i have a 92 oldsmobile cutlass that i am installing an amp and speakers in(the rear, the front ones im keeping stock)

when i was working on it the other day i cut the old speaker wires in the back and was doing some other things and went to check the front speakers to see if the radio was still playing and i only heard pops when my friend rubbed the amp power cable against the battery..

is it my head unit? i was thinkin that i just needed to fixe the wires..

please help..

Ronnie

P.S. I need to plug RCA wires into my stereo to plug in the the amp..is there any way i can do this without having to buy a new head unit?