DC Offset does not cause the AC Ground Loop problem, it is *affected* by it, though.

Ground Loop is two or more paths to AC Ground Potential that are of different resistances. Thus the "loop".

Assuming good shielded cables, constant buzz in the audio chain is almost always AC Ground Loop problem. It is a higher timbre or buzz than that which is caused by an unshielded or broken cable. Listen for a bit of "sizzle" as one clue.

The AC Ground Loop -- and what causes it -- is unfortunately very poorly understood in many circles.


--Mac