Chasing 60 hz hum

If you have to use cheaters to get rid of hum, then the problem is that the equipment itself is incorrectly wired.

The problem is that the chassis ground and the circuit ground are the same thing, which means the equipment is wired with a ground loop.

IMO, you should send the equipment back to Mac and have them fix it, as other than using ground cheaters, or breaking ground pins off of the AC cords (neither of which is recommended) there will be nothing else that is effective.

Resist the temptation to install an external ground outside the house or other such nonsense- you don't need it! That will simply add to the ground loop problem, which can really only be solved by having the equipment itself wired correctly.

Ralph, isn't that very commonly done intentionally, notwithstanding the fact that it creates the ground loop issue you are describing? And if so, wouldn't a fix (a)be likely to be hard to implement, and (b)be likely to degrade the integrity of the internal grounding scheme that was intended in the design, thereby affecting sonics?

Al, if something like that is done with intention, it can only be out of ignorance, like the kind that existed (and was excusable) 40 years ago. Nowadays you can't get away with it!

On top of that, it **compromises** the sound rather than improving it. Another way of looking at that is that audio components really don't like to be grounded on account of noise in the AC ground and also because of ground loops. If, OTOH, the ground *floats* at AC ground potential, the noise issue is gone and so is the ground loop issue.

Years ago I was of the opinion that a preamp is the place where the chassis and circuit ground being the same was acceptable (this is the way most pro-audio systems are done, although instead of the preamp we are talking about the mixer), but have come to realize that if some other part of the system has incompetent grounding, then the preamp is unfairly implicated. On top of that, if proper grounding technique is observed, you will notice right away that the noise floor is improved (for example, less hiss in a phono circuit) and of course there will be no need for exotic and possibly dangerous external grounding schemes.