Wah Pedal Whine

[tommycataus]

Hey guys, I built a wah pedal from scratch and it works as intended with a battery, but with the power supply (it's a cheapie) it whines when in the toe-down position. I've wired in Dano's Huminator circuit (Beavis Audio) but it doesn't seem to be doing the trick.

Please could someone diagnose the problem? I think half my problem is that I don't know whether it's buzz, hum, whine or whatever as I've only read about these strange phenomena, not heard them. I'm not sure whether it could be a wiring issue - my off-board wiring is still rather amateur and I've not used shielded cable in any of my builds yet. Any ideas?

[smallbearelec]

As shown, the Huminator doesn't add enough filtering to properly clean up a wall wart. What you want is a fairly large filter cap, like 1000 mf., followed by a 7809 three-terminal regulator, followed by a 10 mf. output cap. My Small Wart 125:

https://www.smallbearelec.com/Projects/SmWart/SmWart.htm

shows this on its output, only you don't need the resettable fuse because the wall wart has its own current limiting.

[Paul Marossy]

Inductor based wah circuits are about like guitars with single coil pickups, they are very sensitive to any EMI around them even though in a metal enclosure. Put a conventional transformer based wall wart real close to your wah pedal and you'll see what I mean. A power supply with a bunch of ripple on it will only make that stuff worse.

[tommycataus]

Thanks guys. On a personal note it's kind of awesome that I've been checking both your sites for some time now and reading info/making purchases, and you've both managed to help me even further now. Just goes to show how fantastic this community really is

I've experienced interference with wah pedals and single coils before, acting like a transmitter to bring me strange and wonderful radio stations from beyond the ether. However, that was only when high volume/gain was applied. I'll definitely take your advice and re-work the filter circuit. Voltage regulators have been added to the everlasting shopping list...

Thanks again!

[Paul Marossy]

Thanks guys. On a personal note it's kind of awesome that I've been checking both your sites for some time now and reading info/making purchases, and you've both managed to help me even further now. Just goes to show how fantastic this community really is

Hope you found something useful at DIYG.