Thanks, my last hope is that it’s a ground loop on the power cable. I petty well eliminated everything else. It does sound like a hiss but I can detect a slight change when I move the amp. I'm going to hook a separate battery up to the amp right next to it to see if the noise reduces some. The power line is running next to the wiring harness. This did cause some noise in the RCA cables so I moved them. I might need to move the power cable too.

I've been looking for a filter that would hang off the power line and eliminate the noise. But all I can find are inline power filters and I'm afraid they might not handle the current.