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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.
Source and interpretation
Original explanation by Tinkercaster, based on these Seymour Duncan sheets: WD_Act_Pass_switch, WD_Act_Pass_switch (1). 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.