Correct Way to Invert Phase

Hi,

My Conrad Johnson preamp is phase inverting.

The CJ manual says to change the phase "...by reversing the positive and negative connections to your speakers (be sure to reverse both channels)..."

Can anyone explain why changing the positive and negative connections between the amp and preamp would not accomplish the same thing?

Just wondering if this could harm the components or is some other science at work here that I do not understand?

Thanks for listening,

Dsper