Hey, now that you've walked me through it, it's making sense to me. Thank you.
Now of course, my S-100 has a phase switch and I just can't seem to get a grip on that thing.
Phase is actually a cool thing. I have an article coming on that re: pickups, but check this out.
This is the output from my oscilloscope. The yellow line is signal one, and the blue line is signal 2. There are two signals and they are in phase. In phase means that the humps and valleys in the signal are lined up at the exact same place. The purple line is the two signals added together. When two signals are in phase and added together the signal is doubled which is why the humps and valleys are larger in the purple signal.
Now consider the same signal but 180 degrees out of phase. What that means is that where there's a hump on signal A, there will be a valley on signal B. It looks like this. If you look, they are completely opposite signals. The purple line is the two signals added together, only this time instead of there being a doubling of the signal, the signals each cancel each other out. This is the fundamental way that a humbucker works and the way that noise-cancelling headphones work - by inverting and cancelling unwanted signals.
So what happens when you use the phase switch in your guitar? Imagine in the images above that the yellow line is the neck pickup and the blue line is the bridge. When you flick the phase switch, you reverse the phase of the bridge pickup (at least on a Guild) which makes the blue line flip over - it inverts the phase. So why doesn't the sound go away completely? Good question!
The two pickups never have exactly the same signal for a variety of reasons, but they are close - close enough that reversing the phase on one of them makes the end result sound thin - like some of the signal has been sort of... canceled out.
Additionally, it's a bit more complicated than this because reversing the magnetic polarity is one way to reverse phase while reversing the coil orientation is another and they can have different effects. Additionally a pickup does not make pretty pure sine waves like the ones shown not to mention frequency response and more math than anyone wants to read, but in a nutshell that's what's happening.
If you listen to any of my review sound recordings where the guitar has a phase switch, you can hear how thin and tinny the sound gets. You may also notice a lack of volume.
It's easy - it's physics!