My friend who suggested I try the phase inversion explained his rationale this way. He said that most tube preamplifiers do not have a second amplifier stage ( although a few do, according to him) and thus are out of phase with a solid state amplifier. Thus inverting the phase should bring a system's tube preamplifier (in most cases per his clarification above) and SS amplifier into phase. At least that is what I gleaned from his comments. Whether the explanation is "correct" or not, there must be something to this, because when we tried the phase inversion with the SS Nagra PSA, I easily noticed all of the nice sonic improvements I mentioned in my original post for this thread. And this was evident on all of the 10 to 12 recordings we listened to. On the other hand, when I switched to my Luxman tube amp, phase inversion in the same system did not improve the sound, and in some ways it was less "good."