Capacitors

[JohnnyPunk]

Hey all,
Is there a difference between film box capacitors and ceramic and electrolytic? As can one be used instead of another?

 

[Laundryroom David]

Hey all,
Is there a difference between film box capacitors and ceramic and electrolytic? As can one be used instead of another?

Yes
Sort of but not entirely.

Film and ceramics are not polarized. I have subbed them for each other with no ill effect.

Electrolytics are typically polarized. There’s a negative and positive terminal.

Some electrolytics are not polarized.

If you have specific substitutions in mind, you might want to ask about those. Some components are more suited to certain uses than others.

 

[Feral Feline]

Further to the Keyboard Cowboy's post, @JohnnyPunk, there are preferred places for some of these types.

In a Muff, for instance, 100n Ceramics were used by EHX in days of old.
Nowadays it's more likely to be a 100n Film cap, as the signal to noise ratio is likely better with Film — yet some DIYers will still build a Muff with 100n Ceramics to be period accurate to whatever Muff variant they are building because it won't sound right otherwise.

About as debatable as Hannibal Lector having an Amarone (originally in the book) to accompany his Census-Taker's liver with fava beans, as opposed to a Chianti as referred to in the film, because the film-producers thought not enough of the film-audience would know what Amarone is and why it pairs well with offal (such as liver and hunted game).

Generally speaking:


Small value stuff, ex 30p-120p
Ceramics

Medium value, ex 1n–1µ (can be as big as 2µ2 or even 4µ7)
Film Box


Big Value, ex 1µ–100µ
Electrolytics


What scale p <> n <> µ?

100 pF =	.10 nF =	.00010 µF
100,000 pF =	100 nF =	.1 µF
1,000,000 pF =	1,000 nF =	1 µF

As you become more familiar with building, you'll get a better feel for when to use what.



Thp-thp-thp-thp-thp...

 

[DeadAirMD]

I've found that capacitors have the biggest effect on the tone of the pedal. Since they all test so wildly different (some are +/-20), I make sure I always test them before putting them on the board. Big fan of adding capacitors to a dpdt toggle to have different tonal options when building a pedal. They act basically like a poor man's EQ.

 

[fig]

Pay very close attention to package size, else you'll wind up with a healthy supply of too large capacitors for pedal-building.
The datasheet will supply you with the lead-spacing, height and width.

 

[Feral Feline]

Yes to Fig's post above. I can attest that 600v 220n mylars will not fit most builds.

 

[MattG]

They are less common, typically larger and more expensive, but there are also silver mica capacitors. These are typically found in very small capacitance values, i.e. in the pF range. I prefer these to ceramics when space and budget allow.

Note that within ceramics, there are non-trivial performance differences for the capacitor's chemistry. For audio applications, I try for C0G/NP0 when possible, but like silver mica, these are usually available only in fairly small values. X7R is probably the most readily available ceramic chemistry, but their actual capacitance drops with an increasing voltage offset. One strategy to overcome that is to buy X7R ceramics with a voltage rating that is much higher than what the application requires (I try for 100v rated X7R ceramics for pedals). I can't find it now, but I read an article once that suggested the physical size of the ceramic also can impact the voltage offset issue, and larger is better.

And in the higher value space (1uF and above), where electrolytics live, there is also tantalum. These are also polarized like (most) electrolytics.