93 Camry radio problems

I have been having a problem with the radio in my 93 Camry Wagon. It will play normally for a set amount of time and then act as though all the speakers are blown (crackling sound from all speakers). After sitting awhile it will return to normal and then freak out again. It is the premium package I believe with a stacked radio ,cd, and tape player. Could there
be an amp involved that is intermitantly shorting? Can you replace this set up with a normal aftermarket head unit? Any info appreciated.