Chevrolet Repair: Radio in Chevy Impala, chevy impala, chevy truck

Question
I have and they are all OK. There is power to the radio. It is on - just no sound. Is there separate power to the speakers in this car? Could it be the wiring harness?

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-----Question-----
I have a 2001 Impala. The sound on the radio has completely gone out. I have replaced the radio and still no good. It seems to be a speaker problem. How can I diagnose it?
-----Answer-----
Have you checked ALL the fuses? Is it getting power? Does it have a c.d. player. Have you looked in the manual to find ALL the fuses?

Answer
I was trying to remember a friend of mine that owns a chevy truck that had the same problem. He either checked a fuse under the hood or disconnected the battery. Is there a big plug in the back of the radio for the speakers or was the radio installed by cutting and trimming wires?