Power Supply Filtering

[frankie5fingers]

I was reading a couple of posts from a feller that was having some with a hum emanating from a type of power supply.  I've had that trouble now and again, even with commercially producted pedals.  Brian suggested adding a470u and 100n in parallel between the + and - as a power supply filter.  My question; would this not be a good idea for every build as a precautionary measure - to ward off evil spirits?  Would the values always be the same, or would you modify according to the circuit?
Thanks, Frank

[culturejam]

A larger power supply filter cap is part of just about every effects circuit. It's generally 100uF, but it may also be anything from 22uF up to 470uF. The smaller cap (100n) is frequently omitted, but it's certainly not a bad idea.

[mgwhit]

After I recently got schooled on the 100nF filtering cap, I've added a 100nF and a 100uF as a constant filter on my breadboard with no ill effects.  If a circuit board doesn't have a space for the 100nF, you can probably just wire it across the lugs of the power jack.

[jubal81]

I've read the 100n needed to be as close to the opamp as possible. Haven't tried it any other way for comparison, though.

[derevaun]

Tangential piggyback question: how big is too big? I have some random high-uF caps (+1000uF) and often wonder, when I encounter them, how they would work in that role.

[stecykmi]

Tangential piggyback question: how big is too big? I have some random high-uF caps (+1000uF) and often wonder, when I encounter them, how they would work in that role.

values that large are typically used in rectifier circuits, ie changing AC into DC. you certainly can use them, however, they're just much larger than what's typically used.