Several people have noted that they use the same external supply from
Radio Shack that I tried, and without a noise problem. This makes me
wonder if the problem is with something *other* than the power supply
itself. Is it possible that the copper wires running from the binding
posts of the power supply to the spring clip terminals on the rear
panel of the R8B are the real problem? In other words, could they be
acting as antennas and picking up the noise I hear? If so, then the
problem would persist no matter which external power supply I used.

Steve