apd6847

Last night when I was hooking up my amp for my speakers, i had my radio on, playing music while i was hooking it up and then out of nowhere my radio cuts off and my interior buzzing noise came on (my key was turned on) and nothing but the battery light on the dash comes on. My headlights, emergency flashers, brake lights and starter works but my gauge cluster, radio ,cigarette lighter, reverse lights, dome light, A/C blower do not. I have checked ALL of the fuses and none seem to be burnt as well as the one on my amp and the one under the hood for my amp. Could this possibly be the starter relay?? Thanks, any help appreciated.