Does running capacitors in parallel increase voltage rating?

[trjones1]

Is there any way to combine caps to get higher voltage rating?

Alternatively, if I'm running a pedal at 18 volts, does it matter if the input cap is 16v?  It doesn't seem like the voltage going through that cap ever gets close to 16v.

[CynicalMan]

Parallel doesn't increase voltage rating because the voltage over a cap doesn't decrease when another is placed in parallel with it.

The input cap probably receives less than 16V, but if you accidentally short a wire or it gets a weird input or another component breaks, that capacitor could pop.

[teemuk]

Is there any way to combine caps to get higher voltage rating?

Parallel connection, no. Series connection, yes.
...but note that series connection will also decrease the capacitance to 1/(1/C1+1/C2) so e.g. two 10 uf caps connected in series will effectively mean only a 5 uF capacitance. You also want to make sure that DC voltage is actually being dropped evenly across the capacitor terminals so you might need to e.g. wire a resistive divider across the series connected capacitors and then connect the interconnecting nodes of both the resistive divider and the caps together (see the power supply of many tube amps for example).

If you are talking about potentials of 16 volts or so then it's just way easier to actually buy caps rated for the proper voltage. Series connecting starts to make sense when we're talking about voltage ratings of  > 100 V.

Alternatively, if I'm running a pedal at 18 volts, does it matter if the input cap is 16v?  It doesn't seem like the voltage going through that cap ever gets close to 16v.

What the highest voltage at the input? Rate the cap accordingly. If it doesn't get close to 16V then you can use a cap rated for 16V.

[igerup]

It's only when you get close to passing > 450 volts that series capacitor connection is beneficial. Caps rated for more than 550 volts are not easy to find, so if you go crazy and decide on a Class B guitar amp with > 800 volts on the output tube anodes, then series caps is the way to go. I wouldn't want to carry that amp to a gig, it'd be really big, bulky and heavy.

[trjones1]

Thanks for the responses.  I have a bunch of 16v caps and I want to start experimenting with 18v power supplies for one of my pedals, but I'm not planning on making any part orders anytime soon. 

Reading the responses I'm starting to think that I don't really need higher voltage caps for my use.

[earthtonesaudio]

When using a series string, be careful.  Two 100V caps in series does not guarantee a 200V cap.

Use the equation:

q=CV

Find the total q and use that to see what the voltage on each individual cap will end up being.