I recently assembled a guitar I've been working on for quite some time, but when I plug it into an amp it produces a hum much louder than my normal amp hum... I thought it was a grounding issue at first, but everything seems to be properly grounded and shielded and whatnot. What's really throwing me is the volume of the hum changes based on the position I hold the guitar in, relative to the amp. I've tried it in a few separate locations on multiple amps, all with the same results. Does anyone know what the problem is/how I can fix it?
That has happened to me in a lot of places with all of my guitars. I think it's an electrical thing. Something to do with the circuit your amp is plugged into linking with lights or other interferences. That's the best assessment I can give anyway.
Sounds like a shielding issue. Do you have two amps hooked together? That could cause a ground loop if not properly dealt with. Other than that, are the pickups humbuckers or single coils? Sounds pretty standard for singles (depending on to what degree).
It is a shielding / grounding issue. You've missed something.