Audio Systems: Sony car stereo, sony car stereo, amp off

Question
My stereo keeps cutting off when I turn the volume up.  I thought it was my amp, but when I took the amp off the stereo still cut off when I cranked up the volume.  Any and all suggests I will try. HELP!!!

Answer
A few possibilities, use fade/balance and try just fronts, just rears, just lefts, just rights, and see if it always does it. Then try each
one by itself. If only one does it, you have a speaker shorting out. If it makes no difference, the deck may have a loose connection, a bad internal solder joint, or the voltage in the car is dipping below 11 volts. Do the headlamps dim when you crank up the volume at idle? How about at highway speeds? How about other sources? AM/FM/CD/MP3...etc. Perhaps only one source cuts out, that info could be help.