lots of parallel caps, why?

[JojoD818]

Hi everyone,

I just listened to a Carver AV-64 and was pleased with it's sound. Looking through the chassis, there seems to be nothing special about the power amp's circuit but I did noticed an array of 1,000uf capacitors, 10 per rail, for a total of 20 pieces.

My question is why use 10 pieces of 1,000uf caps when you can use a single 10,000uf capacitor? Does it have to do with ESR? Or whatever it is called? Any advantage, disadvantage?

Best regards,
JojoD

[Magura]

Low ESR and price as far as im concerned. In some cases you can get higher ripple out of a bunch of smaller caps than from one big cap.

MAgura

[JojoD818]

Low ESR = good? High ripple = bad?

Did I get it right?

JojoD

[crown300]

ESR and cost, possible size constraints also.
There are many threads here on ESR - Effective Series Resistance - and its pluses/minus.
Rod Elliot has a good artcle on it here:
http://sound.westhost.com/power-supp...apacitor-value
go about 2/3 down to:Capacitor Ripple Current

[Magura]

Ripple capacity for a cap is the current you can draw from them, naturally limited by the esr as well.

MAgura

[KlausB]

Hi,
besides capacitance, every electrolyte cap has resistance and inductance . Bigger electrolytes tend to have higher inductances, smaller caps lower inductances.

By paralleling similar caps you add the capacitances, while the over all inducance equals cap inductance / number of caps.

So by paralleling 10 caps you only have 1/10 of the inductance.
Also the cap resistance is reduced. Hence the parallel setup may deliver more current faster.

Cheers
KlausB

[millwood]

Originally posted by KlausB
So by paralleling 10 caps you only have 1/10 of the inductance.

Cheers
KlausB

really? you can reduce inductance by paralleling them?

[sam9]

I suspect the more prosaic motivations: cost and space.

From my own diy experiece I conclude that sometimes many smaller caps cost less than fewer big ones, this may be even more the case when you buy in industrial quantities.

Secondly, many small caps can sometimes be packed in to the volume of an enclosure more easily than a few large ones. The opposite can be true depending on the dimensions of the enclosure and the other components.

[mrfeedback]

An ME amplifier model (850?) runs 100 x 3300uF caps in the psu (330,000uF total).
Limitless psu current capability and it sounds like it too.

Eric.

[Magura]

It is true that you divide the inductance by the number of caps by paralelling them.

Im though sure that the inductance of the caps in a powersupply is not an important factor....ESR is though.

As stated before...i agree (unfortunately) that its for prosaic reasons that many smaller caps are used instead of one big cap.

I use big caps with a film cap in paralel.....works as good as anyone could ever ask for. If you want something better than that, use a regulated power supply.


Magura