sounds like you have a short. Kind of like tapping both ends together on jumper cables

 

There is a circuit breakers in the system, which would account for the sound and behavior, to some degree. I know of one that covers the accessories. It is located behind the driver's side kick panel. On my car it just covers the power seats, but I seem to recall it would also cover the power windows if you had them. Perhaps it would also cover the convertable top as well. If the radio is hot hooked up from the stock wiring, but to this circuit then you could account for the behavior. It would also mean you are overloading the circuit breaker with all that stuff running off it.

Circuit breaker is the dull silver thing box screwed to the body, dead center in the photo