# Seymour Duncan phase switching with coil split or parallel

Canonical page: https://guitarwiring.app/wiring-guides/seymour-duncan/combined-pickup-switching

Two switches interact. See what changes when coil selection and phase reversal share a pickup.

Applies to: The two linked humbucker modification sheets, using conventional Seymour Duncan four-conductor colours.

## Coil split plus phase reversal

In the first sheet, red and white go to the split switch’s middle contact; its upper contact is grounded. Black and green go to the phase switch’s two middle contacts. Bare always goes directly to ground.

When the series link is grounded, changing which outer lead is hot changes the retained coil. These controls do not simply reverse the same isolated coil in every setting.



Split switch | Hot lead | Result from the drawn connections
--- | --- | ---
Link ungrounded | Black | Both coils in series
Link ungrounded | Green | Both coils in series, reversed polarity
Red + white grounded | Black | Smooth-post coil
Red + white grounded | Green | Screw coil

## Series/parallel plus phase reversal

The second sheet first forms the series/parallel circuit, then takes its two output ends to the phase switch. Green reaches that switch as the coil return; do not permanently ground it as in the standalone series/parallel example. Bare stays permanently grounded.

A two-position mode switch gives series and parallel. The matching three-position version adds split. Here the mode circuit selects the retained coil before the phase switch exchanges its output and return.



## Connect the reversing switch

Label the left column L1/L2/L3 and right R1/R2/R3, top to bottom. Connect the pickup circuit’s output ends to L2 and R2. Add jumpers L1–R3 and R1–L3. Take hot from L3 and ground from R3. The crossing jumpers do not join at their crossing.

The source label includes SPDT despite drawing six contacts. Use the drawn DPDT reversing arrangement; a single three-terminal pole cannot do this job.



## Check every combination

Phase reversal is heard relative to another pickup, so test with both selected. Check every combination and confirm the shield stays grounded. These connectivity explanations do not predict exact tone or prove hum cancellation with an arbitrary second pickup.



Sources: WD_H_link_ph_spl, WD_H_link_ph_ssp. https://www.seymourduncan.com/resources/pickup/wiring-diagrams

Independent explanation by Tinkercaster; not endorsed by Seymour Duncan.