Since you are talking about, on the base side, an outlet having 120v / 20A, I'll assume you are talking about here in the States, as I don't know what's
going on with the rest of the world, but voltages and
amperages are
going to be different elsewhere.
The original radio is long
gone, replaced by a modern AM / FM / CD head unit and lots of
amperage, plus a subwoofer box in back.