A safer way might be this gound loop isolator from Radio Shack. I have two that work great. http://www.radioshack.com/search/index.jsp?kwCatId=&kw=loop%20isolator&origkw=loop%20isolator&sr=1
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pa4X 76 ,SX900, Hammond SK1, Ketron SD40,Ketron Event X Centerpoint Space Station, Bose compact