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Old 4th June 2011, 06:01 PM   #1
JZatopa is offline JZatopa  United States
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Default Are different sized power supply caps ok?

Is there any problem with using different sized capacitors in a power supply. For example if I wanted to build a CRC power supply could I use one large cap (a 100000uf) and a second smaller one (a 10000uf)? Would that cause any problems? Would it matter which cap is closest to the amp circuit and which one is farther?
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Old 6th June 2011, 07:43 AM   #2
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Yes you can use different sizes and should, there is nothing but an arbitrary reason people use the same size caps except maybe that's what they have or they got a volume discount buying several of the same size... although I don't know what you mean by a CRC supply, that doesn't really tell us what it is besides having a resistor between two capacitors.

Is your design regulated or unregulated, what exactly is it? Generally the larger value capacitor would be farther from the amp circuit and the one closer would be either a boutique audio cap if you believe the hype that they sound different, OR one from a low ESR capacitor product group. Don't put a capacitor that is both small AND non-low ESR family group/type between the resistor and the amp, that would be the worst of all 3 choices, although I would not call 10,000uF small with a 100K uf before it unless your amp is exceeding a few hundred watts output.
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Old 6th June 2011, 02:50 PM   #3
JZatopa is offline JZatopa  United States
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The type of power supply I would be trying this with would be an f5 power supply. I am going to be using a gigawork PS (blasphemy I know) and I thought I might replace or add extra caps right before the amp circuit. I was also looking at some large caps in the swap meet which I would use to build my own PS but I was curious if I could use them with other caps that were smaller so I could get everything to fit in my chassis.
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Old 10th June 2011, 06:03 PM   #4
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you should bypass those big caps with something like 100nf.
probably just my habit but i allso use a 15pf bypass too. (i can't recall when did i pick that habit, it just sortha came and since it can do no harm it remained.)
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Old 11th June 2011, 01:20 AM   #5
JZatopa is offline JZatopa  United States
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What does bypassing a cap with a smaller cap do exactly?
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Old 11th June 2011, 01:27 AM   #6
tinitus is offline tinitus  Europe
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I may be one of the few who never liked them small film caps
and I think it sounds perfect without, so why use them anyway

a super sized supply caps are not my favourites either
I tried real big ones once, and it was like they made the amp slow
but I know, it could have been other things doing it
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Old 11th June 2011, 03:41 AM   #7
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Why bypass?...On the attached graph, picture a lone electron at the far left of the curve..as it makes it journey away from the safety of its large capacitance it is venturing out onto the lone dangerous frontier of stray magnetic fields, & RF fields. The further it goes, it needs to be "reassured"......all the way to its final destination. The curves are wrong I'm sure......but the supply needs a low ESR out beyond 50K Htz.

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Old 11th June 2011, 03:52 AM   #8
JZatopa is offline JZatopa  United States
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So bypass caps lowe esr then? Do they do anything else? I thought parallel caps lower capacitance.
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Old 11th June 2011, 03:59 AM   #9
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Caps are additive in parallel. The idea is to keep ESR down at all frequencies, and the environment is full of "pitfalls" the further away from the initial capacitance.

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Old 11th June 2011, 04:16 AM   #10
JZatopa is offline JZatopa  United States
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So why don't people just use high ESR caps and just bypass them?
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