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Old 14th January 2004, 02:39 PM   #1
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Default LC Audio story on current woppling?

LC Audio describes "the theory" behind their capacitor connections in their Class A amplifier and they describe something they call "current woppling". Would this be an issue for one of our DIY projects where we connect a number of smaller capacitors in parallel to create the necessary PS capacitance? To explain it in further detail. If my Aleph-X requires four 22,000uf caps in its PS I was under the impression that I could parallel up four 5600uF caps to form each 22,000uF cap. Am I off track here?

Quote:
Our novelty Virtual 4 pole Capacitor bank is one example. In this bank 10 high speed low impedance power electrolytic capacitors are connected together to form 2 big caps for the amplifier rails. None of these caps are connected in parallel, as this would pose problems with current transfer woppling. This is when several low impedance caps are connected directly in parallel, they tend to compete for the power. The first cap gets current first, then the next tries to take some of the charge from the first, and so on. In terms of sound performance, you get a loss of precision in the high frequencies and a cold midrange at larger power outputs - where the woppling is more severe. One alternative is to use only large can capacitors. This to some extent also will solve the two problems described, however almost any large can capacitor will work very slowly, and play with a slow and out-of-beat bass. The V4P setup however solves both problems! Bass is fast and in sync, while precision in mid and high ranges are intact at all levels. Due to the special V4P network, power is charged and discharged to each cap at exactly the same time and rate. At the output of the V4P network no electrolytic caps are present, so here we found a perfect opportunity to place a huge Polyprop (22uF) which this way will be the only capacitor the amplifier can 'see' above 1 kHz.
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Dan
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Old 14th January 2004, 07:06 PM   #2
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I say that's mostly crap. This has been mentioned before,
and after considerable thought, I realized that interactions
(if any) between unmatched parallel caps is of no consequence.
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Old 14th January 2004, 07:42 PM   #3
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Do they mean "current wobbling" ? I have heard of that but not "woppling" which if it is a real word, is so obscure that google only has 1 hit
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Old 14th January 2004, 07:46 PM   #4
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If 'woppling' isn't a real word, it should be
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Old 14th January 2004, 08:11 PM   #5
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If the word "woppling" exist, I would say that LC is getting one here.
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Old 14th January 2004, 09:12 PM   #6
grataku is offline grataku  United States
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Quote:
Originally posted by Nelson Pass
I say that's mostly crap
yep, sounds like a real WALLOP of it.

On a related note, why do I find that my amps stay on for longer after I power them off if I have a couple of nice big blue computer grade caps instead of the same amount of capacity split into dozens of Panasonic FC or other similar caps?
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Old 14th January 2004, 09:31 PM   #7
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Can I have a double Wopple cheese and a can of Black Gate,
please?
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Old 14th January 2004, 09:55 PM   #8
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Default woppling

One entry found for whopper.
Main Entry: whop·per
Pronunciation: 'hwä-p&r, 'wä-
Function: noun
Etymology: 1whop
Date: circa 1785
1 : something unusually large or otherwise extreme of its kind
2 : an extravagant or monstrous lie

Maybe it is the verb for telling a whooper......
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Old 14th January 2004, 10:04 PM   #9
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Quote:
I say that's mostly crap.
I'm sorry Nelson, we didn't invent this phenomena, it was explained at a passive seminar by the norther European representative of Chemicon (Former Sprague) Capacitors factory.

Now it was back in 1991, so i'm sure the word woppling is not the right word he said, but the phenomena is real enough.

If you have say 5 capacitors in parallel, in a dual rail connection, where the rectifier is in one end, and the amplifier is in the other, and we decide the ESR of each capacitor is 10 milliOhms, and the connection resistance between each capacitor is 2 milliOhms.
Do you (Nelson Pass) dispute that the capacitor nearest to the rectifier is charged with the largest current (since it has only 10 mOhm ESR) , and the one furthest away is charged with only about half the current (since it has 20 mOhm as seen from the rectifier). Then when the charging spike is over, the charge rolls forward from the first capacitor to the last and attempts to equalize the charge over the entire bank. So each capacitor ends up having the same voltage. This is what i have (maybe wrong word) called current woppling.
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Old 14th January 2004, 10:11 PM   #10
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Just wanted to add the schematic to our solution discussed. So easier to follow.

Sorry the text is in Dansih language, but the schematic should speak for itself.

The resistors ensure that the charging spike is equally distributed over the entire capacitor bank, and also equally discharged from all 4 capacitors to the amplifier.

I will just emphasize one point, so everyone in here can understand, also Fred: Only the positive side of the power supply is shown here on this schematic. There need also be a corresponding negative side of this power supply circuit to make it work properly.
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