Mains Out

Inverted inverts absolute phase. Some people can hear the difference. If you are going to bi-amp they both should be connected to outlets that are either inverted or normal. If you use one of each, it would be (more or less) the same as connecting the speakers out of phase- predominately a loss of bass and poor imaging.

Trouble is there are NO standards on recorded music. Even within an album you will find absolute phase differences between tracks.

You may want to test your ability to hear this before calling it an issue.....

Connecting a pair of amps....one driven 'normal' and the other thru 'invert' should NOT be a problem if doing a biamp with stereo amps.. Just swap one pair of speaker leads. For monoblocs? Same deal.

The other solution would perhaps be to make some custom, phase inverting interconnects. I don't know if that's such a good idea, however. Or even if you won't screw something up......ground typically likes to go to hot thru a load.....

The simple solution would be to swap the positive and negative speaker leads on the amp using the inverted inputs. If you invert both the interconnects and the speaker leads the absolute polarity will not change and all will be well.

My Herron pre-amp also has that function. On a few older records, inverted phase makes imaging goes one side, reversing it corrects them. On most new recordings,imaging and tones are more focused and alive with the correct phasing. Very useful, I try it with every record I played.