Different Masters - Different Phases?

[TimK]

I recently bought a sealed copy of My Fair Lady 1976 SQ for decoding thru Audition. When I examined the disk, something about it seemed different. I pulled out my old copy and discovered it was a completely different master pressing. It’s most obvious on side 2, where the lead out groove is at least ¾ of an inch wider than the old pressing. I can’t say I noticed a difference upon listening other than the new copy was sharper and cleaner as expected (had the old copy for 35 years).

I thought I’d do a quick, side by side comparison in Audition. Maybe the old pressing is slightly louder? Then I lined up the waves. Each of the two channels was the mirror image of each other. I’m not an engineer, but I think each channel is 180 degrees out of phase from the old pressing. How will this affect decoding?

I will try to attach pics.

 

[Disclord]

It's not out of phase, the polarity has been reversed on both channels - the decoding won't be affected because it affects both channels equally. If it was out of phase (a single-channel polarity difference) then all center front vocals would come from Center Back. But looking at the waveforms, it's just a polarity inversion of both channels - i.e. absolute phase. Again, it won't affect the SQ decoding. When the 2nd copy was mastered they must have sent the Left and Right channels through an amp or something that inverts polarity - many amps and processors do, and some have switches to invert or not.

 

[TimK]

Thanks for the info. I was just surprised.