madbeanpedals::forum

General => Open Discussion => Topic started by: Kinki fuzz on May 16, 2014, 09:00:04 AM

Title: Power supply filtering for vintage pedal.
Post by: Kinki fuzz on May 16, 2014, 09:00:04 AM
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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Title: Re: Power supply filtering for vintage pedal.
Post by: rullywowr on May 16, 2014, 01:02:36 PM
Try a 100u and 100n across the power supply.  You are on the right track. Nice pedal dude.
Title: Re: Power supply filtering for vintage pedal.
Post by: Kinki fuzz on May 16, 2014, 01:42:35 PM
I will!,
Whats the 100n for?
Thanks!

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Title: Re: Power supply filtering for vintage pedal.
Post by: midwayfair on May 16, 2014, 03:39:55 PM
Quote from: Kinki fuzz on May 16, 2014, 01:42:35 PM
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.
Title: Re: Power supply filtering for vintage pedal.
Post by: davent on May 16, 2014, 03:59:14 PM
Also put a small resistor in series before the caps, 100r is usual for low current demand circuits.

This from Beavis Audio
(http://www.beavisaudio.com/techpages/PoweringPedals/VariousPSUFilters.gif)

More info here. http://www.diystompboxes.com/smfforum/index.php?topic=80063.msg661860#msg661860
Title: Re: Power supply filtering for vintage pedal.
Post by: Kinki fuzz on May 16, 2014, 06:16:08 PM
You rule dudes, thanks!! Now I know what to do.... and also why and how it works.
Rad.

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Title: Re: Power supply filtering for vintage pedal.
Post by: davent on May 16, 2014, 07:27:34 PM
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
Title: Re: Power supply filtering for vintage pedal.
Post by: Kinki fuzz on May 16, 2014, 07:55:39 PM
No led for this one, but good to know!

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