Phase Inversion in Preamplifer?

If a system is out of phase you are more likely to hear differences at the frequency extremes, not in the center midrange like vocals. Affects the bass the most in my experience.

I would think having the right channel out the left and vise-versa would ruin the focus/image. Assuming the singer is in the center....
The voice would normally be to the left of the right channel microphones and to the right of the left channel microphone.
Switching the channels puts the sound of the voice on the outside of both channels instead of in the center.

When both speakers are not wired in phase this will of course effect the sound, more noticeably the bass. But if all minus & plus connections between your amp & speakers are correct, and you insert a phase inverting preamp, at this point it will take a very good ear to hear the differences because some recordings are phase inverted (as mentioned above). Personally I would not be too worried over a phase inverting preamp & making corrections. I was told that in order to manufacture a phase correct preamp it will require additional sound degrading circuitry.

Then a test CD that uses a voice to do phase testing seems to be flawed. Something like the Rives CD where piano and bass are used would be more accurate. Correct? On that CD the bass was fine in both tests. However, I think Larryi may still be on to something with the piano, and I'm going to revisit that.

Clio09, a test CD to make phase corrections is a very good investment. If there are no other components in your system inverting phase other than the preamp than reversing polarity on both of your speakers will correct this. I am just saying it is difficult to hear the difference if this is the case. Good deal.

If your system is phase correct, playing music recorded out of phase will not change the phase of your system. If not a mistake, they may have recorded it out of phase to create the sound they wanted when you play it back, that is all. Grooves on an LP or digital code on a plastic CD cannot invert the electrical signal going through your system or add a gain stage to your preamp. You are playing the sound of something out of phase on a system in phase, that is all.

If your CD player has a polarity switch, not sure if it really corrects it or just makes it something else. I have such a CD player and that owners manual says it reverses polarity, NOT to be confused with inverting the phase.

A way to have fun with phase is to play the same signal through both speakers (use bookshelf speakers). Reverse the speaker wires on only one speaker. Now place the two speakers together face to face. It won't be a perfect seal, but if perfect the sound volume would go away (or in your case it would be greatly reduced). This is because the two speakers are playing the same sound 180 degrees out of phase with each other. They will cancel each other out creating silence.

This is similar to the experiments they do to try to make luxury automobiles quieter. They play the frequencies of road noise out of phase to cancel out the actual road noise, making it quieter inside the automobile.