# Seymour Duncan active/passive preamp bypass explained

Canonical page: https://guitarwiring.app/wiring-guides/seymour-duncan/active-passive-switching

Choose between the pickup signal and the preamp output. See what the switch actually bypasses.

Applies to: A pickup or blend output feeding a separate onboard preamp. This cannot make an inherently active pickup operate without power.

## Two routes to the volume control

A preamp is a powered circuit that processes the pickup signal. The switch selects either its output or the signal before it. The preamp input can stay connected while its output is bypassed.

Only one column of switch contacts is used. A suitable SPDT on/on provides that column; a DPDT or push/pull can use one of its two columns.



## Three connections to identify





Contact in source orientation | Connect to
--- | ---
Upper | Preamp output
Middle | Volume control input
Lower | Pickup or blend output

## Why the pot value matters

A pot is the turning volume or tone control. Its resistance loads the pickup signal. A value chosen for a preamp output may load the raw pickup much more heavily.

The source mentions 10–100 kΩ controls in active systems and suggests 100–250 kΩ for this modification. Treat that as the sheet’s starting point, not a universal recommendation. Check the actual devices in both modes.



## Bypass is not a battery switch

No battery-disconnect wiring is shown. A bypassed preamp may still consume power. Follow its supply and jack-switching instructions separately. Shared ground connections are still needed even though this sheet concentrates on the signal selector.



Sources: WD_Act_Pass_switch, WD_Act_Pass_switch (1). https://www.seymourduncan.com/resources/pickup/wiring-diagrams

Independent explanation by Tinkercaster; not endorsed by Seymour Duncan.