Way back in the day, when the British telephone system was operated by the GPO (General Post Office)...
A woman calls to tell them that her dog is telepathic. The dog knows a couple of seconds before the phone rings, and announces the fact by howling... BEFORE the phone rings!.
She's ignored for a while, but eventually someone drives out to take a look.
It seems that the dog is chained up in the yard -a metal chain of course- to the telephone pole where the service comes in. The ground has lifted-and-linked, and the phone loop is partly returning via ground... and as luck would have it, it's partly returning through the dog chain -and then via the dog- to ground. The phone ring has become a little weaker, and -in those days when the claper used to bounce between two bells- it takes a second or so for the clapper to gain it's full swing and start striking the bells.
So now, every time someone telephones her, the ringing voltage is 'tickling' the dog, who starts to howl, because it's so unpleasant. -A second or so later, the clapper has got enough kinetic energy together to start ringing the bells.
The poor dog had been tormented for months before they worked out how it was happening!
So -with that tale in mind- yes, power issues can go unnoticed and be "fixed" by balanced power, but Measuring line-to-ground voltages on live and Neutral, and checking that there's no secondary Neutral-to-ground links downstream, and no neutral/ground conductor swaps or other stupidities, it's perfectly possible to have "inky, black silence" from wide open gains, without resorting to balanced power.
..And yet people seem to buy into it "because it's balanced and therefore better". I'd be spending that money on something that made me money or that I could enjoy, rather than balancing power.
One thing that balancong power FORCES you to do is ELIMINATE neutral/ground confusions, and that in itself fixes most stuff. -As a result, when facilities have installed and tested balanced power, you'll often find that bypassing the balancing transformer demonstrates very little or often absolutely no increase in noise floor.
And balanced power or no, ground loops are still going to hum.
Keith
