ARC REF 3, Nagra PSA, & Phase Inversion


Last night, while I was auditioning a Nagra PSA for my primary system, at the suggestion of a friend, I inverted the phase on the REF 3. The sonic effects were remarkable. The speakers disappeared further. The sound stage became much more defined and deeper; it extended a little more forward, quite a bit more backward, and even a little wider. Imaging, which had always been quite good, was also markedly improved. And the overall musical presentation was more relaxed (for lack of a better word) and musical (to my ears). I was really shocked but also quite pleased with the changes I heard!

Can someone explain what exactly goes on with phase inversion and how it can cause the changes I heard (and perhaps other changes that occurred and I did not recognize them)?

Thanks in advance!
4musica44107
Microstrip:

For the evaluation I was doing, I was using the balanced output. I am going to talk to my friend who suggested the inversion and get his explanation, then share it in a subsequent response for this thread.
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."
Dan31:

I now own that Nagra PSA! It is by far the best SS stereo amp I have heard at anything near its price point. It presents quite a different sonic landscape than my Luxman MQ-88, but I like the Luxman just as much so I am keeping both amps. This probably qualifies as conspicuous consumption but I don't care!

The Nagra is fast, accurate, musical, and seems to have more power than its rating. The music flows effortlessly. The highs are definitely improved over what I hear with the Luxman, and the bass response is so good that I have not yet bothered to tie in the REL B-2 that I always use with the Luxman. And I probably won't.

My speakers in my main system are the Verity Fidelio Encores. It is perhaps worth pointing out that when Verity shows their speakers at shows, they typically use Nagra amps. From what I have heard so far, I understand why they do!
4musica44107,
May I ask what other preamps have you used with the Nagra PSA apart from the ARC Ref 3? Have you tried a passive pre with the PSA? What are you thoughts on other preamps used with the Nagra PSA? Thanks in advance.