10V electrolytic cap

[MikeH]

I'm using a 10V electrolytic as my power supply filtering cap, do you think it will end up failing?  Or can it probably take more than 10V anyways even though it only says 10V?  And if the cap that's filtering you power supply fails, what can happen?  Other than some extra noise and poor performance with a dying battery.

[R.G.]

Electrolytic capacitors are rated for a surge voltage that is somewhat bigger than the long term rating. How much? it varies from maker to maker.

In the days of batteries only, 10V caps were fine. In today's world of "Kewl, it sounds better at 12V. I think I'll use 30V and see how kewl it is then..." it doesn't make sense to use 10V caps on 9V powered effects unless you just have to. I wouldn't use less than 16V, which is the next standard voltage up, and if you can get 25V in there, do it.

Do you recall how common it is to see posts from people wanting to run their pedal on 18V because it makes it sound like lasers or flying saucers?

If it fails, it could fail high leakage, and just drain your batteries. It could fail high leakage on an AC adapter and boil its electrolyte, spewing conductive gook all over the inside of your pedal. Or it could fail open or shorted.

[The Tone God]

It used to be that caps got smaller with voltage so in space constraint situations a designer would try to go as low as possible. This still applies today, as the universe still dictates the same rules, but the materials and construction techniques used these days has progressed enough with the likes of miniature caps that the physical size difference between the lower voltage and next couple of size voltage values is not really worth speaking about.

These days I don't use anything less then 16v and generally try to go as high as space and costs can allow. 10v IMHO is playing power chicken.

Andrew

[JimRayden]

Caps do have a voltage headroom/space ratio to help you decide on which to buy.

But every time I buy some diodes for a power supply, I'm always confused as which would be correct for the application. The 1N400x series all are one size and price. Extra voltage headroom would have no advantage when used with the particular unit I'm building. In that case, I guess it's the matter of delicately considering my choice by picking the highest value without it feeling like a parody of an overkill.

That's why I always buy 1N4007 for 9V applications. At least I won't have diodes failing on me if I accidentally use a tube amp's power supply or mere industrial voltage on my pedals.

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Jimbo

[Processaurus]

Boss uses the 10v caps for their power supply filters on alot of their pedals, I hear thats one of the more common things to fail with them. 

[oldrocker]

Would this apply to only electrolyic caps?  I just built the Mr. EQ (ROG) and used a 10v .47uf ceramic cap (It's what I had laying around).  It works good now but I'm wondering if I should replace that to avoid future problems.

[Mark Hammer]

For caps between V+ and gnd, use the next standard value up from the anticipated supply voltage.  So, 16v if V+ is never going over 9vdc.  A 25v rating might be preferable to 16v if the supply is going to be 12vdc or 15v.

BUT....

Not all paths in a circuit demand such ratings.  If it is an electrolytic cap in the signal path, like the cap between the output of an op-amp and a volume control, the anticipated voltages will be well below the supply voltage.  If it is the smoothing cap in a Vref subcircuit (where the supply voltage is passively divided in half for a "floating ground" and the cap is expected to see V+/2), then a rating well below the supply voltage is also reasonable.  Ths is one of the reasons why one might easily see a mix of voltage ratings in commercial pedals.

Punch line is that one should always use the voltage rating that gives an appropriate margin of safety and conformity to the stated spec/value.  That margin will vary on where it is used and the supply voltage.  If rating makes no appreciable difference ion cost or size, then for just about every pedal-related build people here might be interested in, a 25v rating will be just fine.  Kind of like the basic black shift if you're a woman, and the navy blazer, white shirt and grey flannel pants if you're a man; good for all occasions.

[Ronsonic]

I'm using a 10V electrolytic as my power supply filtering cap, do you think it will end up failing?  Or can it probably take more than 10V anyways even though it only says 10V?  And if the cap that's filtering you power supply fails, what can happen?  Other than some extra noise and poor performance with a dying battery.

Why not tell us how many volts are actually on this cap so we might have a possibility of giving you a meaningful answer. If you've just got it connected to a 9v battery it's probably fine. If you're using some anonymous wallwart all bets are off.

Ron