Overdrive/distortion pedal sounds good, but single notes oscillate

[Ryanhardy]

I currently have a overdrive style peal layed out with clip cables.  The distortion is by way of diodes to ground.  But when picking single notes there is a strange oscilating noise, but i noticed it disapears when i touch the star ground point.  So the noise is only really a problem if playing open notes and not touching the strings which is rare but still possible.  Any ideas on how to prevent this oscilation without touching the strings?

[Plexi]

I would check all the ground points...
Or maybe some shortcut to ground.

[Plexi]

Any schematic/layout ?

[Ryanhardy]

Yeh ive checked ground.  But its almost like i need a "dummy ground", that grounds the circuit while not touching the guitar strings.

[thermionix]

One possibilty, just a guess as I haven't heard it, is intermodulation between the note you're playing and the normal hum that comes from a guitar when you don't touch the string ground.  In other words, not a malfunction.

[Ryanhardy]

Any schematic/layout ?

Its handdrawn and messy.  I can barely read it myself.  Is there some kind of component that will simulate the grounding effect of touching the guitar strings with my hand?  Grounding is one of those mysterious things i guess.  Some say to seprate signal and power grounds, etc.

[Ryanhardy]

One possibilty, just a guess as I haven't heard it, is intermodulation between the note you're playing and the normal hum that comes from a guitar when you don't touch the string ground.  In other words, not a malfunction.

I think you could be right.  But how to elimnate it.  Dont get me wrong.  If im gonna have noise id rather have oscilation than hiss, but it is a little annoying.

[thermionix]

I think you could be right.  But how to elimnate it.

Leave your palm on the bridge when letting an open string ring.

[Ryanhardy]

I think you could be right.  But how to elimnate it.

Leave your palm on the bridge when letting an open string ring.

This one made me laught but guess your right.  Simple fix.

[reddesert]

In a normal guitar (no effects), especially if unshielded, local electromagnetic interference causes hum that is damped when you touch the grounded strings.

Circuits laid out with clip leads can pick up a lot of interference.

Your problem might be a bad ground, or it might be a high gain circuit with a lot of clip leads that is subject to either local EM interference, or the leads are actually picking up noise from the circuit itself. Try either putting the whole circuit in a grounded box (like a big metal pot) to shield it from the outside, or wiring it with much shorter wires.

[Ryanhardy]

In a normal guitar (no effects), especially if unshielded, local electromagnetic interference causes hum that is damped when you touch the grounded strings.

Circuits laid out with clip leads can pick up a lot of interference.

Your problem might be a bad ground, or it might be a high gain circuit with a lot of clip leads that is subject to either local EM interference, or the leads are actually picking up noise from the circuit itself. Try either putting the whole circuit in a grounded box (like a big metal pot) to shield it from the outside, or wiring it with much shorter wires.

That has been my experience with hum/hiss noise.  When putting the circuit in a normal stomp case the hum/noise is reduced quite a bit (due to shield and shorter connections i suspect, as wooden cases also work).  But this noise is different, possibly Inter modulation as poster above said.

[GibsonGM]

If everything is designed and constructed well, there isn't much more you can 'know' until you place the circuit in an enclosure with short lead lengths, whatever power supply it will use, etc.      Chances are that this will go away once that is done.

Posting a schematic of what you built would get you much better answers, Ryan - we may see a fault in the Design rather than the fact that you have flying leads everywhere right now (a MAJOR way to create and pick up noise, interference - JUNK that can interact with your circuit!).   

The leads are antennas right now since they are not in a grounded enclosure, thus it is nearly impossible to diagnose a problem this way.

welcome to the forum   

[antonis]

Posting a schematic of what you built would get you much better answers..

Like "use a connected to star ground wrist/ankle band"..??


Sorry Ryan, just want to tease Sir Mike a bit..