Preamp inverts signal.

What is interesting and a little mysterious in George's very thorough explanation of absolute polarity is that entire CD LABEL repertoire are inverted polarity which seems to rule out randomness of CDs being inverted polarity. Mapleshade is an exception but on George's list the big boys like Mercury Living Presence and RCA Living Stereo CDs and Deutsches Gramophon are inverted polarity. So, ensuring one's system is polarity inverting might actually be a very good idea if his taste runs toward classical music. My only nagging reservation is that nobody else has confirmed George's list as far as I know, which does show an overwhelmingly high percentage of CDs having inverted polarity. I do find myself much preferring analog versions of RCA Living Stereo recordings including cassettes over the CD version, but it's difficult to say whether the reason fir this preference can be attributed entirely to the difference in absolute polarity, but I'm open to the idea that it might be a lot of the reason.

Phd,  I invert it at the amp side, makes no difference though 

"Sidebar, how can I test my system for polarity? Test track?"

The most reliable way to test the system for absolute polarity is the in phase and out of phase tracks of the XLO Test CD. Of your system is in the correct absolute polarity the Out of Phase track will sound like it is coming at you from all around the room with no specific direction. And conversely the in phase track will sound like it's coming from dead center and be very focused. These effects are much more pronounced with proper speaker set up and after careful attention to room tuning. 

Geoff Kait

Geoffkait 03-20-2016 7:17am EDT
Of your system is in the correct absolute polarity the Out of Phase track will sound like it is coming at you from all around the room with no specific direction. And conversely the in phase track will sound like it’s coming from dead center and be very focused.

The description of "out of phase" in the first sentence is the effect of relative polarity being wrong, not absolute polarity being wrong. In other words, it is the effect of having the output of one speaker out of phase with respect to the output of the other speaker. Which would be the result of having + and - reversed in the connections to one speaker (but not both). The effects of incorrect absolute polarity (having the outputs of both speakers inverted, relative to the polarity that is presumed to have been received by the microphones during the recording session) are vastly more subtle, and may be imperceptible on most of the recordings that have a mix of different polarities for different instruments and singers.

Phd, thanks for the nice words.

Regards,
-- Al