Pickups In/Out of Phase

Whether 2 coils are wired in series or parallel affects both tone and output.  The animations below suggest a 2-coil humbucking pickup, but these principals also apply to two single-coil pickups.

Animation 1 shows current flowing through 2 coils wired in series.  Notice that current must flow through one coil before it flows through the second.  This wiring, common in standard humbucking pickups, increases output and decreases treble response.

Animation 2 shows current flowing through 2 coils simultaneously.  These coils are wired in parallel.  Parallel wiring retains much of each coils' "single coil" tone, but has less output than series wiring.  In the case of a humbucking pickup, this parallel wiring is still noise-free or "humbucking".  Parallel wiring is common for guitars with single coil pickups when more than one pickup is active.