Thanks for posting.
-
A bypass-capacitor dialogue peels back the layers
An externally hosted image should be here but it was not working when we last tested it.
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Looking at the graphs above reminds me of another point from his book: Why place a small (0.1uF or similar) across an electrolytic when there is no signal voltage across it anyway? It serves no purpose (paraphrased). Note: here he is talking about audio coupling.
He stresses in a number of places in the book that you have to use an oversize electrolytic value to keep low frequency distortion under control, and he references Cyril Bateman and also shows an AP plot he generated to prove the point. I guess one could argue for the 0.1uF parallel cap on the grounds that the self inductance of the electrolytic rises quite quickly at higher frequencies - just where you want the main cap to continue to behave well.
For the record, I will continue to place a small HF cap in paralllel with my electrolytics. If you are designing high volume consumer products, which he does (e.g. Arcam), then I know from my experiences here in Japan that every penny is big deal.
He stresses in a number of places in the book that you have to use an oversize electrolytic value to keep low frequency distortion under control, and he references Cyril Bateman and also shows an AP plot he generated to prove the point. I guess one could argue for the 0.1uF parallel cap on the grounds that the self inductance of the electrolytic rises quite quickly at higher frequencies - just where you want the main cap to continue to behave well.
For the record, I will continue to place a small HF cap in paralllel with my electrolytics. If you are designing high volume consumer products, which he does (e.g. Arcam), then I know from my experiences here in Japan that every penny is big deal.
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I agree, but am somewhere in the middle. For reliability , derate. For specific applications (Cdom , input , power supply) research the product to match the worst case electrical requirements of the specific circuit.
I am not "anti- blackgate", but I fail to see the advantages of "dirty electrolyte"
(carbon) besides the subjective voodoo associated with the product.
PS , I do know the carbon forms "hairs" in the electrolyte making the cap act more like a cap/resistor hybrid. I suppose one could just put a resistor in parallel with a"real" cap to achieve the same thing ???
OS
---The electrolytic capacitors have the dielectric maintained based on the DC voltage across them.---
What says one of the best makers of electrolytics, chapter "general technical data / shelf life":
http://www.alliedinter.com/images/stories/allied/sicsafco/sic_safco___catalogue_2009.pdf
Using Cyril Bateman's instrument (the white one in the picture below), I've been measuring Tan-Delta's of thousands of electrolytics, some results can be seen on the following thread of a french forum
Des condensateurs chimiques
Conclusion : most electrolytics have reliable performances even when more than 20 years old.
What says one of the best makers of electrolytics, chapter "general technical data / shelf life":
http://www.alliedinter.com/images/stories/allied/sicsafco/sic_safco___catalogue_2009.pdf
Using Cyril Bateman's instrument (the white one in the picture below), I've been measuring Tan-Delta's of thousands of electrolytics, some results can be seen on the following thread of a french forum
Des condensateurs chimiques
Conclusion : most electrolytics have reliable performances even when more than 20 years old.
An externally hosted image should be here but it was not working when we last tested it.
presumably some of that period has been on the shelf with a voltage of <<10% of it's rating applied to it.
Hi,
Shown capacitors were all "new", well, I mean never used, age being about 25 years. They were tested without having any DC applied before. Most had a tan-delta about 0.007.
A few of them (CEF) were faulty with an imporant leakage, one with an Rdc = 15 Ohm. They became quite well restored with DC applied for some time but had never a tan-delta as good as the beloved SIC-SAFCOs.
Note that my conclusions came from all the caps which came to my hand, new or old, used of not. The best tan-delta's I found among electrolytics were of non-polarised type. Reading Cyril Bateman's writings will confirm their high quality.
Shown capacitors were all "new", well, I mean never used, age being about 25 years. They were tested without having any DC applied before. Most had a tan-delta about 0.007.
A few of them (CEF) were faulty with an imporant leakage, one with an Rdc = 15 Ohm. They became quite well restored with DC applied for some time but had never a tan-delta as good as the beloved SIC-SAFCOs.
Note that my conclusions came from all the caps which came to my hand, new or old, used of not. The best tan-delta's I found among electrolytics were of non-polarised type. Reading Cyril Bateman's writings will confirm their high quality.
Hi guys, take a look at the article below... I think this can be the origin of one of the myths...
">Rich Nelson wrote:
>>
>> This is absolutely WRONG. An electrolytic cap works because the the
>> voltage applied across the electrolyte forms the dielectric film.
>> Using a cap much below its rated voltage will not maintain the
>> dielectric, and the value of the cap will decrease over time. And the
>> puncture voltage of the dielectric will also decrease - making the cap
>> more likely to fail!
>
>This is absolutely WRONG. It used to be true, but operating modern
>electrolytics at below rated voltages will not decrease the value of the
>capacitor over time.
>
>To quote, from an article in Radio-Electronics for February
>1970, by Richard R. Marsh of Cornell-Dubilier Electronics:
{Text deleted.}
This exact same thing was said by them in 1952 and they were lying then
too... or perhaps "stretching" the truth might be the polite way of saying
it.
The effect is slow, but it does exist - and basically there is nothing that
can be done about it. It occurs because of the basic chemistry of an
electrolytic capacitor in the formation of an anodic oxide film.
The negative electrode of an electrolytic capacitor is the electrolyte -
which is NOT dry. It must remain moist for the capacitor to operate.
Without the polarizing voltage on the capacitor, the electrolyte will
slowly hydrolyze the aluminum oxide film on the positive terminal or anode.
It will do so until the voltage rating of the capacitor eventually reaches
the potential at which the capacitor operates. The process is slow, but
measurable. Various hydroscopic materials such as sugars, glycols, and
inorganic salts are added to the electrolyte paste in the so-called "dry"
electrolytics to maintain the moisture content. As long as a polarizing
voltage is applied, the anodic oxidation reaction maintains the oxide film.
Even in new capacitors that have been stored for several months, when a
voltage is first applied the leakage current through the capacitor is much
higher than normal. This quickly diminishes as the oxide film reforms.
When you take away the electrolyte, the film does not hydrolyze. But
likewise it can no longer repair itself. Completely dry electrolytic
capacitors have been made, where the anode foil is removed from the
electrolyte bath after the oxide film is formed. The oxide layer is then
sputtered with aluminum to produce the other electrode. However, in the
remainder of the manufacturing process, usually during the rolling, the
oxide film is damaged and the capacitor fails prematurely. Such capacitors
have never been marketed successfully.
There is usually no problem when using a capacitor originally rated for a
higher voltage in a low voltage circuit. However, you do pay a penalty
both in price and in internal resistance when you do this. The effect on
price versus voltage is high, but the added internal impedance of high
voltage electrolytics is generally not a problem except at high frequencies
where the internal inductance of the electrolytic capacitor is already
making the impedance increase.
For those that want to learn more about the chemistry of electrolytic
capacitors, I suggest the book below. I will warn the readers that this is
a book written more for metallurgists and material scientists than for
electrical engineers (much less those who do electronics as a hobby).
By the way, the theory predicts that an electrolytic capacitor, once formed
at a particular voltage, will increase in value as its anodic film
hydrolyzes. For bypass applications this is fine, but this effect is
partially why electrolytic capacitors are never used in critical frequency
determining or timing applications. In practice, the change in capacitance
is not easy to predict since only the most reactive portions of the oxide
film degrade. What many people attribute to loss of capacitance is really
a large increase in internal impedance.
Dr. Barry L. Ornitz WA4VZQ ornitz@dpnet.net"
">Rich Nelson wrote:
>>
>> This is absolutely WRONG. An electrolytic cap works because the the
>> voltage applied across the electrolyte forms the dielectric film.
>> Using a cap much below its rated voltage will not maintain the
>> dielectric, and the value of the cap will decrease over time. And the
>> puncture voltage of the dielectric will also decrease - making the cap
>> more likely to fail!
>
>This is absolutely WRONG. It used to be true, but operating modern
>electrolytics at below rated voltages will not decrease the value of the
>capacitor over time.
>
>To quote, from an article in Radio-Electronics for February
>1970, by Richard R. Marsh of Cornell-Dubilier Electronics:
{Text deleted.}
This exact same thing was said by them in 1952 and they were lying then
too... or perhaps "stretching" the truth might be the polite way of saying
it.
The effect is slow, but it does exist - and basically there is nothing that
can be done about it. It occurs because of the basic chemistry of an
electrolytic capacitor in the formation of an anodic oxide film.
The negative electrode of an electrolytic capacitor is the electrolyte -
which is NOT dry. It must remain moist for the capacitor to operate.
Without the polarizing voltage on the capacitor, the electrolyte will
slowly hydrolyze the aluminum oxide film on the positive terminal or anode.
It will do so until the voltage rating of the capacitor eventually reaches
the potential at which the capacitor operates. The process is slow, but
measurable. Various hydroscopic materials such as sugars, glycols, and
inorganic salts are added to the electrolyte paste in the so-called "dry"
electrolytics to maintain the moisture content. As long as a polarizing
voltage is applied, the anodic oxidation reaction maintains the oxide film.
Even in new capacitors that have been stored for several months, when a
voltage is first applied the leakage current through the capacitor is much
higher than normal. This quickly diminishes as the oxide film reforms.
When you take away the electrolyte, the film does not hydrolyze. But
likewise it can no longer repair itself. Completely dry electrolytic
capacitors have been made, where the anode foil is removed from the
electrolyte bath after the oxide film is formed. The oxide layer is then
sputtered with aluminum to produce the other electrode. However, in the
remainder of the manufacturing process, usually during the rolling, the
oxide film is damaged and the capacitor fails prematurely. Such capacitors
have never been marketed successfully.
There is usually no problem when using a capacitor originally rated for a
higher voltage in a low voltage circuit. However, you do pay a penalty
both in price and in internal resistance when you do this. The effect on
price versus voltage is high, but the added internal impedance of high
voltage electrolytics is generally not a problem except at high frequencies
where the internal inductance of the electrolytic capacitor is already
making the impedance increase.
For those that want to learn more about the chemistry of electrolytic
capacitors, I suggest the book below. I will warn the readers that this is
a book written more for metallurgists and material scientists than for
electrical engineers (much less those who do electronics as a hobby).
By the way, the theory predicts that an electrolytic capacitor, once formed
at a particular voltage, will increase in value as its anodic film
hydrolyzes. For bypass applications this is fine, but this effect is
partially why electrolytic capacitors are never used in critical frequency
determining or timing applications. In practice, the change in capacitance
is not easy to predict since only the most reactive portions of the oxide
film degrade. What many people attribute to loss of capacitance is really
a large increase in internal impedance.
Dr. Barry L. Ornitz WA4VZQ ornitz@dpnet.net"
Certainly the gist is correct, but you still have to be careful with generalizations. I wouldn't use 250V cap in a 15V circuit, but a 63V cap is no problem at all. As mentioned in another post, the worst performing and shortest lived electrolytics I've seen are the very low voltage ones like 6.3V. I wouldn't use one of those in any circuit, and a 25V or 35V cap will work fine and perform better even in a 2V circuit. Then there's the issue of chemistry and construction. Electrolytic caps are definitely not created equal and only history and a collection of test results can be trusted. Thus, when a lot of people report good results over a decent period of time with, say, Panasonic FC series caps, I'd tend to order those, over some lesser known brand.
Conrad Hoffman...beautifull name!...if i had a name that way i would be a sucessfull
man in my country.... sounds great!
There are other strange stories you should explore....that burn in time... strange thing people say that happens.... i could listen people (serious people) saying that have listen music early morning and was "this" way... and when returned (left the amplifier on), the sound was "that" way... different.
I have heard people that said to me an amplifier sound different when is in the floor (rigid) or inside a bookshelf (flexible).
Some folks buy Teflon capacitors...they may think (kidding of course) the eletrons face a slippery, a place to drift or something alike
Others buy golden special capacitors.
Some people say that Panasonic are better....others Elco.... and say the factory is European and high quality company...they are made in Brazil...and go to Europe...and believe it or not..we import our own Gods..some strange arrangements that seems happens here (not sure.... Mitchel said to us.... but the guy is serious)
Silver Mica because can face variable voltage without change characteristics.... not good ceramic, that variates (seems crazy to me)
You have room to study that deeply..and will be a service to this forum and to the audio communitty, to give an end to these Myths... seems big magic to me.
Capacitors have capacitive reactance, some inductance, some resistance... they can face some ammount of voltage without become defective... they have exotic dieletric material, size may be different..how they look...maybe this 10 percent or something alike because makes sense when we think about the chemistry involved...but all other things...better sound...seems big magic to me.
Go ahead please..... my friends wants to build my amplifier and they are asking me what special parts to use..... i am in trouble to tell them to use what they find in the capacitance, size and insulating voltage and not to bother about other "features"....but.... there are a psychological effect...their belief..something alike religion... things not proved and people believe..even against science (woman that had no man and had children) populates their brain... they think special parts creates special sound..some of them believe expensive parts may be better... there's some room to "big magical mistery parts" here.
People say that change that blue capacitor by a green one and sound changed...i think this is all illusion..but the say changed...you ask them to install a relay and to switch one and other and they say they do not need that...that they are sure...and ask you why to spend time doing that when they are sure?.. they do not compare.... and are sure.... can you believe that?
The reality is that their belief "makes" them perceive something different... and we cannot mess with that...... if they use standard parts..they will always thinking they are loosing something..that they are not having the maximum performance.
I said to some of them they are crazy in their minds.... they said I AM the crazy..that i could not listen...that i have not the skills.... my speakers are not good, and because of that i could not listen ants conversations or the grass sound..my ears are damaged... and so on.
Ask me if these guys are stupid?....No!...they are not... some of them have high level of intelligence.... this is the most strange thing.
I am sorry..but one day i will use your name.... this will sell billions in my place.
"Conrad Hoffman Enterprises..the Dx amplifier factory!"...you may think i am kidding..but i am not...here, one the most rich families are "Manesman"...some names are a guarantee....i wich i had a name alike yours...sound good..it is music!
regards,
Carlos
man in my country.... sounds great!
There are other strange stories you should explore....that burn in time... strange thing people say that happens.... i could listen people (serious people) saying that have listen music early morning and was "this" way... and when returned (left the amplifier on), the sound was "that" way... different.
I have heard people that said to me an amplifier sound different when is in the floor (rigid) or inside a bookshelf (flexible).
Some folks buy Teflon capacitors...they may think (kidding of course) the eletrons face a slippery, a place to drift or something alike
Others buy golden special capacitors.
Some people say that Panasonic are better....others Elco.... and say the factory is European and high quality company...they are made in Brazil...and go to Europe...and believe it or not..we import our own Gods..some strange arrangements that seems happens here (not sure.... Mitchel said to us.... but the guy is serious)
Silver Mica because can face variable voltage without change characteristics.... not good ceramic, that variates (seems crazy to me)
You have room to study that deeply..and will be a service to this forum and to the audio communitty, to give an end to these Myths... seems big magic to me.
Capacitors have capacitive reactance, some inductance, some resistance... they can face some ammount of voltage without become defective... they have exotic dieletric material, size may be different..how they look...maybe this 10 percent or something alike because makes sense when we think about the chemistry involved...but all other things...better sound...seems big magic to me.
Go ahead please..... my friends wants to build my amplifier and they are asking me what special parts to use..... i am in trouble to tell them to use what they find in the capacitance, size and insulating voltage and not to bother about other "features"....but.... there are a psychological effect...their belief..something alike religion... things not proved and people believe..even against science (woman that had no man and had children) populates their brain... they think special parts creates special sound..some of them believe expensive parts may be better... there's some room to "big magical mistery parts" here.
People say that change that blue capacitor by a green one and sound changed...i think this is all illusion..but the say changed...you ask them to install a relay and to switch one and other and they say they do not need that...that they are sure...and ask you why to spend time doing that when they are sure?.. they do not compare.... and are sure.... can you believe that?
The reality is that their belief "makes" them perceive something different... and we cannot mess with that...... if they use standard parts..they will always thinking they are loosing something..that they are not having the maximum performance.
I said to some of them they are crazy in their minds.... they said I AM the crazy..that i could not listen...that i have not the skills.... my speakers are not good, and because of that i could not listen ants conversations or the grass sound..my ears are damaged... and so on.
Ask me if these guys are stupid?....No!...they are not... some of them have high level of intelligence.... this is the most strange thing.
I am sorry..but one day i will use your name.... this will sell billions in my place.
"Conrad Hoffman Enterprises..the Dx amplifier factory!"...you may think i am kidding..but i am not...here, one the most rich families are "Manesman"...some names are a guarantee....i wich i had a name alike yours...sound good..it is music!
regards,
Carlos
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this puts some ideas to my mind but they should better be discussed in yet another thread...
Usually I (as an electrical enginier) try to improve what I think are relevant performance parameters - for instance reduce THD - with the blind faith, that the performances I picked as a measure actually corellate to the percieved sound quality.
It seems extremely logical - no alteration of the signal -> most true perception.
But to wich extent is that really the case.
This is an economical question. If I can get away with much less effort in a certain area, why wasting the effort there instead of spending it, where it really matters to percieved quality. (green capacitors if you will
)
these things are lively discussed but has anyone ever done any serious research on these questions?
Usually I (as an electrical enginier) try to improve what I think are relevant performance parameters - for instance reduce THD - with the blind faith, that the performances I picked as a measure actually corellate to the percieved sound quality.
It seems extremely logical - no alteration of the signal -> most true perception.
But to wich extent is that really the case.
This is an economical question. If I can get away with much less effort in a certain area, why wasting the effort there instead of spending it, where it really matters to percieved quality. (green capacitors if you will
)these things are lively discussed but has anyone ever done any serious research on these questions?
Im also a member there, Ill could ask for permission on that forum to show the paper here if its relevant to the discussion.
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