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Old 26th August 2009, 02:49 PM   #11
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Great replies, thanks so far...

I understand that increasing capacitance = increased inrush etc etc.

going back to infinia's reply if I may:
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Akis brings up a really important part about parallel wiring, just using PWB ground planes is NOT a good idea
OK, enlighten me: why is using planes NOT a good idea?

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In engineering, properly changing one thing w/o considering all the angles, usually just results in other problems not improvement.
Ain't that the truth!

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Old 26th August 2009, 08:18 PM   #12
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Quote:
Originally Posted by panson_hk View Post
PCB cost is nothing compared to an large, expensive capacitor. To use multiple smaller cap in parallel, we need to make sure them operating in a balance manner.
I was saying about pcb size, not price. Will the pcb fit in the case?
If he has big case, he can use big tall caps with no problem, but if the case is small...
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Old 26th August 2009, 09:10 PM   #13
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OK. Case size is not the main issue.
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Old 26th August 2009, 09:15 PM   #14
osscar is offline osscar  Latvia
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IMHO: main issue - budget i will go for big ones.
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Old 27th August 2009, 01:21 AM   #15
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Quote:
Originally Posted by petrusevski View Post
I was saying about pcb size, not price. Will the pcb fit in the case?
If he has big case, he can use big tall caps with no problem, but if the case is small...
From DIY viewpoint, size doesn't seem to be a problem. If the small caps are short, we can do stacking.
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Old 27th August 2009, 03:00 AM   #16
infinia is offline infinia  United States
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Originally Posted by underwurlde View Post
Great replies, thanks so far...

I understand that increasing capacitance = increased inrush etc etc.

going back to infinia's reply if I may:

OK, enlighten me: why is using planes NOT a good idea?

If paralleling many PS bulk caps you want to hook things up with the intent of controlling high charging currents w wide traces, and you want to take the output at the most quiet point of the circuit (ie closest to the last caps terminals). You also want to keep the input charging pulsing currents away from the output. The problem with using full planes ie no etching is you can't control this too well. Although you can use semi power planes with some simple strategic cuts/etches to isolate the input from the output tho.
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Old 27th August 2009, 03:13 AM   #17
star882 is offline star882  United States
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For high current applications, an array of capacitors that meet the required ripple current specifications are easier to find and sometimes cheaper than one large one with the same specifications.
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Old 27th August 2009, 01:16 PM   #18
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Am I correct in my assumptions: One massive (expensive probably) large cap with super low esr is what people tend to use. Open up a Naim and there they are glistening away in all their audio-like glory. But then to me they are 'spoilt' by the necessary wiring = inductance which will 'fight' the capacitance.... you really want the capacitor terminals right were the power is being taken from.. but this is going to be difficult with large caps, no?

So I think, use many small ones (surrounding?) the point at which they are needed on the PCB, thus legs are as short as possible. no need for fat wiring schemes. Also paralleling up many smaller caps = lower ESR (yes?). Also use of ground planes to me is inherently 'like a capacitor' i.e. 2 plates... you're also maximising copper tracking and any circular ground paths are automatically matched (a no-brainer in terms of tracking i.e. it's two planes)... the PCB thus becomes the capacitor perhaps, this capacitance being available to a greater area of need and is easier to design.

Just my (probably flawed) thinking...
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Old 27th August 2009, 03:54 PM   #19
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Your "PCB" cap will be in nF scale. It is not useful for power supply filtering/decoupling for audio. On the other hand, you can find many such usage in high-speed and RF circuits.
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Old 27th August 2009, 06:12 PM   #20
zlab is offline zlab  Hong Kong
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I have try a experience with a TP202, 2 X 4700UF rubycon capacitor sound better than 1 X 10000UF in a A/B/X test with my friendin a listening test.
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