When Fender introduced their S1 pickup‑switching system, many Strat players realised that there was potential for more tones to be had from their single coil pickups than they'd been used to with the conventional five‑way pickup selector. This five‑way switch provides single pickup selection plus parallel pairs (neck/middle and middle/bridge), but if you wire the pickups in series you get a very different sound more akin to a fat‑sounding humbucker.
Most series/parallel switching systems are quite complex, and they may require unwanted visual modifications to the guitar. However, there's a simple system that you can install yourself that gives you three additional sounds, and if you swap out one of the tone pots for a pull‑switch, the guitar looks the same as it did before you did the modification. Furthermore, the mod can easily be reversed, simply by refitting the existing tone pot and moving a few wires.
I can't make any claim to have invented this particular mod — it has been around for a long time now — but it's worth explaining because it can be applied to any guitar with a Strat‑type pickup configuration, and also works well on two‑pickup guitars such as Telecasters. In theory, you could also do it on a guitar with humbuckers, although there'd be no real tonal advantage. My description is based on modifying a Fender or Squier Strat or other guitar with the same pickup and five‑way switching configuration.
With the switch‑pot pushed in, the guitar works exactly as standard. With the switch pulled out, the bridge and bridge/middle pickup positions still work as standard, but in the other three positions you get new tones. With the five‑way switch in the centre position, you get the bridge and middle pickups in series, which gives a very warm humbucking sound that works well with overdrive. In the neck/middle position, the neck and middle pickups are wired in parallel in the usual way but then placed in series with the bridge pickup, yielding a nice humbucker‑meets‑Strat tonality. With the five‑way switch in the neck position, you get the neck and bridge pickups in series for yet another humbucker sound.
To do the mod, you need a pot with a pull‑switch of the two‑pole, two‑way type. You only need to wire one half of the switch, though, as this mod requires only a single-pole changeover switch. The switched pots I use have a small switch mounted on the back with six pins, and are available from numerous suppliers such as All Parts (www.allparts.com) and Axes R Us (www.axesrus.com). You need to check that the knob fits fairly tightly on the splined shaft so that it doesn't come off in your hand when you pull it to activate the switch, and you need to be able to do basic soldering. The procedure is as follows.
1. First, remove the connections from either tone pot, making a note of where they came from. Remove the pot, replace with the switched pot (usually a 500KΩ A-taper type) and then reconnect the wiring just as it was on the original pot. I usually choose the tone pot furthest from the volume control because it's easier to locate and pull than the middle knob.
2. Next, connect the switch contact furthest from the pot to ground by adding a wire leading to the case of the volume pot.
3. Then disconnect the ground wires for the neck and middle pickup from the back of the volume control, join them together and then extend with a new piece of wire to connect them to the centre pin of the switch. Make sure you insulate the joint. Heat‑shrink sleeving, available from general electronics suppliers such as Maplin, makes this easy: you can shrink it by touching it with the side of your soldering iron.
4. Finally, add a new wire joining the hot side of the bridge pickup (I pick this up on the five‑way switch) to the pull-switch terminal closest to the pot.
Now, all that you have to do is carry out a visual inspection to check for bad joints or shorts, before reassembling the guitar. You can check correct operation before fitting the strings by tapping the pickups gently with a small screwdriver as you change switch positions, to ensure that the correct ones are active. Then simply fit some new strings and you're done. Paul White