# Seymour Duncan phase reversal explained

Canonical page: https://guitarwiring.app/wiring-guides/seymour-duncan/phase-reversal

See what swapping two pickup wires changes when you play two pickups together.

Applies to: The conventional passive four-conductor humbucker arrangement in the source. Single-coil baseplates, covers and combined modifications need their own wiring instructions.

## A relationship between two pickups

The source specifies using the phase-reversal modification with two pickups together. The switch reverses one pickup’s electrical polarity relative to the other. Test the combined pickup setting when checking this modification.



## Separate the coil return from the shield

In the standard humbucker arrangement, red and white remain the insulated series link. The reversing switch exchanges the black and green coil leads between the signal and ground destinations. The bare shield stays on ground; it does not become a signal wire.



## Use the drawn contact arrangement

The source drawing shows six contacts and crossed jumpers. Its adjacent switch label lists several alternatives, including SPDT. That label is ambiguous: a three-terminal SPDT does not reproduce the six-contact reversing circuit. Use the appropriate DPDT contact arrangement and check the exact switch documentation.

The drawing is a modification block. Its output still needs to connect to the correct point in your guitar’s selector or control circuit; it is not a complete harness.



## Check the combined setting

Verify the switch connections with a meter before connecting the guitar. Confirm that the shield remains grounded in both positions, then test the pickup alone and together with the other pickup. If the circuit also splits coils or changes series/parallel wiring, use a diagram that includes those controls together.



Sources: WD_H_phase. https://www.seymourduncan.com/resources/pickup/wiring-diagrams

Independent explanation by Tinkercaster; not endorsed by Seymour Duncan.