Yes, you can make your own capacitors it's not hard they are to simple. I use to make cap for high voltage use -15kv- using aluminum foil and glass plate worked quite well. As time went by I figured out better ways of making them. One thing I found out by just experimenting is that the alum foil plates needed to be very solidly stuck to the glass plates. assembled "dry" they would his and buzz like you would not believe vibrating to tune of the signal, so I smoothed the aluminum foil on to the plates with oil. Wow what a difference much quieter and much better performance in the circuit. It's as if energy was lost vibrating the alum plate back and forth. So for audio use, wrap / compress them tite.
poobah said:
you mean this? - I don't see audio frequency mentioned
"Other applications in which soakage can degrade performance are those involving fast-settling ac active filters or ac-coupled amplifiers. In Fig 6's circuit, C1 can be a Mylar or tantalum unit because it always has 0V dc on it, but making C2 polypropylene instead of Mylar noticeably improves settling. For example, settling to within -0.2 mV for a 10V step improves from 10 to 1.6 sec with the elimination of Mylar's dielectric absorption."
Mylar may not be the best but you'll have to work at it to find an example of reasonable audio utility where frequency response is affected by da to within orders of magnitude of the 0.1 dB threshold detectable in dbt
Bench's "data" is pretty weak, and I assumed that we were in general talking about dielectrics better than mylar (which leaves out the popular silver-mica acording to Bob's data) - the obviously bad curves from Bench' are electrolytics and Hi-K ceramic
"ac-coupled amplifiers"... right in the text! Interstage coupling caps are blocking DC/coupling AC between amplifiers.
I have no vote regarding the effect at audio frequencies though. When capacitors require seconds, or fractions thereof, to discharge; it is entirely plausible that audio distortion results.
I have no vote regarding the effect at audio frequencies though. When capacitors require seconds, or fractions thereof, to discharge; it is entirely plausible that audio distortion results.
I would like to see Bench's set up for measurements... schematic with part numbers. A little strange in that what he labels as "hysterysis" is probably the effects of DA.
You're right though... WEAK data, not compiled in such a way that someone else could duplicate his results (methinks a lot of people do that on purpose).
Commendable in the regard that unlike most speaker cable people; he at least publishes something... other than an opinion.
You're right though... WEAK data, not compiled in such a way that someone else could duplicate his results (methinks a lot of people do that on purpose).
Commendable in the regard that unlike most speaker cable people; he at least publishes something... other than an opinion.
Poobah, I think it's almost beyond discussion that DA, or something to which DA tightly correlates, is audible. For some who post on these websites, nothing is known with enough certainty to say anything meaningful about anything, let alone to allow one to make progress. Personally, I'm fine with guessing down probablistic lines, using information I'm able to glean to inform that guessing. For instance, when an engineer of a military capacitor manufacturer tells me that signal integrity is higher the lower the DA, I take that as a sign that DA, or something to which DA tightly correlates, affects signal integrity. Cyril Bateman has performed a series of stringent tests on capacitors, testing for distortion in different capacitors using different designs and dielectrics. His observations follow observations of those who use only their ears as a guide: capacitors with a lower DC (= lower DA) sound better, hence the heirarchy: electrolytic, mylar, polypropylene, polystyrene, teflon. Also of interest, he found that film/foil varieties measure better than metallized counterparts. One reason I would posit for this result---as another guess, for you unknowing types---is that film/foil types have a layer of air between the dielectric and the metal surface, and we all can reasonably guess the effect this would have on resulting DA etc.
SY said:
I would be inclined to guess down those lines, certainly.
SY said:
No doubt. What we most need is to finger the factor that accounts for lower THD of film/foil types. Could be lower DA. Could also be the non-linear R of metallized dielectrics. I'd be inclined to guess that all these factors, including greater vibration etc, combine into one global effect.
For those interested, here are quotations from Bateman's multi-part capacitor series titled "Capacitor Sound," beginning July 2002 in Electronics World and subsequent issues. Bateman is an electrical engineer, now an editor, I believe, of EW, and formerly was a capacitor design engineer, no slouch when it comes to capacitors. To test capacitor distortions, he designed a rig using a computer soundcard with FFT software using pricey audio-grade (cough) components like Holco resistors (should have used Vishays). Initial measurements obtained using this rig were discarded because he realised, part way through his project, that capacitors he used as critical coupling capacitors in the rig---metallised PETs---introduced distortions that ruined the result (an observation that, itself, could provide the basis for interesting discussions about "measuring"). So he ditched the PETs for MKPs (should have used teflons) etc etc, and here's what he found. I give a random selection of quotations, but before doing so I give his most fundamental finding, which is that .... drum roll .... dielectric absorption is the primary factor producing *easily measurable* capacitor distortion. Say it isn't so. Alas, the golden ears have known this for years without resort to or the need for measurements, but how nice now to have measured results now saying so, especially from a once-capacitor design engineer who had to reverse his long held view ("scientific," no doubt, especially when imposed on others) that capacitors are not much different one from another and that DA has little to do with AC-coupling signal integrity etc. Here are some quotes from Bateman which read almost as from a golden ears' book of experience:
"Many capacitors that distort little when sine wave tested without a DC bias voltage, exhibit much bigger distortions with increasing polarisations [ie, bias voltage]."
"Polar dielectrics [ie, mylar] are lossier and take longer for the dielectric to return to its original uncharged state. Polar dielectrics produce easily measured 'dielectric absorption' effects, especially apparent in thin [read: low voltage] dielectrics."
Polystyrene is "perhaps the best of the easily obtained plastic film dielectrics ... It has an N150 temperature coefficient, a very small tan d and the smallest [next to teflon] dielectric coefficient of all film materials."
"For the best, undistorted sound, dielectric choice is obviously all-important."
"A poor dielectric principally influences the levels of the second and even harmonics produced by the capacitor."
"An internal non-ohmic connection in the capacitor ... introduces significant levels of odd harmonics [watch those connections!], the third having the biggest amplitude."
"I have measured many metallised film capacitors having very large third harmonic levels, frequently as much as +20dB higher than others in the same batch. I have not found this problem when foil electrodes are used with the same dielectric."
"To avoid any possibility of a non-ohmic end connection we could use a solderable, soft metal foil electrode and solder it directly to the lead out wires. This is exactly the time proven assembly used by a large maker of extended foil/Polystyrene capacitors. It produces a near perfect, non-distorting capacitor."
"Self-inductance of [an extended foil rolled] capacitor body is then less than its equivalent length of lead wire. These capacitors have almost no self-inductance apart from the 7nH per cm of the lead wires used to connect them to the circuit."
"The resistance of the metallised electrode combined with aluminum's temperature coefficient of 0.0039 results in a non-linear resistance. This may at least partially explain some of the larger third harmonic distortions [in metallised vs. foil capacitors]."
In measurements of metallised stacked vs. rolled PET capacitors, "the stacked film capacitors usually exhibited an increased third harmonic compared to the wound type."
"Depending on circuit arrangements, many capacitors could produce audible distortions. Perhaps this should not surprise us. Audiophiles have claimed to be able to 'hear' PET capacitors for many years."
I believe that for 0.1uF to 1uF values, metallised PET capacitors should first be distortion tested. Because of their rapid increase in second harmonic with DC bias, they should not be used with significant DC bias, relative to their rated voltage, in high quality audio equipment."
"To ensure the claimed performance of a published audio circuit can be repeated, the designer should declare the make, model and rated voltages of the capacitors. Simply stating ceramic, film etc. is totally unacceptable. These tests illustrate how a capacitor with an acceptable single frequency distortion test can produce significant intermodulation on audio when presented with multiple frequencies."
"Single tone 1kHz amplifier harmonic distortion tests ignore distortions caused by the rising impedance of capacitors at low frequencies. It is now clear that large amplitude bass notes and drum beats in music can result in peculiar intermodulation distortions, in an otherwise apparently good amplifier. For my part, I shall disregard any published audio designs which do not report low frequency intermodulation distortion claimsor low frequency harmonic distortion results, especially if the capacitors used are not properly chosen and [!] adequately defined."
All electrloytic capacitors are ****. (paraphrase)
Bi-polar electrolytics are better than all other electrolytics but are still **** and are easily bested by metallised PET, which are themselves ****. (paraphrase)
"Dielectric behaviour with voltage [ie, DA] depends on the voltage gradient in volts/micron and the characteristics of the dielectric. Its [ie, DA] effects are more readily apparent at low voltages with thin dielectric. The dielectric used in low voltage electrolytics is exceptionally thin. Consequently we find increased effects from dielectric absorption when meauring these types [ditto with thin vs. thicker film film capacitors]."
Electrolytic capacitor distortion increased exponentially the higher the RMS test voltage, including at test [signal] voltages less than 1V. (paraphrase)
_______________________
Bateman gives THD and IM distortion numbers for various capacitors under various test conditions. Those numbers define a range of -150dB to -50dB for the various harmonics concerned. Here are some examples:
Class 2 (ie, noisy) ceramic, zero DC bias = 0.00074% THD, -133dB 2HD, -102dB 3HD.
Class 2 ceramic, 18VDC bias = 0.00205% THD, -95dB 2HD, -99dB 3HD.
Another Class 2 ceramic, 18VDC bias = 0.145% THD, -63dB 2HD, -58dB 3HD.
Class 1 ceramic (C0G), zero DC bias = 0.00006% THD, -128.5dB 2HD, -129dB 3HD.
Class 1 ceramic, 18VDC bias = 0.00009% THD, -122dB 2HD, -129dB 3HD.
Foil polystyrene, 18VDC bias = 0.00005% THD, -129dB 2HD, -131dB 3HD. No visible IM distortion.
Foil polypropylene, 18VDC bias = 0.00005% THD, -128dB 2HD, -131dB 3HD. No visible IM distortion.
Wima FKP2 foil polypropylene, 18VDC bias = 0.00006% THD, -126dB 2HD, -131dB 3HD. No visible IM distortion.
Metallised PET, 18VDC bias = 0.00225% THD, -92dB 2HD, -110dB 3HD. IM distortion clearly visible.
63V polar electrolytic, 30VDC bias = 0.00461%THD, -86dB 2HD, -104dB 3HD. IM distortion clearly visible.
63V bipolar electrolytic, 30VDC bias = 0.00225%THD, -93dB 2HD, -122dB 3HD. IM distortion not visible.
"Many capacitors that distort little when sine wave tested without a DC bias voltage, exhibit much bigger distortions with increasing polarisations [ie, bias voltage]."
"Polar dielectrics [ie, mylar] are lossier and take longer for the dielectric to return to its original uncharged state. Polar dielectrics produce easily measured 'dielectric absorption' effects, especially apparent in thin [read: low voltage] dielectrics."
Polystyrene is "perhaps the best of the easily obtained plastic film dielectrics ... It has an N150 temperature coefficient, a very small tan d and the smallest [next to teflon] dielectric coefficient of all film materials."
"For the best, undistorted sound, dielectric choice is obviously all-important."
"A poor dielectric principally influences the levels of the second and even harmonics produced by the capacitor."
"An internal non-ohmic connection in the capacitor ... introduces significant levels of odd harmonics [watch those connections!], the third having the biggest amplitude."
"I have measured many metallised film capacitors having very large third harmonic levels, frequently as much as +20dB higher than others in the same batch. I have not found this problem when foil electrodes are used with the same dielectric."
"To avoid any possibility of a non-ohmic end connection we could use a solderable, soft metal foil electrode and solder it directly to the lead out wires. This is exactly the time proven assembly used by a large maker of extended foil/Polystyrene capacitors. It produces a near perfect, non-distorting capacitor."
"Self-inductance of [an extended foil rolled] capacitor body is then less than its equivalent length of lead wire. These capacitors have almost no self-inductance apart from the 7nH per cm of the lead wires used to connect them to the circuit."
"The resistance of the metallised electrode combined with aluminum's temperature coefficient of 0.0039 results in a non-linear resistance. This may at least partially explain some of the larger third harmonic distortions [in metallised vs. foil capacitors]."
In measurements of metallised stacked vs. rolled PET capacitors, "the stacked film capacitors usually exhibited an increased third harmonic compared to the wound type."
"Depending on circuit arrangements, many capacitors could produce audible distortions. Perhaps this should not surprise us. Audiophiles have claimed to be able to 'hear' PET capacitors for many years."
I believe that for 0.1uF to 1uF values, metallised PET capacitors should first be distortion tested. Because of their rapid increase in second harmonic with DC bias, they should not be used with significant DC bias, relative to their rated voltage, in high quality audio equipment."
"To ensure the claimed performance of a published audio circuit can be repeated, the designer should declare the make, model and rated voltages of the capacitors. Simply stating ceramic, film etc. is totally unacceptable. These tests illustrate how a capacitor with an acceptable single frequency distortion test can produce significant intermodulation on audio when presented with multiple frequencies."
"Single tone 1kHz amplifier harmonic distortion tests ignore distortions caused by the rising impedance of capacitors at low frequencies. It is now clear that large amplitude bass notes and drum beats in music can result in peculiar intermodulation distortions, in an otherwise apparently good amplifier. For my part, I shall disregard any published audio designs which do not report low frequency intermodulation distortion claimsor low frequency harmonic distortion results, especially if the capacitors used are not properly chosen and [!] adequately defined."
All electrloytic capacitors are ****. (paraphrase)
Bi-polar electrolytics are better than all other electrolytics but are still **** and are easily bested by metallised PET, which are themselves ****. (paraphrase)
"Dielectric behaviour with voltage [ie, DA] depends on the voltage gradient in volts/micron and the characteristics of the dielectric. Its [ie, DA] effects are more readily apparent at low voltages with thin dielectric. The dielectric used in low voltage electrolytics is exceptionally thin. Consequently we find increased effects from dielectric absorption when meauring these types [ditto with thin vs. thicker film film capacitors]."
Electrolytic capacitor distortion increased exponentially the higher the RMS test voltage, including at test [signal] voltages less than 1V. (paraphrase)
_______________________
Bateman gives THD and IM distortion numbers for various capacitors under various test conditions. Those numbers define a range of -150dB to -50dB for the various harmonics concerned. Here are some examples:
Class 2 (ie, noisy) ceramic, zero DC bias = 0.00074% THD, -133dB 2HD, -102dB 3HD.
Class 2 ceramic, 18VDC bias = 0.00205% THD, -95dB 2HD, -99dB 3HD.
Another Class 2 ceramic, 18VDC bias = 0.145% THD, -63dB 2HD, -58dB 3HD.
Class 1 ceramic (C0G), zero DC bias = 0.00006% THD, -128.5dB 2HD, -129dB 3HD.
Class 1 ceramic, 18VDC bias = 0.00009% THD, -122dB 2HD, -129dB 3HD.
Foil polystyrene, 18VDC bias = 0.00005% THD, -129dB 2HD, -131dB 3HD. No visible IM distortion.
Foil polypropylene, 18VDC bias = 0.00005% THD, -128dB 2HD, -131dB 3HD. No visible IM distortion.
Wima FKP2 foil polypropylene, 18VDC bias = 0.00006% THD, -126dB 2HD, -131dB 3HD. No visible IM distortion.
Metallised PET, 18VDC bias = 0.00225% THD, -92dB 2HD, -110dB 3HD. IM distortion clearly visible.
63V polar electrolytic, 30VDC bias = 0.00461%THD, -86dB 2HD, -104dB 3HD. IM distortion clearly visible.
63V bipolar electrolytic, 30VDC bias = 0.00225%THD, -93dB 2HD, -122dB 3HD. IM distortion not visible.
anatech said:Hi SY,
That's easy, stick them in a high gain circuit and give them a "twack" with your finger nail. You might get different notes, and so have a new instrument!
-Chris
I have. The results deeply increased my cynicism regarding "designer" capacitors. The best-performing caps in that test were mass-market Sprague, Panasonic, and WIMA. The worst was a hideously expensive Teflon cap.
BTW, this is the basic flaw in the idea of reducing dielectric constant via a foam or mesh dielectric.
I have been wanting to read Bateman's stuff. Is there acces to it anywhere without spending $200 for the back issues?
I do question whether harmonic distortion alone is a valid test.
Were I to guess, and I should know better than to do it here, (
) I would have to think that some other effect, rather than the sub 100 db levels of THD are causing what is heard.
It is easy enough to make a rough model of DA. Has anyone ever run simulations?
Just for fun... how 'bout cryo caps using frozen JP4?
I do question whether harmonic distortion alone is a valid test.
Were I to guess, and I should know better than to do it here, (
) I would have to think that some other effect, rather than the sub 100 db levels of THD are causing what is heard.It is easy enough to make a rough model of DA. Has anyone ever run simulations?
Just for fun... how 'bout cryo caps using frozen JP4?
serengetiplains said:
Isn't this just more cart-before-the horse thinking? Instead of just making assumptions (unless that's all one is interested in), wouldn't it make more sense to first establish actual audibility and then use that as a means to pin down the cause?
Otherwise, all you have are a bunch of speculations which may or may not be the case.
se
Establishing audibility raises all the ugliest of issues... controlled testing.
Speculation is just that, but it is also the vehicle of discovery is it not?
Suppose for the moment we are barking up the wrong tree by looking for THD... then let's look for a new measurment.
I am the biggest skeptic of all, but for the comments/writings I have heard from guys I truly respect; I think this "capacitor thing" might be real.
Speculation is just that, but it is also the vehicle of discovery is it not?
Suppose for the moment we are barking up the wrong tree by looking for THD... then let's look for a new measurment.
I am the biggest skeptic of all, but for the comments/writings I have heard from guys I truly respect; I think this "capacitor thing" might be real.
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