I've built tons of pedals, and thought it would finally be nice to have an audio probe so I don't have to fire up the signal gen and scope. I made one with the little board available here, and use it as the photo shows. It works fine, when the probe is touching a component, and in also in bypass. But- when the probe isn't touching anything, there is a loud buzz. Is this normal for an audio probe? do I not have something grounded? I did initially solder the jacks backward, and when I reversed them I broke the pad off of a connection. I just ran a wire to replace it. Same as if the trace was there.
Possibly EMI
My homemade one does that if I have my florescent mag lamp on and over the desk which is often when probing for me as my eyes aren't what they used to be...
When not probing, it's an antenna
Try turning lights and nearby electronics off and see if it goes away.
Not sure what the kit is here but if you find that it is EMI and you can't relieve it or live with it, you could try using a shielded wire and ground one end of the shielding. A scrap of guitar or mic cable would do. Or some flexible coax.
I'm just using an old DMM probe that I hacked a cap into.
+1. My overhead magnifier light does the same thing. I turn it off when testing unless I really need it to see stuff (I'm a dinosaur).
This makes sense. I'll try cutting down the emi. I am also using an old dmm probe I cut the end off of. Thanks