13 is better than 5

This is a modification to increase the number of tonal possibilities in a 3-pickup guitar, beyond what is offered by the standard 5-position "Strat" pickup switch.

I replace the 5-position switch with three 3-position toggle switches, one per pickup.  Each switch has a center-off position.  The other two positions turn on the associated pickup.  The downward position is in-phase, the upward position is out-of-phase.  Thus, every possible combination of pickups and phase is available.

In fact, a number of the combinations are redundant: i.e., they sound exactly the same as another combination.  There are 27 possible combinations, but only 13 useful and distinct tones (plus all-off).

Demonstration of the 13 tones:
https://soundcloud.com/benjamin-ketcham/3-switch-strat-tones

This is effectively the same wiring as Brian May uses on his famous Red Special guitar (except that he uses six 2-position slide switches; I prefer it as the three 3-position toggles).

I'm doing this modification to my new little Squier Mini-Strat.  I originally considered implementing a smaller number of additional tones, not every possibility, through adding some pull-switches to the volume and tone knobs.  Less versatile, but can be done "reversibly", without permanent damage to the guitar.  My method here requires drilling new holes in the pickguard.  I arranged to do this in a "minimal-impact" way, in that the new holes follow the slot of the old 5-way switch.  The toggle switches protrude through these holes and then mount to a brass switch-plate which I am fabricating, and which attaches to the pickguard using the old screw holes for the 5-way switch.  I will save the old switch, and thus one could restore the old functionality, albeit with a somewhat jagged-looking slot for the switch handle; one  would probably want to replace the pickguard.  Good thing this guitar's not vintage!  But I'll never change it back anyway, this wiring is the way to go.

So probably of interest to others, is both the wiring to accomplish this, and how I physically do it so that it looks reasonable.  Do I need to mention this?  Don't undertake a project like this unless you are quite confident in your competence, both to open up your guitar and drill holes into it, and also to make really good solder joints.

The switches are DPDT center-off mini panel-mount toggle switches, which I got from digi-key (.com).  This type of switch is available with several kinds of toggle: rounded, flat, metal, plastic, different lengths, etc.: be sure to look at the alternatives and choose something that will look and feel nice for your guitar.  These little items are pricey, but don't try to cheap-out too much on this.

Here are the 13 "useful" tonal combinations.  Note that I call the pickups "bass", "middle", and "treble".  Many others call them "neck", "middle", and "bridge".  I organize the combinations as shown, mentally, into four different groups:

The dashed line separates the combinations into two major categories, which I call additive and subtractive.  The subtractive sounds have one pickup out-of-phase with the rest; the additive sounds have everything in-phase.

The additive sounds consist of the five standard "Strat" sounds (tones #1 - #5), plus the two combinations you can't get with the 5-way switch alone: treble plus bass (tone #6), and all three (tone #7).  Some of the newer Fender guitars have a pushbutton in the volume knob, which they call the "S1 switch", which allows you to get tones #6 and #7; hence my name for these tones.

The subtractive sounds involve either two or three pickups (flipping the phase on a single pickup makes no audible difference); there are three possible variations for each, so a total of six subtractive settings (tones #8 - #13).

My Squier only has two knobs, but most Strats have three.  I should note that, with three knobs, it is possible to get all these tones without drilling the pickguard, by putting a pull-switch into every knob position.  The logical way would be to put an "S1" type switch with the volume knob (if not already so equipped): this switch turns on the bass pickup, independent of the 5-way switch, thus enabling tones #6 and #7.  For the out-of-phase tones, it's only necessary to be able to flip phase on two of the pickups, not all three, so a phase switch in each of the two tone knobs would do the trick.  As mentioned, I don't have the three knobs needed to do it this way, and I don't mind making permanent mods to my guitars.  Plus, I find the three-switch wiring presented here, to be more intuitive than figuring out how to get the same combinations from a 5-way switch supplemented with pull-knobs.  But if I had a nice vintage Strat, I'd probably think twice.

I thought the all-off setting, #0, might have more hum problems than muting the guitar with the volume knob.  However, at least on this Squier with the amp I'm using, there seems to be a low-enough impedance from the volume pot, that there's no hum in position #0, so maybe my warning about this is needless.