Yes that would be a worthwhile article, I'd publish it if done right.
As it is, I have a short piece in the next issue of Linear Audio about the marked decrease in distortion in a specific cap in the first several hours. Looks like the first measurement of a burn-in type effect. Although the distortion is back up somewhat at the next switch-on, the "burn-in" has partly a lasting effect.
The author does not know yet what the cause is, maybe we find that later.
jan didden
my theory is that since the voltage accross the cap allegedly
causes the distortion ...... the larger the cap value the less
the distortion ( @ any given frequency (and impedance))
so raw capacitance may be able to
swamp out
sutleties of materials used ......
At last one person who thinks about this...
jan didden
You might be informed that I studied caps over a period of years. I gave lectures on them at the local AES, when I was chairperson. People used to joke about me and my cap fixation. You, Jan, appear to want to travel that road. Well, good luck to you, but I solved MY problems with caps by using really good ones where it counts, fairly good ones for bypassing, and avoiding using coupling caps if at all possible. I don't have a problem with cap distortion, Sony does. Please don't think that we have not tried various combinations, including DC biasing, inverse paralleling, (see my 78 paper), bypassing, etc. The best (coupling) capacitor is NO capacitor. Next best is polystyrene or polypropylene. Third best might be PPS. Everyone should know that.
Mid-fi is the phrase invented to denegrate other people's expensive equipment we don't like.
It should be relatively easy to test the audibility of distortion with single or double blind tests by inserting them in a circuit and shunting them out or by A/B testing them with other caps of the same value in a blind test. But then facts are not nearly as much fun as arguing a point without them. And by making actual waveform distortion measurements. The problem with facts is that it brings the entertainment of arguing and holding on to preconceptions to an end. Not having any test data means we can hold on to our common wisdom audiophile prejudices and bash people authoritatively with them indefinitely.
Really? In FET circuits as well? Hmmm, I'm looking at my preamps and they all seem to have coupling caps that are mostly 0.01-0.033uF. And of course, the C0G should work fine for RIAA eq networks and compensation as well. If you're interested in doing a blind evaluation versus some caps of the same value you think (without serious testing) are better, we can arrange that.
Jan, the other approach to keeping the voltage across the cap low is to keep the other circuit impedances high. I'd argue that this is even more effective, since this reduces the signal current.
Jan, there are FETs in this world as well.
Pheonix, it depends on what the caps' positions are in the circuitry. I avoid "audiophile" caps because of microphonics, quality control, and reliability. I frankly don't worry much about lead material. In my last two preamps and in the output stage of my modified crossover, coupling caps were Wima polyprops, nice industrial quality, non-microphonic, and they'll outlive me, even when inside those hot boxes.
Pheonix, it depends on what the caps' positions are in the circuitry. I avoid "audiophile" caps because of microphonics, quality control, and reliability. I frankly don't worry much about lead material. In my last two preamps and in the output stage of my modified crossover, coupling caps were Wima polyprops, nice industrial quality, non-microphonic, and they'll outlive me, even when inside those hot boxes.
Well, everyone, live with 0.1uF or less values for everything, if you wish, but IF I have a coupling cap, it is usually 1uF or more. Having a FIXATION on COG ceramics, (I rarely use them for ANYTHING) and a prejudice against other materials such as polystyrene, Teflon, or polypropylene isn't efficient or productive, from my point of view.
Funny, I don't recall anyone EVER having a fixation, or even a prejudice, against polystyrene, Teflon, or polypropylene in this forum; or even a single negative opinion. What I HAVE seen is a fixation and prejudice against ALL ceramics at ALL locations inside an audio chassis.
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