Well just to be clear, phase, polarity, and of course channel assignment are 3 different things. Absolute phase--or inversion of such--is a somewhat subtle thing, and it is not uncommon for equipment to invert it. Plus most recordings do not maintain absolute phase throughout. While many people would prefer to get it right, it will vary from recording to recording. Polarity--between between left and right channels--is wrong when one channel is wired out-of-phase with the other (as in one speaker is hooked up to the amp opposite to the other). That is easiest to hear by putting your preamp in mono--there will be obvious bass cancellation. Getting 2 channels out of phase with each other (polarity reversal of one channel) is terrible and must always be corrected. I am not aware of this happing or being adjustable with any gear. And of course Left-Right channel assignment is self-explanatory.