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In Reply to: RE: cryo-treatment : risky for capacitors posted by unclestu on May 01, 2014 at 17:46:22
How hot is this heat treatment? Like blasting it with a heat shrink gun?
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favorite cables: K Works
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bake in oven at about 200 degrees (you'll have to experiment)Polyethylene caps in particular benefit as polyethylene is the principle material in heat shrink. Many other plastics are also used, though, including teflons which require a higher temperature.
recommend a long slow bake out to allow heat to penetrate slowly to the cap core. Caps which are not round benefit most as IIRC they are wound in circular cross section, and then pressed to achieve final shape. This probably causes some internal deformation.
Interesting that the later Yamamoto amps use a wooden enclosure around their coupling caps and fill them with beeswax. I am wondering if the heat from the beeswax immersion is not partially responsible for a change in sound quality (never tried that one so I can't say for sure)
of course YMMV,
Incidentally, when I had some custom caps made up for my shop ( F-Dyne, unfortunately, has been bought out and they no longer seem to want to make custom caps: they are now Electrocube), the engineer on staff pointed out that my preference for sound seemed to be the cpas which were more tightly wound. They had more top end extension and detail
Edits: 05/02/14
I thought cryogenic treatment was to take the material to a very LOW temperature <-150°C.
Are you talking about fast tracking the warmup process when recommending the slow bake oven?
If you take the body of the component up to those temperatures you risk (at best) shortening the life and potential component failure.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
unclestu referred to two (distinctly) different types of treatment. The notion of heat treatment is to better optimize the mechanical windings within the dielectric, while the notion of cryo treatment is to better optimize the crystal boundaries within the conductor. Additionally, the notion of capacitor burn-in is to better optimize the relationship of the dielectric with the conductive windings/film/foil.
from pure speculation or from actual experience?
How was the temperature of 200°C established? You are getting very close to the moulding temperatures for polymers like polypropylene. Unless you have specifically chosen components rated for use in oil exploration, military or automotive applications, you are stressing the component, depending on how long you expose the component for, and risk altering the specification for which the product was tested to.
Let's ignore electrolytics which have a defined temperature rating based on service life and component tolerance specification - the formula for service hours based on temperature is well known as the electrolyte rapidly degrades with temperature. Subjecting electrolytics to such elevated temperatures is therefore foolish.
The heat deflection temperature of plastic caps varies according to the material and the actual value depends on the method of testing, but is around 85 degrees for polypropylene and similar for polystyrene depending on the barometric pressure for testing. Presumably you are trying to relieve stresses in the material, but the shapes are sufficiently simple that this should not be an issue and so the heat deflection temperature is a reasonable value to use. By taking the temperature up close to the melting temperature which is around 210°C for PP, you really are risking altering the performance of the device by potentially altering physical spacings of electrodes and degradation of materials.
Have you compared measurements before and after treatment? If you claim that your heat treatment does no damage and that all parameters such as self inductance, capacitance, ESR, loss tangent (which define the capacitor performance) are the same, how can you be sure that any sonic change you hear is not just due to wishful thinking?
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
My stoves and ovens are not calibrated in Centigrade but in Fahrenheit: Big difference. Maybe you you ought to ask before jumping to conclusions, After all 100 C = boiling point of water 212 F. I've done it and heard the differences. I need no measurement. Strange thing, using a standard hand held multimeter, I can measure no real differences between Solen caps, Oil filled caps, Teflon caps and such. I can hear differences though.
You need not believe me, and personally I really don't care if you do or not.
I believe you Uncle Stu. Really I do.
Most garden variety audiophile grade electrolytic capacitors are rated for an 85 degree C temp limit. 85 degrees C is a lower temperature than 200 degrees F, as I am sure you know. Some electrolytics can take up to 105 degrees C, and those are specifically marked on the outer casing. I suppose you could heat those latter caps up to 200 degrees F with no immediate negative consequences, but capacitor data sheets show that temperature is inversely related to lifespan. Bottom line: I would not recommend heating an electrolytic, at all, ever. They get hot enough inside the chassis of any amplifier to break them in, with time and patience.
but I thought I had made it clear that I was referring to film caps, not oil filled nor electrolytics.
you would never do such a thing as to heat an electrolytic to 200 degrees F, but I thought some of the posts were ambiguous enough that a newbie might not get that point. Someone else mentioned oil caps. As you say, and as the other guy said, it's probably not a good idea to heat those, too. Especially if it's a vintage one with PCBs inside.
For that matter, I would not even think of cryo-treating an electrolytic or oil cap, either.
Well, in that case, you really ought to present your results to the component manufacturers and tell them they are not getting the best performance possible from their products. After all, if there is a subjective improvement to be had by your heating process, they could easily justify adding a premium for the additional process. Plenty of audiophiles will pay for the peace of mind.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
unclestu,
Thanks for the details.
----
Headphone enthusiast.
favorite cables: K Works
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