How Do You "Stack" a Single Coil Pickup?

[CheshireCatFun]

Bruce and Walter answered the question just fine.

So it would appear.

Speaking of which, have you ever worked with stacked designs before, and, if so, what is your experience with them?

C.

 

[totalnoob]

This is the best image I could find that explains the concept.

View attachment 2122508

Basically, the top coil is magnetized using standard magnets. The bottom coil has only ferrite cores which aren't magnetized, but are used to bump up the inductance that is mostly responsible for noise collection. The magnetic field doesn't permeate the bottom coil due to a metallic plate between the two coils, and the fact the bottom coil is further away from the strings ensures it collects most of the noise and nearly none of the signal. After it's connected in counter-phase to the top coil, it helps reject the hum both coils are sensing. Note that it can be wired in series or parallel to the top coil - in both cases it will hum-cancel equally well, however, the tone will change, for better or worse, because you still have two coils connected.

This is 1000% correct! I was reading this thread a bit dismayed by some non-scientific statements, and then this absolute GEM comes up! Thank you, Stealth!

 

[totalnoob]

I've heard this explanation a lot but it does not work magnetically. If the magnets go all the way through both coils then both coils are magnetically polarized the same way and the string signals generated by the two coils, like the external hum signals they both pick up, will be out of phase because the coils are wound oppositely.

Exactly! Having the magnets go through both coils in this way will make for a terribly poor pickup indeed.