#1
So I have this two humbucker guitar with two DiMarzios installed, and a coil tap wiring. Today I played it through a cranked valve amp and noticed an almost huge volume drop when engaging the coil tap. Is this normal?

I didn't noticed this before (and felt like a noob) but what actually happens is this:


I thought the coils that got "turned off" were the slug ones, not the adjustable screw ones. I don't know why, it made sense to me. While at it, I experimented rotating the neck pickup (making the adjustable screws face towards the bridge) and noticed the volume drop decreased and I don't know if this is psychological but I kind of liked the tone better this way.

Aesthetically I prefer the screws on the neck pickup facing the fretboard but I guess I could live with the screw coils facing each other... Is there a reason why the slug pickup is the one active during coil tap? Is the position of the slug coil the correct one? Could I wire the pickups so that the slug coil gets turned off? Is there anything I'm not considering? I'm I just too ignorant?

Help me UG you're my only hope.
#3
A volume drop is unavoidable. You're splitting (splitting, not 'tapping') the pickup in half, so the output also comes down to just about half. It does depend on the pickup—some pickups will drop to less than half output and some others stay above half output when split—but either way, half the coils means half the power.

As for position and which coil you split to, it's entirely personal preference. There is no standard.
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#4
I'd imagine that it would be more beneficial to have the adjustable coils active when split. If you've ever looked at a single coil, usually they have staggered pole pieces to make up for the radius of the bridge and volume of the strings. If you adjust your pole pieces like that, it may sound better(but I've never tried it since I don't bother with coil splits).
#5
^ It doesn't really make much difference. With a normal Fender-style single coil, the pole pieces are staggered to match the string/fretboard radius because those poles are the magnets of the pickup. With a humbucker the magnet is one big bar at the bottom and the pole pieces—screw or otherwise—are just there to extend the magnetic field a little bit. Raising them or using different types does change the tone a little bit but it's not like Fender singles where having a pole piece too far or low from the string means you won't hear that string.
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