Strange "wind blowing" kind of noise

sixthfloor · Post by **sixthfloor** » 26 Feb 2018, 16:00

Hello guys,

I've built some time ago a Dirty Sanchez (modded BE-OD) from pedalPCB. Worked absolutely great until a couple of days ago, where it started to make a strange sound similar to wind blowing. Here's an audio of it :

Any thoughts as to what might be the cause ? I checked and/or changed all the components I socketed (ICs, diodes) just to be sure, but it didn't solve this.

Thanks by advance

Frank_NH · Post by **Frank_NH** » 26 Feb 2018, 16:21

Check your connections (sounds like it may be a loose wire). You may also want to reflow your solder joints. I that doesn't do it, I'd check all of your components (especially capacitors), although I'm not sure why components in a new build would suddenly go bad.

sixthfloor · Post by **sixthfloor** » 26 Feb 2018, 18:04

Thanks for the quick reply Frank, much appreciated. I've reflowed any solder joint I found dubious, to no result though.

The build's about six weeks old, I guess that qualifies as new ?

Checking the caps will require to remove them from the board I guess - my multimeter doesn't manage to read their values when they are soldered. I might try with the electrolytic caps as there are few of them.

Frank_NH · Post by **Frank_NH** » 27 Feb 2018, 15:22

Yes, unfortunately checking components that are soldered can be a pain. You might also make use of an audio probe to see where the signal suddenly becomes noisy.

https://www.diystompboxes.com/pedals/debug.html

sixthfloor · Post by **sixthfloor** » 27 Feb 2018, 18:27

Great idea, I'll build a probe and try to track the noise down.

sixthfloor · Post by **sixthfloor** » 07 Mar 2018, 14:04

So, I started tracking the noise, and it appeared in the gain stage corresponding to the gain pot. In fact it was as if the gain pot was giving around 2M resistance under whatever setting. So I changed the pot a couple of times, to no result - checked the wires and solder too.

In the end I "externalized" the whole gain stage on veroboard to make it work

There must be a problem somewhere else in the circuit though, as there is a high-pitched noise when the gain is cranked via either the gain pot or the internal gain trimmer.