Its a made up problem that for practical purposes only exists on paper. There is nothing to solve if you live and work in the real world.
With loudspeakers, L and R + and - are kept separate on a standard amp, but if you connect a headphone (with resistors), ground of L and R are united (only three contacts on a TRS plug) and apparently may cause a havoc with the output transformers having a common ground. Distorsion, overheating in the seconadary windings?
This problem does exist on paper, but not in real life.
There are many things that can cause crosstalk in an amplifier.
Under optimally bad conditions the TRS jack or a shared ground *could* cause crosstalk, but conditions really need to be optimally bad - 1ohm speakers or do something so stupid that it can only be considered malicious. It is not a real problem.
More common causes of cross-talk come from poorly designed power supplies or overall amplifier design and layout. These problems dont require much more than a bit of cash, some time, and/or a little more chassis space to solve, but they must be planned for. Planning for them is easy. The problem is that the result is sooooooo subtle (not really) that the average listener will not pick up on them. How should the MFR guarantee that their hard work pays off? Aah! come up with some ******** about something totally unrelated, but very sexy.*
The continuous parroting of this misinformation is kind of sad. At best it is misinformed. At worst it is designed to deliberately misguide the consumer. It is almost always a strawman.
* I am firmly in the camp that there are some inherent advantages to balanced amps (particularly if you avoid global feedback) despite how negative this post may sound. Its just that this particular argument is sooooooo annoying.
Monoblocks do not have better channel separation than 2-ch amps because they separate the ground. They have better channel separation because they separate the power supplies. Unless you use a cheater plug or do some other questionably safe things the grounds are still connected....
Balanced amps do not have better channel separation than SE amps because they have omitted the TRS plugs, they have better channel separation because they have isolated the signal current loops.
Edited by nikongod - 12/26/13 at 3:51pm