Inverting and or non inverting amp?

Tbg...Tube gain stages invert polarity, but a "cathode follower" (unity gain) which is usually included to provide low output impedance, does not. So your rule should be to count the gain stages.

Yarvis...most test discs deal with "relative polarity" as you call it. This relates to the two channels being in phase with each other, and the out of phase condition is very easy to hear. Absolute polarity, where the two channels are in phase with each other but may both be inverted is much much harder to detect and sometimes impossible. Besides, as Elgordo says, who knows which way is correct?

That's not what elgordo said. Try an old Mercury or maybe a Nat King Cole on Capital and the difference is very apparent.

Elgordo...Sorry if I misunderstood you. I thought you were just pointing out that absolute phase is not maintained in recordings. I'm told that different recordings are different, different cuts on a given recording, and even different tracks in a mixdown. I find the effect hard to detect, and even if I could I don't think I could throw the switch fast enough to keep up with all the confusion!