Angry llama squeal issue (solved)

[August]

Hi,

I’ve build an angry llama kit, but hear a high pitched squealing noise when the circuit is turned on. Any tips?

 

Things I’ve tried o debug: Reflowed all pcb connections, installed new electrolytic caps (not shown on pic), swapped ic, set bias voltage to 5.5V, battery powered the circuit & audio probed the circuit. Noise is already heard after R2… R3 is removed in the picture and it still shows my first trial with angled caps. This is now done with cleaner new caps (still angled because of component height)

 

Hope someone can help me 🙏

 

 

[Barry]

Make sure the Boost in the middle is not cranked. Not my circuit but it is called Angry for a reason.

If that doesn’t help and you have spare components you could try changing C4 from 100p up to 330p or 470p

[August]

Thanks for the help!

The building doc I used mention guitarpcb on every page so I thought this is the site to call for help 🙂

I’ll try to replace C4. Do the values change tone? I’ve seen pictures of this kit with tantalum caps instead of ceramics at c3 & c4. Would that help? Could be that I fried some components, my soldering technique isn’t perfect.

 

[Barry]

The value filters noise. Does not affect tone. Do not use tantalum.

When I said not my circuit I meant original design.

[Barry]

Also, just flip the switch and tell me if it goes away.

 

 

If none of that helps try something for me and just lift one leg of R9 (whichever leg is more convenient) out of the circuit and then try it.

[August]

It’s working!

As you mentioned c4 being the possible culprit/solution, I checked for remaining flux around that component. After some thorough cleaning of that spot + the rest of the pcb I taped the pots and underside of the pcb with electrical tape to insulate them.

I also cut the wire from ground out to the jack, as I read this could cause a ground loop. Jack is already grounded via metal housing.

This fixed the noise!

Thanks for your help and suggestions, by analysing the circuit I now also understand how the different stages work. Really happy with the pcb and your quick response ❤️

On to the next pedal, the SWAH

[Barry]

I am glad you got it sorted out. Thanks for reporting back.

A quick tip when building pedals is to remember that the pedal itself is only one part of the overall signal chain. Things like pickup output, guitar type, amp settings, power supply, and even playing style can all have a significant effect on how a pedal circuit responds.

With regard to the SWAH, this is one of those circuits that really needs to be dialed in to your particular guitar and setup. In short, it is not going to “quack” on every setting combination. You will need to spend a little time finding the settings that work best with your rig.

Oh, and always bend the leads on glass diodes with pliers and not your fingers. The glass can crack and ruin your project.

[Author]

Posts