sound cuts out when the volumes turned up

[malevolence]

i installed a amp and a sub in my car i am running front right left from my deck only the sub is hooked to the amp when i turn the stereo up and it is hittin pretty hard the sound cuts out for a second and then comes back on not just the sub but all speakers. the face on the deck doeasnt turn off either like i typed just the sound is. is it a bad ground, i got the amp grounded to the nut in the back of the seat and the deck is grounded to the stock ground wire , that the original deck was hooked to what is the problem ...i know if the ground was bad on the amp the sub could shut off.right? or if it was the ground to the deck the deck face would shut off wouldnt it ? what would make just the sound go off in all three speakers ? is it the gage of wire im using perhaps or is it my alternator or battery not supporting enough juice when i turn it up .my headlights dont dim nor deck when its bumping either? could use a little insight

[GSteg]

take out the turn on remote wire for the amp so that the amp does not turn on at all. Now crank up your system and see if your speakers still cuts out. If it does, then your headunit is the problem.