What is a ground loop? How can I eliminate the hum and buzz caused by a ground loop?
Please refer to these links:
Also, read the excellent article by Bill Whitlock attached as a PDF file below.
If the hum/buzz occurs when two active audio devices are connected, and:
1) each device is AC powered,
2) the devices are connected from an XLR balanced output to a XLR balanced input.
Trying "floating the ground" on the interconnecting XLR cable. Open the male XLR connector, then disconnect the cable shield from XLR pin 1 and from the XLR connector ground lug. Insulate the disconnected shield so it cannot short to the other male XLR pins. As the cable shield does not carry the audio signal, it does not need to connected to ground at both ends of the XLR cable. Note: making this modification makes this cable unsuitable for use with a wired microphone, like a Shure SM58.