electronics problem

[Steve Tyssen]

Hey guys how's everything goin ??

I'm just wondering if anyone could help me out...  I've wired up a few CBG's successfully but lately i've been having a few problems with humming / feedback..

I'm just using a piezo buzzer with a volume control and of course a 1/4" input jack.   For some reason when you plug the guitar in, there is a slight humming sound.  When you touch the volume knob with your hand the humming sound is really maximized.  And what seems even weirder is that when I touch the metal on the guitar lead / input, there is a dead silence with perfect response from the Piezo.  

I'm just wondering if anyone has experienced this or if it's a common issue!??  I've got a couple of pictures on my page that show you exactly how I've been wiring them up.  Thanks in advance!!

[Outhouse Instruments]

Mornin.
This is one reason I don't use controls on my boxes. I let the amp do all the work.
You need to make sure the case of the control pot is grounded to the jack.
( After checking your pics, below is what you need)
May even need to ground the strings as well. Do this by drilling holes in a metal plate and placing it where the string ball ends are.
then run a ground wire from the plate to the jack.

Matt

[Tracy Kennedy]

Is it possible the tang on the 1/4" jack is not properly ingaging the input?

[Roy E. Queen]

I'm pretty sure Matt nailed it. Anytime you have noise like that that and it goes away when you touch something else it's a grounding thing. Test it by using a couple alligator clips with wire jumpers on different spots to see when it goes away.