Trying to fix amp noise

[Italianhawksfan]

Hi all, I recently installed a JBL 4 channel amp in my car, and four JBL speakers as well. But when I turn the volume from 0 to 1, the amp noise can be heard. If I turn the volume up more than that, the amp noise level remains the same, but the music gets louder. Here is a schematic of how my audio system is set up, I followed the step by step advice at crutchfield also, so I'm not sure what exactly is causing the noise. Any insight would be greatly appreciated, and if you need pictures of anything, I have the interior of the car taken out so that would be no problem. Thanks!