Sourcing Caps

Hi all,

I was wondering what you look for when sourcing capacitors. Obviously, the capacitance value must match and it must be able to operate in the desired temperature range at the necessary voltage(s). Having a cap that is an acceptable size is important too. Tolerances are another thing to consider and should be equal to or better than the desired values.

I usually try to get caps of the same type as is asked for (ceramic, film, electrolytic, etc.), but have heard that it is okay to substitute different types sometimes. What are the big differences in the types of capacitors when it comes to sourcing?

Also, does the temperature coefficient matter much when sourcing caps for audio kits like the Shruthi?

Best Regards,
-J

The thing to watch for is that when and if you put ceramic caps in the audio path or as part of VCO/VCF circuits they have to be COG/NPO grade. Those have very low temperature drift.

When the circuit description calls for polystyrene or “Styroflex” capacitors it’s usually because these have very tight tolerances, 2.5% or better.

Temperature coefficient: not for filters ; but important for oscillators.

Check that tolerances are 2.5% or 5% at worst for anything used in filters.

These days good quality COG/NPO caps aren’t that much more expensive than poorer grade ceramics, so to reduce headaches - get those and only those.

@pichenettes: True - I got carried away there.

You can also throw caution to the wind if the caps are used as decoupling caps for ICs - anything goes and the exact value isn’t that critical either - anything that’s roughly the same value is good enough.