Tinkercaster
The wiring reference

Seymour Duncan phase reversal explained

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

Start here · What you are looking at

One pickup. Two coils inside.

A pickup sits under your strings. A magnet and coils of fine copper wire turn string movement into an electrical signal for your amp. This type is called a humbucker: its two coils work together to reduce electrical hum.

1 Screws you can adjust
2 Smooth metal posts
A typical humbucker with its cover removed, viewed from the strings.

1 The screw coil

The row with screw heads. There is a coil of fine wire underneath this half of the pickup.

2 The smooth-post coil

The other row has smooth metal posts, called slugs. “Slug coil” simply means the coil around that row.

What is a coil?

Lots of turns of thin copper wire, with an end at each side. Two coils give us four coloured wire ends to connect.

Why do some diagrams say “north” and “south”?

Those names describe magnetic polarity, not the top and bottom of the guitar. On the conventional Seymour Duncan humbucker shown here, north refers to the smooth-post coil and south to the screw coil. Other designs can differ. “Inner” and “outer” depend on which way the pickup is installed.

Background: Seymour Duncan’s anatomy of a humbucker.

See what changes

Swap two wires on one pickup

Usual connections

Black → signal output

Green → ground

Bare → ground, always

The pickup sends its signal to the controls. Red and white stay joined and insulated in both versions.

Swapped connections

Black → ground

Green → signal output

Bare → ground, always

A switch swaps black and green on this pickup. Listen with another pickup selected too: parts of their signals now oppose each other, often making a thinner sound.

This explains what the circuit does. Use the complete wiring diagram for the exact solder connections.

When you are ready to wire it

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.

Source and interpretation

Original explanation by Tinkercaster, based on these Seymour Duncan sheets: WD_H_phase. The guide describes the stated configuration; it does not establish compatibility with every pickup or switch.

Seymour Duncan’s wiring diagram library ↗

Not affiliated with or endorsed by Seymour Duncan. Refer to your exact component’s instructions when a detail differs.

See it in a complete diagram

Put it in a complete circuit

Use a complete wiring diagram to see how the pickup, controls and output connect. Our public diagrams are free to view and explore.

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Understand this wiring

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