quick cap question

[JimCOX]

Hey guys,
I'm writing up my bill of materials for a sho clone.
Now can i sub a 10uF/16v for a 10uF/50v

Thanks

[MarcoMike]

definetly yes...

that voltage is the  maximum rated voltage, which means the voltage a capacitor is able to withstand. as you're probably operating your sho at 9V, anything above that would be ok.

generally (well, not in all cases... ) the smaller, the better.

[JimCOX]

Ah okay thanks, I thought that. It just seems a little odd how they put it as 50v.
Well thats saved me a couple of quid

[R.G.]

Capacitor voltage is a withstanding voltage. In general, you need capacitors with a rated voltage of a little more than the circuit power supply. It's false economy to try to use very low voltage caps in (for instance) a 9V circuit where the cap only sees a voltage of 3V or so. So in general pick 16V or 25V caps for a pedal circuit because there's going to be some genius with BUMS that feeds it 12 or even 18Vdc where it was designed for 9.

The cap makers have noted that it's cheaper to make one thing than several, and in some cases only offer higher voltage caps where the cap is small. The 1uF cap is an example. It's hard to find a 1uF electro in anything under 50V. The makers think "hey, 50V works for most of these and it's cheaper to only offer one, in high voltage."

That's why you can't find low voltage ones in the low capacitance ranges.

[amptramp]

This is the military handbook for reliability calculation:

http://www.barringer1.com/mil_files/MIL-HDBK-217RevF.pdf

Go to page 134 of the pdf and you will see the effect of voltage stress (volts in circuit divided by rated volts) and you will see that the higher voltage rating on a cap willl extend its life.  There is a factor of

(S³/0.5) + 1

If you are trying to find out about reliability of specific devices, the MIL handbooks are the wisdom of the ages available for free.

[MarcoMike]

what I meant with "the smaller, the better" was actually just referred to cost and board space.

in a circuit as simple as SHO is I guess there is no need for mil spec and extended life... that cap will see no stress at all! and in that case I would go for a film cap... (did I ever mentioned I work in a film cap company??  )