Mini toggle - neck pickup S1 switching curitosity/tonal difference

[danburne]

Hi
Thought I'd share this...

I have a USA Fullerton S-500. Even when just the neck pickup or the neck and middle are selected with the 5 way, switching the mini toggle (which just engages the neck pickup) changes the tone subtle. I assumed it shouldn't, so I had a dig around as to what's going on. It's actually quite a handy additional tonal variation!

Here's what GPT had to say about it:

On the G&L S-500, the Expander mini-toggle is a DPDT switch that not only ties in extra pickups but also reroutes the neck pickup’s hot lead through an alternate set of switch lugs. Even when you’re in “neck only” on the five-way, flipping the Expander shifts the neck pickup’s connection from one pole of that DPDT to the other pole—changing its wiring path into the volume/tone stack. That small change in path (with different trace lengths, contact resistance, and how the pickup interacts with the PTB network) subtly alters impedance and frequency response, so you hear a perceivable but small tonal shift.

1. How the Expander Switch Is Wired
DPDT action: One pole ties neck & bridge in positions 1 & 5 (the “Tele” tone), and positions 2 & 4 become all-three pickups
guitarsbyleo.com
.

Second pole: Rather than sitting idle in neck/bridge positions, the second pole swaps the neck pickup’s hot lead between two different sets of five-way switch lugs
guitarsbyleo.com
. Those alternate lugs feed the rest of the circuit (volume, PTB) slightly differently.

2. Why a Different Wiring Path Changes Tone
Impedance and Resistance

Different lug traces and contact resistances—even a few ohms—alter the load on the pickup, shifting its resonant peak
glguitars.com
.

Interaction with the PTB Stack

The PTB (Passive Treble & Bass) system uses separate caps (0.022 μF treble, 0.0022 μF bass) and pots to sculpt tone
Reddit
Vintage Guitar
.

Though the caps are “always on,” rerouting the pickup’s hot lead means it sees those caps—and the volume pot’s bleed cap—under slightly different wiring nodes, tweaking the cutoff frequencies.

Signal-Path Length

Swapping poles can add or remove a short bit of copper trace or ground reference, subtly altering high-frequency roll-off
GuitarNuts 2
.

3. Designer Intent & Practical Effect
Two “neck” voices: Leo Fender’s Expander gives you pure neck (Expander down) and a shaded neck (Expander up)—a bit more “snap” and midrange presence without dirt pedals
glguitars.com
.

Use cases: Many players leave the Expander on for a slightly tighter, more articulate neck tone in funk or country, switching off for warmer cleans
The Gear Page
.

4. Verifying & Fine-Tuning
Check the schematic: Compare your wiring to G&L’s official S-500 diagram (e.g. on Guitars by Leo) to confirm both poles of the toggle are wired correctly
guitarsbyleo.com
.

Measure resistance: Use a multimeter to see how the pickup’s DC resistance changes with the Expander—you should spot a slight difference.

Swap caps (advanced): If you want to neutralize the change, you could rewire so both toggle positions feed the same lug for the PTB stack—although that sacrifices the shaded-neck option
guitarsbyleo.com
.

In short: The Expander isn’t just an “add-bridge” switch—it’s a DPDT that reroutes the neck pickup’s hot lead through a different pole even in neck-only mode. That routing change alters impedance, interactively tweaks the PTB caps, and shifts frequency response, so you hear a subtle but real tonal difference.