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In Reply to: Re: Hmmm....... posted by Brian Cheney on July 30, 2002 at 12:39:32:
>"You seem to have an agenda here".Yes I do, I am tring to understand your publicized methodology concerning passives tol. specs.
>"You say close parts tolerances are silly".
This is incorrect. I stated that 0.0005% tol. in your application is silly. I consider 0.1-0.01% very close tolerance.
>"I can't respond to that".
A little scientific evidence would do nicely. Less that, I guess you are right in this regard.
>"You say all capacitors are hand peeled".
Ah.....no, I did not. I think you left out the "high tech". This does narrow it down to very few caps. However, there is more than one.
>"I can only say they are no commercial capacitors regardless of price with the tolerances TRT achieves by removing film layers by hand while the cap is under measurement".
This is incorrect. There are a couple of companies who hold the tight tolerances for a "price" (none that high). These caps are surely wound and trimmed close, and then a small percentage fall into a very tight tol. via hand tested selection. One of these companies is of course the company who winds for TRT. TRT is Peter M, not some factory.
>"You say the caps won't hold their value. My past 15 years experience trimming capacitors says they do".
I couldn't agree less. A cap that is 0.0005% tol. will drift out of tolerance merely by holding it in hand. If your test equipment does not reveal this, then your equipment is not capable of testing for 0.0005% tol.
After multiple thermal treatments, the cap will become very stable. However, this will produce a less desirable audio product in the form of higher leakage.
>"When we trim caps we start with undervalues and add small polyprops until the meter reads exact desired value".
You are aware that using multiple bypass caps will have more effect via their speed (much lower time constants) than their trimming effect? A 4.7uF cap trimmed with a 0.1uf cap will sound different than a single 4.8uF cap even if both combinations were 0.0005 tol.
I would think that if a value tolerance of 0.0005% was so important then ESR, ESL, and DA/DF matching would be crucial. What is the acceptable tolerance for these characteristics? What kind of test equipment are you using? What are the test controls (ie temperature, barometer, etc......)?
>"I don't know how many times I have to say this".
I apologize. However, this is the first time I have heard your account of your process. If these issues are documented somewhere, I would be happy to spare your valuable time.
Follow Ups:
If you want to tell me who you are we can continue this conversation privately. I don't like your tone and you seem less interested in finding out why I do what I do than defending your own position, which appears to be only you can define what close tolerances are and might be approppriate.Some caps do change value with ambient temperature, and you can also influence their value by squeezing them--a piezoelectric effect. The caps I use are so enormous holding them in my hand has no effect on value.
I have removed capacitors from 15 year old speakers which still have the original tested value marked upon them. They check out on the nose.
I am well aware of the bypass effect of the trim caps. You can stop speaking to me as if I were some amateur.
I note you continue to cloak yourself in anonymity. I am beginning to understand why.
I thought everybody knew who Dr.J was.You can click his name or the letter (D) next to it to get his web site information.
I believe you can even find his full name listed at the bottom of his main page.
Everyone knows who Dr.J is and I would assume Brian knows. If he doesn't, he should remember his name from this point on. Dr.J is the guy who schooled Brian on capacitors. He should be thankful to the good doctor for the free lesson.
Just had a nice conversation with Dr J on the phone. He seems a fine fellow; he's sending me some sample caps. Everything's wonderful again. My apologies to all.
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