lewm
Playing a mono LP with one channel out of phase will tell you more about channel balance, as it pertains to the electronics downstream from the cartridge, than about azimuth, would it not?No, not at all. You can easily measure the channel balance of each component downstream from the phono cartridge, then factor that into the result of measuring the cartridge channel balance through the same electronics.
How do you define "correct azimuth", with respect to the placement of the stylus in the groove of a stereo LP ...In this instance, azimuth is correct when the stylus is located with perfect symmetry in the groove. As others have noted, there can be slight misalignment of the cartridge coils, so aligning the stylus alone may not produce optimum result.
Seems like with a mono LP ... The exact same signal is then fed to two channels in a stereo system. Then when you reverse the phase of one channel, you would still have signal out of that speaker ... To some degree the two would acoustically cancel, but not nearly perfectly, because phase is affected by room reflections ...You're correct, of course - that's why you don't use speakers when using a mono LP and out-of-phase channel to check azimuth. Use a meter instead.