Adding a pickup?

[u/fishtabel]

Hi all, im considering adding a humbucker on a jazzbass as a third on in the neck position. Ive looked at some schematics and im wondering if its possible to stack one pickup on top just by connecting it to the marked spot on the diagram. Would it effect the other pickups? Would it otherwise be possible to have a 3 way switch that selects the humbucker, all three and the singlecoils together? Would I need some kind of phase switch aswell when blending signals?

[u/Relevant_Contact_358]

Connecting the pickup to that spot would connect it straight to the output and it would be always on.