I received this device at no charge from a relative's estate sale, so in good conscience, I cannot sell it. It is available to you at no charge. I only ask you to pay for shipping from Ashland City, Tennessee. Hum eliminators work best when interference causes small differences in ground potential (less than 20 VDC) or long cable runs have induced currents. HEC series units also work well when there are multiple power panels in a building that create differences in ground potential which induce ground loop current flow and 60 Hz hum.