Are they LED's?

 

yes sir custom dynamic

 

subscribed

 

Try one of the ground loop isolators right before your DSP. They work!!!

 

does the ground loop isolator effect the sound quality or anything

 

Not one bit. Just filters noise.

 

It does sound like a ground loop (GL). Even if you moved the fog light ground to the battery and still get hum you can (and almost certainly are) getting ground at the other end of the loop (somewhere along the signal path going to the amp and the light housing) and therefore have a voltage drop resulting in ground noise that in your case is audible.

A GLI, in this application, is basically a passive isolator (a transformer). It may very well attenuate the signal but will not likely effect frequencies in the audible range ... or it might (depending on quality). Further, depending on where the amp is picking it up (i.e. maybe through the amp chassis and not the RCA input) there is a possibility you will still have ground noise. In other words, these devices often work well, but not always. You might still have ground hum or an attenuated level (you'll need to turn up the volume more than you used to) or both. The only way to really tell is to put one in the signal path and see. It's certainly not expensive to try.

Just out of curiosity rather than ground the light to the battery try grounding the amp negative power lead to the frame and see how that works.

(while noise isolation is one reason to ground amps to the frame it is not the main reason I'm always bitching about it. I'll repeat it again. NOTHING should ever be grounded directly to the battery except the ground bonding strap, EVER. It's a dangerous practice.)

If you have an interest in understanding, finding, and eliminating ground loops this is an excellent whitepaper written by an MIT prof on the topic.