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RE: Okay - that's solved... Thanks all!

Posted by Sherwood Forest (A) on November 24, 2014 at 11:50:43

In Reply to: Okay - that's solved... Thanks all! posted by Dingojazz on November 23, 2014 at 09:54:01:

Ok, so you're almost there. If the chassis wire solved the problem, then the issue is ground potential difference between the two units, which without the ground wire, causes the ground current to traverse the signal wire connecting the two units, thus making it amplified and audible.

This could easily point to a problem with the power supply of either unit, if there is significant ground current available. I'd do a safety check on the MkIIIs, make sure that there is no dangerous voltage present just to be safe.

Otherwise, it seems to indicate that on one of those units, chassis ground is not tied to signal ground. This could be either a fault, or be by design. It could also be that the shield/ground on your RCA connectors is no good.

So knowing that the ground wire solves it is really only part of the picture. It may wind up being the actual solution, but in this case I would want to know why there is such a potential difference between the two units, and I'd also want to know just how much ground current we're talking about here. This could be a symptom letting you know that you have a condition that might give rise to an electric shock if you were to say, touch the chassis and with the other hand, a grounded metal object. You don't want to find that out the hard way.

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Kimber Kable

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