help with absolute phase

In case this is not clear, you want to reverse the plus and minus speaker cable leads at BOTH speakers OR for both channels of speaker cables at the amplifier. Red to black and black to red. Inverted phase is not the same as AC polarity, so this is independent of your AC power. And it is not the same as out-of-phase, which is much more audible, and which happens when the plus and minus are inverted on one channel only. If your preamp inverts, as your does, I am told that it makes sense to do this procedure even though, as Elgordo says, you will still be "off" for about half of your CDs. What the audio world needs is more preamps and processors with remote control phase reversal.

Onhwy61's post was excellent. My recommendation that you make the change was no more than regurgitating audiophile best practices. But truth to tell, I don't hear a meaningful difference myself. I have known some who are highly sensitive to it, however.