bandpass you use L to C than C to L. At least It worked practically in my speaker. They aren't textbook components SY, they don't conform to everything expected apparently.
I'm unclear on how nonideality figures into it. Conservation laws mean that the flow of electrons must obey continuity equations, and there's no component that's so un-ideal that it violates fundamental conservation laws of the universe.
Either that or you're in for a Nobel.😀
Either that or you're in for a Nobel.😀
Salas could you show a schematic?
I'm somewhat puzzled, it reads like you have only the orientation of a LC twopole?
regards
I'm somewhat puzzled, it reads like you have only the orientation of a LC twopole?
regards
salas said:
Then the order doesn't matter. This is AC, and in this Universe, charge is conserved.
I know SY. I tell you what happened. I did not bother doing the rewiring just for fun. I am not taken by the UFOs.
Are you certain? 😀
I think you're the last person I need to tell about the powerful effects of of suggestion and predisposition.
I think you're the last person I need to tell about the powerful effects of of suggestion and predisposition.
SY, that was serendipity. It was there until I reversed it and it was gone. Just that. Go figure... Personally I like hard facts and it actually annoys me not to know the root of some peculiar phenomena, but there are findings too. And if it works its OK in my book. Nobody suggested me to do it.
- Status
- Not open for further replies.