No sound. Bad amp?

[zonepro77]

I was wondering if anyone else has encountered a similar problem, and if so, what is the fix. I was driving into work yesterday and had my radio on. All of a sudden, all the sound stopped coming from the factory speakers. At first I thought it was the radio, so I changed channels and sources, but nothing worked. I also noticed the blinkers, back up sensor, warning chimes and bluetooth were also not even making any noise. Since then, sometimes its on and off every few seconds, sometimes it works for a while, and other times it's out for a while. I've narrowed the problem down to the factory amp. I installed an aftermarket amp for my sub, and they is still working fine and producing sound. I tapped into the factory amps inputs to get my signal for my amp, so I know it is not a signal issue. I also checked the amp fuse in the fuse box in the trunk and that is fine. So I'm thinking it's one of three things. Either there is an issue with the factory amp's power, the ground, or the amp itself is just bad. Any information anyone has would be helpful. Thanks!