somewhat boring capacitor question

[jball85]

I read somewhere online that a capacitor's capacitance will change if it's voltage rating is exceeded. I was wondering if it also changes if the voltage is far below the voltage rating. Or should I avoid using capacitors with high voltage rating such as 630v and use say a 50v cap instead. would the lower voltage be a better option for building an average guitar pedal?

[madbean]

Over voltage will most likely damage or cause complete failure to a cap. Under voltage will not. Otherwise everyone's pedals would be ruined when they were unplugged from their power source!

Anyway, in the case of film and electrolytic caps, the general rule is the higher the voltage rating, the bigger the package. That's why we usually stick to 16-100v for most of out caps. An Orange Drop, for example, might be rated at 400v, but it will also be huge.

[CRBMoA]

16V 25V 50V 100V..............those are common.

630V are HUGE

Unless you exceed the ratings of your caps (quite hard to do unless you find some 6.3Vs or you are running something at 18V), you will not have any issues.

[jball85]

back to my original question though does anyone know what would cause the capacitance to change, could it be temperature? maybe that was what I read. Do any of you guys prefer using the larger and higher voltage caps in your circuits or is it subjective as usual?

[madbean]

I would expect excessive heat to damage caps in such a way to either render them leaky or totally useless.

Some caps can also be damaged be incorrect polarity, such as tantalum. Actually, they explode.

Bottom line is, there is no advantage that I know of using high voltage caps in guitar pedals. There is possibly some indirect benefit in the case of the actual materials used to manufacture it. Case in point, the Orange Drops I mentioned. They pretty much only come in high voltage ratings. The lowest I've seen are around 200v. I have a bunch of 560n ones that a freaking enormous.

Actually check that....if the higher voltage cap has a very low ESR, that could be advantageous. I bet you could find some info about voltage vs. ESR on diystompboxes.

[jball85]

one more capacitor question, If I were to use some 16v electrolytic caps in a pedal circuit would it be detrimental to run the pedal at 18v?

[madbean]

Over voltage will most likely damage or cause complete failure to a cap.

[bigmufffuzzwizz]

Over voltage will most likely damage or cause complete failure to a cap.

Which means it will blow up!