Rotary Switching

If you know anything about Paul Reed Smith (PRS) guitars, you know there are a surprising number of possibilities available through the use of rotary switches.  Further, you can use these for switching combinations within a pickup or between several pickups.  In fact, a rotary switch can consolidate all those toggle switches you probably have at the moment for coil tapping, phase switching, and series-parallel switching.  This page provides some ideas.

About the diagrams
Switching within a pickup

The use of a 6-position, 4-pole rotary switch gives you all the combinations possible within a humbucker:

1. Humbucker - Series - In Phase
2. Single Coil - In Phase*
3. Humbucker - Parallel - In Phase
4. Humbucker - Series - Out of Phase
5. Single Coil - Out of Phase*
6. Humbucker - Parallel - Out of Phase
* This configuration is for the neck-most coil.
For the neck pickup

At left is a diagram of the connections to achieve the configuration described above. 

Connect the common lug on the rotary switch as follows:

  • Pole 1 = The "out" wire on a pickup (not the ground)
  • Pole 2 = The other wire on the coil on Pole 1
  • Pole 3 = The wire that would connect to wire on 2 normally
  • Pole 4 = The wire that normally runs to ground

Note: Some folks have gotten confused about what I mean above with Pole 3 being "The wire that would connect to wire on 2 normally."  To clarify, in a standard humbucker, wires two and three are connected in series.  We're going to recombine them using the switch (in some combinations anyway), so they aren't connected together directly anymore.  You have four wires on a humbucker and four poles on the switch to connect them across.  It's that simple.

For the bridge pickup

Now, if you apply this mod to a bridge position pickup, you will probably want to tap the opposite coil so that the bridge-most coil is still hot.  In that case, use this diagram.  Note that all the wiring is the same for the humbucking positions; only positions 2 and 5 have been modified.

Switching between two humbuckers

This configuration also requires a 6-position, 4-pole rotary switch and allows you to achieve pickup switching with combinations in series and parallel with them in or out of phase with one another.

1. Neck only
2. Neck/Bridge in parallel
3. Bridge only
4. Neck/Bridge in series
5. Neck/Bridge in parallel (out of phase)
6. Neck/Bridge in series (out of phase)
(Note that the first three selections are the options on a standard 3-position switch, so they are grouped here for convenience.  However, in practice, I think it makes more sense to put the Bridge-only option last so that the first and last are still the first and last.  See, for example, my red Axis copy.)
Connect the common lug on the rotary switch as follows:
  • Pole 1 = The "out" wire on the neck pickup (not the ground)
  • Pole 2 = The other ground wire on the neck pickup
  • Pole 3 = The "out" wire on the bridge pickup (not the ground)
  • Pole 4 = The other ground wire on the bridge pickup

Rotary switch FAQ
Q: Which one is the common?
A: The common lugs usually stand out.  If they're on the bottom, they're the odd ones out.  If they're on the side, they're usually a little longer than the others (even if they're in the center of the other lugs on that pole).  Use a multimeter and map it out for yourself with a continuity test.

Q: Which row of lugs is Pole #1?
A: Doesn't matter.  It's whichever one you want it to be.  Just decide a group of lugs is Pole #1, #2, and so on, and be consistent.  This of them as the "red pole" and the "green pole" if that helps.  There's no order implicit in their placement the way there is with the throws (i.e., positions).

Q: Can you draw these schematics for me in 3D?
A: No.

Q: I want to make a rotary switch that combines the pickups like blah blah blah.  Is that possible?
A: I'm not going to say "no" because maybe I've just never figured it out.  If I say yes, you're still going to have to work it out for yourself; I won't do it for you.  Just experiment and see what you come up with.

A Magical Idea
If you have a guitar with two humbuckers, run each through the first configuration above, then run the output of each to another rotary as described in the second configuration described above.  This will give you scores of different combinations, yet will still be manageable enough to navigate!  See a mock-up of this mod and additional elaboration on this page.

Some final notes on rotary switches
In spite of the name, rotary switches do not have to be "round."  They come in a variety of combinations and configurations.  For example, the 5-way pickup selector on a Fender Strat is a 5-position, 2-pole switch.  There are a number of other blade switches out there such as the Megaswitch series (available from Stewart-MacDonald) which mimic other more exotic combinations including the PRS switching configuration.

Also, Yamaha makes a super 4-pole, 5-position switch (that's 24 lugs all total once you factor in the commons) which comes with example wiring configurations.  Unfortunately, this too is a blade-type switch. (It is also available from Stewart-MacDonald.)

I did find one place, Guitar Electronics, that carries a true rotary 4-pole, 5-position switch just like the PRS (they include the diagrams to accomplish the wiring scheme as well).  In reality, PRS has recently stopped using this kind of switch and moved over to a printed circuit board switch that accomplishes the same thing.

Copyright Alexplorer.