The description you give appears to be 60 Hz Hum, coupled to the Audio.
You could insert Filters at the Power Supply for Noise Rejection, but the easiest (and less expensive) method would be to purchase a "Cleaner" Power Supply.
There are several Members who will have much better suggestions than mine, so feel free to hang around!
-- Scott
Scott " 35 " Thompson Just Say NO To Green Eggs And Ham!
