Viridian, I can't speak for all preamps but on our preamps the phase switch is very simple, as our preamps are internally balanced. So to do the phase reversal requires no circuitry other than the switch itself.
I have found that the switch does not have much use unless you are listening to a fairly pure recording- one that is done with a minimum of microphones (hopefully only 2 and if there is a third it is the center channel). Then the difference can be quite noticeable. I've not found the speakers to play a huge role in this.
I have found that the switch does not have much use unless you are listening to a fairly pure recording- one that is done with a minimum of microphones (hopefully only 2 and if there is a third it is the center channel). Then the difference can be quite noticeable. I've not found the speakers to play a huge role in this.