In Reply to: do "bottle heads" use 3 wire power cords? posted by Sam P. on March 01, 2003 at 14:21:30:
Well, you're right that it might be - At least, that there may be a ground loop. I think I'd want earth ground connected to the chassis, but if there was another point that earth ground was connected to signal ground, then I'd want to isolate earth and chassis ground at all other points. I tend to prefer having the connection made at the point where most current is drawn in a system.You want a single point ground, and with all other grounds connected to it. It is a common problem to have the signal grounds connected to the chassis ground, but then to have chassis ground connected to two different earth points, creating a ground loop. This is why the cable for cable television is a common source of noise. Isolate the grounds by connecting through a transformer and the problem is solved.
There are a lot of other things that can cause ground loops, and there are other causes of hum than ground problems too. They're all irritating and difficult to find sometimes.
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