Capacitor polarity?

[FrankenFretter***]

I've recently read that tone capacitors should be correctly oriented in their polarity, or there will be a high-end roll off. It seems like I read something about cap polarity here at some point, but my search didn't turn up anything useful. From what I've read, the outer foil lead should be toward the input (?) and the inner foil lead toward the output. I'm not sure what that would look like in a guitar control cavity. When I've replaced caps, I don't usually pay any attention to which end goes which way. In fact, I've never paid any attention to that. Am I missing something?

Thoughts? Comments? Suggestions?

I'm planning on changing the caps on some of my guitars, simply because I have some to fool around with.

[ibanezjunkie]

well, ive never done any electronics mods on a guitar i recall

but i did GCSE electronics, and i know for a fact capacitors need to be the right way round or it doesnt work lol

depends on the cap type, radial capacitors (like in computers, or most modern electronics and stuff) have one leg longer than the other, the longer leg being positive.

[jim p]

If the capacitor is connected to ground on one side then it is best to connect the outer foil to ground. This way the outer foil will act as a shield to reduce noise pickup. If not ground then which ever side is the lowest impedance if it was a coupling capacitor then the foil should be connected to the low impedance output not the high impedance input of the next stage.

[tunghaichuan***]

If the capacitor is connected to ground on one side then it is best to connect the outer foil to ground. This way the outer foil will act as a shield to reduce noise pickup. If not ground then which ever side is the lowest impedance if it was a coupling capacitor then the foil should be connected to the low impedance output not the high impedance input of the next stage.

Here is an explanation and tells how to figure out which side is connected to the outer foil:

http://www.aikenamps.com/OutsideFoil.htm

[Heywood Jablomie]

Sean, I don't have an expert to cite, but I'm pretty sure it doesn't matter in a guitar circuit. It's funny that it didn't occur to me when I rewired the Strat, but then again, there was no indication on the wiring diagram that came with the upgrade kit. Since there's a 50/50 chance that I soldered the cap one way or the other, either it doesn't matter, or I got lucky.

[bcdon***]

Ceramic capacitors are not polarized so there is no right direction (like a resistor). If you are using an electrolytic capacitor then the polarity is normally marked on the side of the can or indicated by one lead being longer than the other.

[sirnak]

@Ch0jin: That's a really great explanation on capacitors. I didn't even learn in this detail at college. I am just curious about something though. If I were to test a polarized capacitor's value on Capacitance measuring device. I haven't done this type of testing before so please bear with me. If I were to connect "+" of cap with "+" of device together and "-" of both cap and device together, I would get a certain reading. After that if I reverse the connection, I would certainly get some reading. Will these two readings be different from each other? How different will they be in terms of capacitance value?