Power supply filtering for vintage pedal.

[Kinki fuzz]

Well, maybe not very vintage, but whatever. I got a Colorsound wah (sweeeet sound) that had only battery option. I drilled an added jack for external 9v supply. With some power supplies I get an annoying  "wweeeeeeeee" in a certain pedal position.
I realized the pedal has no power filtering (as it was only intended for batteries), so I thought I could add a little board with a filter.
Does that make sense?

I think a 100u electrolytic cap and maybe a polarity protection diode. Enough? Or should I add something extra?

Thanks guys!

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[rullywowr]

Try a 100u and 100n across the power supply.  You are on the right track. Nice pedal dude.

[Kinki fuzz]

I will!,
Whats the 100n for?
Thanks!

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[midwayfair]

Whats the 100n for?

Polyfilm capacitors are better at filtering high frequencies than electrolytic capacitors. It's best to use a mix of capacitor types for filtering in some cases.

[davent]

Also put a small resistor in series before the caps, 100r is usual for low current demand circuits.

This from Beavis Audio


More info here. http://www.diystompboxes.com/smfforum/index.php?topic=80063.msg661860#msg661860

[Kinki fuzz]

You rule dudes, thanks!! Now I know what to do.... and also why and how it works.
Rad.

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[davent]

Should add, take power for your LED from before the 100r resistor as  a power hungry LED could cause a drop of a couple volts across the resisitor and you don't want that.
dave

[Kinki fuzz]

No led for this one, but good to know!

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