There's some mystery regarding phase reversal. The phase is not something that your ears can detect, in and of itself. What they hear is a channel reversing it's stereo phase, and they know something changed, but not what. They'll do it for the chorus of a pop tune. Dimarzio actually shows you a diagram on their website on how to wire a phase switch for a dual hum-bucking guitar set-up. It's not something you would need as a beginner. It dulls off the magnetism somewhat, which changes the feel. I have an EMG x2 P-90 pick-ups, with the neck pick-up screwed on upside-down, and a high gauge string. You have to pick relentlessly to get a nice action out of it, which was my preference after switching from bass to guitar.A phase switch would give you two sensitivity settings for your pick-ups. 1) Normal mode 2) Drunk mode. It sounds like I'm kidding, but I am not.