Sub Feedback?

Question

So when I turn on m car everything works fine, then i turn up the stereo and My subs go from working right to making a loud continuos note. Is this feedback or something worse and how do i fix it.

Also, the "feedback" stops when i turn it back down. I have tried everything i can think of and it still wont turn up very loud. And i have already tried turning down the gain. it didn't help much.

Answer 1

They say proper grounding may help.  The negative circuit  coming from the outside rca input jack on my amp on the inside was broken in half. I bent mine in a manner where it touched the piece it was broke from and no more hum.  Check those Rca cables.  Do they still hum with another amp and same rca cables connected.  Un plug 1 cable then the other.  Any conclusions?