> Hi Alan, >=20 > What is the specific situation at mains frequency that you would call a > "ground loop"? >=20 > Sean The hum you get in a PA system when connecting multiple items together, and= then breaking the ground at one point removes the hum. --=20 Scanned by iCritical. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .