Phase inversion switch.Since I've never used one before I can't say I really know it's effect on the music.Perhaps someone could enlighten me?
The phase invert switch's effect depends on the recording. It can make a big difference (good or bad), or no difference. No difference is usually reserved for over-produced music, though good ones sometimes change from it too, albeit far less often in my experience.
Not sure if the switch effects the speakers' polarity or not. A ton of speakers are wired out of phase due to crossover designs (I think). Reversing the polarity with your speaker wires can make a huge difference - better or worse.
A dealer showed me that trick - reverse positive and negative on both speakers at one end only. When I auditioned the Revel F12 towers, they sounded good, but a little too bass heavy and the soundstage was distant. He reversed the wires, and the bass tightened up (didn't go quite as far down though) and the sounstage came forward. It was almost like a different speaker.
My current speakers are in phase and sound best that way. Since I've heard that demo, I've tried the polarity trick with every pair of speakers. Very rarely did I not hear a difference.
My current DAC has a polarity switch. It benefits music far less often.
