System consists of 2 US Amps MD3D's, 2 AQ HD3's and a Kenwood KDC-X891. Alright I will be playing my system bumping it hard and all of a sudden my bass will cut out. I do not think it is the HU because the mids and highs continue to work. The bass will come back on when I turn the volume down or if I leave it playing for a few seconds. I do have electrical upgrades: 220A alt, 1100A batt under the hood, big 3 done, and 3 Deka Intimidator 9A31's in the back. Why is my bass cutting out. FYI the HU does have a ground problem meaning that when I play a CD I have turn on noise and a thump when changing tracks, none of these noises occur when I listen to the radio or my USB source. So once again why is my bass cutting out.

Have you actually checked the voltage at the amps?

voltage stays around 12.5-13v