multi cap can vs individual?

[iknowjohnny]

Is there a general consensus as to whether it's better one way or another? I need to replace a JJ 20/20/20/40uf can and i was wondering whether it's better to use discreet caps instead.

[xtian]

The only tradeoffs I'm aware of is price (usually individual caps are cheaper) and grounding (all sections share the same ground, so you can't run preamp grounds separately, e.g.). On the plus side, the can package is convenient and can save a lot of interior chassis space.

[Milkmansound]

my personal cutoff is 40W - anything more than that and you may want to run the reservoir caps to a different ground point. Under 40W I say go for it!

[gingertube]

4 caps in one can places a limit on the ripple current rating of them all. Ripple current rating depends on self heating and getting rid of that heat.

The 4 caps are concentrically wound. One of the caps will be identified as the "outside" one. That should always be used for the first cap in the power supply (straight off the rectifier) as it has the best cooling and hence the best ripple current rating.

Because self heating is a Power = current squared x Equivalent Series Resistance (ESR) thing then doubling the ripple current rating will give 4 times the expected lifetime (tripling will give 9 times etc.), so this is not a trivial arguement.

It is almost certain that the multicap can will have shorter lifetime than individual caps and for that reason I tend to avoid them.

When restoring amps with a multicap can I leave the cans in place so as to not change the looks but cut the connections to the caps and mount individual cap replacements under the chassis.

Cheers,
Ian

[xtian]

The 4 caps are concentrically wound.

Wow! Didn't know that. Great info, Ian.

[Structo]

A while back we had a capacitor thread and some guys dissected some cap cans.

Inside were radial caps that may or may not be the right values printed on the can.

Same with some axial caps, inside were radial caps.

I have read before that due to the grounding of the cans, they tend to be noisier than individual caps.

[Leo_Gnardo]

The 4 caps are concentrically wound. One of the caps will be identified as the "outside" one. That should always be used for the first cap in the power supply (straight off the rectifier) as it has the best cooling and hence the best ripple current rating.
Cheers,
Ian

That's very enlightening & thanks very much Ian. Now . . . how does one know which is the "outside" cap? And do the manufacturers of currently available can caps still do it the same way? JJ? CE? F&T?

[iknowjohnny]

Interesting. See, even tho i've always heard a lot of people citing no difference, this is why i often ask questions like this. One person who happens to know something few others do might see the post and add some good info i never would have found out even googling it. Thanks !

[M Fowler]

That cap noise must be acceptable since a lot of Marhalls and others use them.

I find no difference myself.

[iknowjohnny]

That cap noise must be acceptable since a lot of Marhalls and others use them.

I find no difference myself.

True, but i was talking multi cans like the JJ with 4 caps in it. Marshalls use 2 caps per can

[M Fowler]

Okay I'll rephrase that Fender Princeton Reverbs used 20/20/20/20 and they sound great.

I use JJ 40/20/20/20 caps quite often.