Dielectric Absorption in Capacitors! Could it be the answer?

[Al Klappenberger]

Bob,

You might be right. I don't know of any way to know for sure. It's possible that dielectric absorption manifests itself in other ways than just the way seen by a cap recharging itself after it's discharged. All I can say is that the small value "phantom" caps in the equivalent circuit have resistor values so high that they would have no effect on the response of a filter. I am not convinced that the equivalent circuit shown is the entire story though.

Al K.

[Deang]

"DFDie=Inherent losses in the dielectric caused by molecular polarization dielectric absorption factors of the particular material."

I don't know where this came from, but it doesn't sound right to me. I've never read anything that indicates DA is related to loss, but rather to distortion.

"DA is part of the capacitor model which represents the tendency of the dielectric to retain a charge. In this sense, the computer model features the primary capacitance in parallel with a smaller capacitance which itself is in series with a resistive component representing the dielectric absorption. In practical terms, low values of DA are desirable since they introduce hysteresis which can compromise the small signal transfer function."

It is related to 'K' though in that the lower the Dielectric Constant the better the DA. Evidently capacitors of like material and construction have similiar DA measurements.

http://www.wima.com/absorption.htm

More than anything else it would be nice to get an explanation from GE on their usage note for the motor runs:

"This capacitor series is designed specifically for motor run applications where the capacitors are used in conjunction with permanent split capacitor type motors. They may be used on either 50 or 60 Hertz systems but should not be used at higher frequencies or in applications where higher frequency harmonics are present. For those types of applications the General Purpose AC Capacitors should be used." http://www.geindustrial.com/cwc/products?pnlid=4&famid=7&catid=29&id=motorRun〈=en_US

I've sent several emails to date with no response. Getting a live person on the phone with a real brain is impossible.

[BEC]

Dean,

Get your answer on the 60 hz question from Klipsch engineering. Most of the caps they used in Heritage crossovers are also rated 60 hz AC.

Bob

[Deang]

I think it makes more sense to allow the manufacturer of the capacitor to explain their own usage notes.

"Most of the caps they used in Heritage crossovers are also rated 60 hz AC."

A good thing too or I'd be out of business.

[BEC]

Dean said: "I think it makes more sense to allow the manufacturer of the capacitor to explain their own usage notes.:)"

I hope you don't get them to talk to you about it. If they find out the caps are good for audio, they will probably paint them yellow and get ten times the price for them.

Bob

[mikebse2a3]

Bob,

You might be right. I don't know of any way to know for sure. It's possible that dielectric absorption manifests itself in other ways than just the way seen by a cap recharging itself after it's discharged. All I can say is that the small value "phantom" caps in the equivalent circuit have resistor values so high that they would have no effect on the response of a filter. I am not convinced that the equivalent circuit shown is the entire story though.

Al K.

First efzauner thanks for posting that paper which was very informing.

Al K. I agree and just thinking off the top of my head, I believe to learn anything new about how the Dielectric Absorption is affecting a circuit that we would be interested in we would need to setup a test for the capacitors under similar circumstances as we would use them.

One test would setup the capacitor say for circuits like AC-Coupling for an Audio Amplifier.

A Second test could look at capacitors as used in a Speaker Crossover circuit.

In the tests used in the above article and others I've read they are basically charging the capacitor with a DC voltage and then shorting the capacitor for a period of time and then releasing the short and watching the voltage climb due to the dielectric releasing its stored energy. This test really doesn't look at how the Capacitor would behave under the circuit conditions we are using them.

For the purpose we use the capacitors in the two test situations I've mentioned above the capacitor is passing a Musical Transient type Signal and due to circuit designs the output from the Capacitor is never shorted but instead sees impedances of say 8ohm for the Crossover Circuit and much higher impedances for the AC Coupling in Amplifier Circuits. I believe the test needs to watch what happens to an Impulse Type Test Signal over Time(ETF Computer program?) with the capacitor in a test circuit setup similar to how it will be used normally say in like the two situations mentioned above. Now the hard part, How would we do this? I've got some thinking to do now!!

One thing seems certain to me and thats if a capacitor has trouble at DC voltages then I believe the situation would only get worse with Transient type AC Signals(Music) at the audible frequencies.

mike[]

[johnyholiday]

Johny'Holiday being an old git box slinger has dealt with "aliasing"

aka

dissonant overtones,ever wonder why it's hard to measure the radius of

a star, or a wagon wheels appears to be spinning backward,look it

up,using capacitors with ESR tolerances out of parameters ,an not

matched even amongst themselves,an or a completely different capacitor

type, having it's own "aliasing" aka dissonant overtones

signature,causes some instantaneous analog undersampling-undersmoothing of data,"aliasing"

=jagged, "anti-aliasing"=smooth, a paradoxicalness or fuzzy logic of sort,me an me an me disagree;causing an agreement

[johnyholiday]

Simple example of what is called a ribbon chart, just data points,

which

moving average would be used for best return aka frequency response, an

no whipsaws aka dissonant tones,because of

it's undersampling-undersmoothing parameters 5-wk=aliasing

,8-wk,10 -wk,13-wk ,15-wk=anti-aliasing, on the chart, EMA=Exponential

Moving

Average, or use them all in a

paradoxical fussy logic, looking for the middle ground, an art an

science,somewhat like building crossover networks

[Al Klappenberger]

Guys,

One point here that may make all this moot is that the dielectric absorption seems to be a function of the dielectric material and not much else. All the capacitors that have been taken seriously use polypropylene as a dielectric materail. Even Bob's GE motor run caps that were designed strictly for 60 Hz aplications use this same material. That says that dielectric absorption must NOT be the reason for any difference people claim to hear between brands of caps.

Al K.

[Erik Mandaville]

Mike:

"Eric and Dean and Others I'm sorry if this is a subject your tired of and I sure don't want to cause any arguing because everyone has a wright to their opinion and should choose to spend their money on whatever seems to be of value to them whether its Speakers, Amplifiers, Wire or Whatever. I just believe their is a reason why I believe Capacitors, Wires and Other Things make a difference in sound and eventually measurements that corelate with how we hear will be found that will show why we have a perception of these differences in sound."

Absolutely no need to apologize in the least, Mike! This IS topic that's been discussed pretty often, but you provided some good food for thought. My 'argument' regarding this (or really any) topic has to do with any single individual deciding for others what is or isn't 'good' performance. That the subject at hand had to do with dielectric absorption of capacitors was for me just coincidental. The on-going problem has to do with the concept of trying to establish a set standard for ideal system behavior and 'best' performance. Because of the human variability in tastes and preferences, a standard in this sense couldn't be more of an impossible thing to achieve. Price, wire type, capacitor type, output device type, etc., has absolutely ZERO to do with what one person happens to value or prefer.

That poly-and-oil motor run capacitors are designed for 50-60 cycle systems and not HF, VHF, or UHF applications has absolutely nothing to do with the fact that IMO they work extremely well in loudspeaker crossovers. Evidently Klipsch felt the same way. However, this doesn't mean that they will be appreciated in that respect by everyone, and that's fine. People should feel free to choose what works well for them. This was the reason why I proposed the idea of making a simple complete network (autoformer instead of variable L-pad) that provided the user with the option of choosing between perhaps three differenct capacitor types in the tweeter branch. The extra work involved to do this would be minimal, and it would allow a person to immediately audition the sounds imparted by 1)motor run oil capacitor; 2) more expensive film and foil capacitor with directional inner and outer foils; and 3) an inexpensive mylar capacitor. I'm not sure that the differences between cap types would be enormous, but it might be significant enough to allow for a personal choice to be made.

In terms of what is perceived as 'better' or 'worse' performance is not capable of universal standardization. I my opinion it is not. However, I absolutely think 'better' and 'worse' are available to all of us individually and personally.

Erik

[Erik Mandaville]

I remember a few years back when someone else with a similar point of view put it this way:

"I love this woman very much, so you should marry her."

[Deang]

"...me an me an me disagree;causing an agreement."

There's something I can relate to. Seriously though, interesting stuff.

"I hope you don't get them to talk to you about it. If they find out the caps are good for audio, they will probably paint them yellow and get ten times the price for them."

Maybe twice as much. However, I've found some cases where the non-audiophile versions of the same type cap cost more. I would save $10 on a set of boards if I went with the Vishay 2uF, I suppose $10 is $10 - but I sure wish they were yellow.

Auricap 2uF (.8" x .9") $9.95 (Percy Audio)
Vishay 2uF (.7 x 1.2") $4.82 (Mouser)

Auricap 20uF (1.7" x 1.7") $44.95 (Percy Audio)
Vishay 20uF (1.5" x 2.3") $54.62 (Mouser)

I quit doing my searches on capacitors and audio and decided I might have better luck if I looked at it from the perspective of motors and power systems.

http://www.ecmweb.com/mag/electric_effects_harmonics_power_2/

I love this women very much, you should find one just like her -- makes more sense I think.

You guys have a great Thanksgiving!

[mikebse2a3]

Guys,

One point here that may make all this moot is that the dielectric absorption seems to be a function of the dielectric material and not much else. All the capacitors that have been taken seriously use polypropylene as a dielectric materail. Even Bob's GE motor run caps that were designed strictly for 60 Hz aplications use this same material. That says that dielectric absorption must NOT be the reason for any difference people claim to hear between brands of caps.

Al K.

Al I agree within FamilyTypes of Dielectric Materials used in Capacitors there may be less difference in performance measurable and audible. I also agree that just because the motor run caps are speced at 60Hz in itself doesn't mean they aren't suitable for use in crossovers. I do wonder though if the effect we are describing as Dielectric Absorption isn't also affected by how the Capacitor is Wound/Layered and the Makeup of the Plate Material and the way the Terminal Leads are attached. I believe Dean and Shawn brought up some of these factors.

I guess to sum up my thinking on this I believe standard test we see used on capacitors doesn't show the information we need to explain what some perceive as audible differences in capacitors. I believe the reason there is a difference in the way capacitors sound will be found in the way the capacitor releases it's (Stored Memory/Dielectric Absortion) of the musical signal over time and to hope to see and understand this would require measurement that display in the Time Domain the release of this stored energy.

Guys I really appreciate the information and ideas shared so far.

mike[]

[Al Klappenberger]

Mike,

I think it's the same for caps as for most stuff in audio, That is: If it measures bad, it's bad. On the other hand, if it measure good, it still MIGHT be bad!

Al K.

[Deang]

From: http://ldsg.snippets.org/appdx-ec.php3

I've spent a lot of time in my career, not in audio, but in extremely critical low noise geophone amplifiers and signal conditioners. For those not familiar with these sorts of applications, the key consideration is that the signal is down in the microvolt range and has to be extracted from a lot (> 1 volt) of environmental and system noise. In these apps, since cost wasn't really a consideration, we used nothing but MIL spec Teflon, polystyrene, and polypropylene caps. In the case of every vendor I approved, I had to tour the factory and sign off on their assembly practices. Having said that, I've since found that a lot of what I learned in that environment translates well to audio capacitor considerations...

...Film and foil is superior to metallized film, if you can tolerate the size. By superior, I mean primarily, lower noise. Capacitor noise is generally caused by flaws in the dielectric or poor terminations. The reason film and foil is "better" than metallized foil is one of metallized film's special "features". You will hear vendors speak of metallized foil as self-clearing. All this means is that if there's a pinhole in the film, a temporary arc will vaporize the metal around the pinhole. This is great for long term viability, but bad for noise since each time this happens, it adds noise. Also, most don't tell you that this only happens when the leakage current through the pinhole is adequate to heat the metallization to the point of vaporization. This is primarily a factor in polypropylene, since of all the popular high-stability dielectrics, it's the softest and therefore most likely to: a) have pinholes as received from the film vendor, and/or develop pinholes during winding. Finally, although the theory is that this only needs to happen once per pinhole, after which the metallization around the hole is blown away, it often doesn't work that way in practice. In the real world, all the metallization around the pinhole won't necessarily be cleared by the first (or second or third or) peak.

Another advantage to film and foil is lower ESR since the bulk resistance of the foil is lower than that of the film metallization. I expect this could play a role in any sort of capacitor-induced distortion, since as ESR decreases, the closer the cap approaches a perfect model. Whether the amounts of distortion potentially resulting from this would be audible or not is open to debate. Noise, on the other hand, is clearly measurable and therefore, presumably, audible as well.

Finally, in any discussion of passive audio components, one consideration that can't be ignored is the dynamic range of the signals involved. This is why only better quality dielectrics are really suitable since their small signal and large signal characteristics track better than, e.g., NP electrolytics or even Mylar®. (This difference can also introduce measurable amounts of distortion.) This is also significant in noise Since each pinhole may not be cleared by the first spike to come along, until it gets cleared, noise will be added to the signal. This becomes significant when you consider the 10-20 dB dynamic range of typical audio program material. In other words, those 100 Watt peaks may not come often enough to clear the pinholes since the average power is closer to 1 Watt. (This is also why non-inductive wirewound resistors are better in crossovers than film or bulk metal types, but more on this below.) This does, however, support the contention that metallized film may sound better after "burn-in". For film and foil, the potential advantages to burning them in become debatable...

..Although significantly heavier, tin foil is generally preferable to aluminum foil, although the degree of improvement is debatable. Presumably, this is due to fact that tin is softer, resulting in less residual stress and reduced susceptibility to microphonics...

...Polyester (Mylar®) capacitors should be avoided for all critical applications! If your budget's tight, try using them in trap or Zobel circuits before putting them in the signal path. With poorer electrical characteristics across the board than polypropylene or polystyrene, Mylar® is the entry level for film capacitor dielectrics. For non-critical systems where cost is a major issue, they're at least better than NP electrolytics....

...Avoid oval caps! They're made by winding them round, then flattening them in a clamp while the epoxy sets. This leaves a lot of residual tension which can lead to value creep and microphonics...

...Everyone buys their raw film from the same suppliers. Any vendor claiming to use, e.g., "premium" polypropylene film is, at best, exaggerating. Note that this applies generally to *virgin* film. You can also buy recycled PP film which is generally used for non-critical applications such as packaging and wrapping, or where only the mechanical properties are important. Although I don't know of any capacitor vendors who exclusively use recycled PP film for capacitors, it would be naive to assume that none do. Certainly, the type and class of capacitors I was discussing (MIL spec, low-noise, high reliability) all use virgin PP film.

"Raw" polypropylene typically comes in pellets, either from a chemical company (usually virgin) or a recycler. Further clouding the issue, pelletized PP may contain a mixture of virgin and recycled material. The pellets are then fabricated into film by a mill, which may, or may not, be related to the raw material supplier. Finally, the mills are the folks who actually supply the film to the capacitor vendors. In the case of metallized films, yet another intermediate vendor is usually involved.

The biggest difference in vendors is QA of the winding operation (for wound vs. stacked foil caps, obviously). Constant light tension is required. This is especially critical with polypropylene since it has such little mechanical strength and stability (i.e. it stretches, tears, develops pinholes, and permanently deforms easily!)

The attachment of the metallization/foil to the leads is critical. This has to be a relatively low temperature operation or the film will be compromised. Poor attachment increases ESR and can introduce noise caused by rectification and/or thermoelectric effects.

Some well-regarded brands do sell exactly the sort of flooby dust that the preceding discussion attempts to debunk. As we all know by now, there's very little correlation between audio quality and marketing hype. I'd never rule out the possibility of a capacitor vendor marketing flooby dust, while still delivering top quality parts. The trap and the fallacy is in thinking that the parts' quality derives from the marketing claims, rather than simply sound engineering and manufacture.

DIY'ers spend ridiculous amounts of money for voodoo caps, when they could buy better caps, in most cases, from a wider variety of vendors if they only knew what to order. "Audiophile" caps are priced around the same as MIL spec caps, yet often have less to back up their claims of superiority.

[mikebse2a3]

Mike,

I think it's the same for caps as for most stuff in audio, That is: If it measures bad, it's bad. On the other hand, if it measure good, it still MIGHT be bad!

Al K.

Yes Al

Kind of reminds me of years ago when Amplifier Designers where all pushing for smaller and smaller IM and THD distortion figures thinking less was better while at the same time not knowing that some where acheiving this at the expense of what later became known as increased TIM distortion.

If it measures bad but sounds good then we aren't measuring all the important things that matter!

OR

If it measures good but sounds bad then we aren't measuring all the important things that matter!

mike[]

[mikebse2a3]

Good Info DeanG

When choosing the capacitors and other audio related componets and equipment I choose to spend my money for mostly based on Quality of Materials, Design and Construction and Price and Listening Observations and pay very little attention to some mystic advertising claims otherwise.

mike

[Deang]

I think that's pretty much what we all do. The marketing hype has toned quite a bit over the last couple of years with capacitors.

So, you do "listening observations" too. Yeah, I sit and watch my wife's facial expressions.

[mikebse2a3]

So, you do "listening observations" too. Yeah, I sit and watch my wife's facial expressions.

I'm lucky to have a girlfriend who loves music and good sound. Several times to test myself when I believe I have made some audible improvement I will just have her sit and listen (She is unaware of what improvements I believe I have made) then I'll ask her what did you notice if any difference. On more than one occasion she has described the same improvement in sound that I perceived. The good thing is she isn't into the equipment for her its all about the music.

mike[]

[Erik Mandaville]

Dean:

"I love this women very much, you should find one just like her -- makes more sense I think."

Blue? Yup!

So, I'll respond in blue: Sure, I understand what you're saying, but I want to submit that It doesn't make more sense. You have restated the same message, only slightly differently. The implication is this particular woman has all the qualities a specific person would look for and want in a wife. Suggesting that OTHERS seek out a life-time companion with the SAME personality traits does not take into consideration the possibility that OTHERS may not have the same values or preferences as the guy giving the advice.

What would make more sense, IMO is something like: "I love this woman very much; I hope you also have the opportunity to find someone about whom you can feel the same."

IOWs, the common element to both is the emotional connection. The variable factor revolves around the probability that, although the end result may be the same ("...and they got married and lived happily ever after), the prerequisites for marriage between one couple and another MUST allow for the fact that not all people will look for the same qualities in a life-long companion.

LOL! A sociologist would have a very rewarding field day with all of this.

Now, here's a complicating factor: So, if we once again return to how the 'individual-differences-in-taste and/or preference-factor' relates to audio in general and crossover caps in particular, the problem is that the majority of listeners may not be equipped with the skills needed to disregard the advertisements of the purveyors and decide for themselves. Rather, they are necessarily obliged to rely on the information provided by the campaign and supporters of the seller. As such, the provider of the commodity must work very hard to win-over the trust and respect of those needed for continued survival.

What I think is a good and positive thing about all of this, is that this struggle for existence has provided excellent replacement crossovers for what IME are among the very best loudspeakers ever produced. That we also have the choice between networks sporting sports-car-yellow film and foils and armored-tank-like motor run oils is absolutely an added bonus. In all cases, the products are built to a very high standard and clearly show pride in workmanship.

I still think it would be helpful for customers to have the opportunity to listen to different types and construction of capacitor and have the subsequent luxury of making a choice based on their OWN preferences. My feeling is still that the design and the value and proper working specs of the components in question are more important than the type of part used. It is not possible to say that motor-run oils (thought highly enough about by Mr. Klipsch to use them) are inherently better or worse than film and foil types of the same value. The ONLY person who can decide that is the listener. Some listeners would rather that the decision be made by someone they may (want) to look to as an authority on the subject, but that is something we'll leave for another day.

Erik