You have a guitar with a given range of tones and you want to get more out of it.
You can achieve quite a bit by redesigning the circuit inside the guitar. It may sound baffling at first but it really isn't that hard.
 
My goal here is to provide you with some ideas and instructions on how to achieve different sounds, by changing the ways your pickups are combined. Diagrams are included, but they are local diagrams, so that you can integrate them in bigger schemes. The only complete scheme you will find here is the current setup of my own guitar. If you can understand it, then I did my job well. I won't venture into talking about replacing components with ones of different performance. That's a whole different chapter.
 
CONTENTS: available pickup combinations, available switch types, basic rules for designing passive guitar circuit, instructions and diagrams, a big example.
 
The options
 
Typically guitars are equipped with two or three pickups that are either humbuckers or single coils, and a 3way or 5way selector switch. Humbuckers and single coils differ in sound properties. How can you get some of the properties of one type of pickup, with a guitar that has the other kind?
The answer is: by modding the circuit to recreate the conditions. It is easier to make a humbucker sound like a single coil, than it is to make a single coil sound like a humbucker.
 
Here are the main options you have:
* Humbucker out of single coils: Connect two coils in series.
* Single coil out of humbucker (coil tap): turn off one of the two coils of which the humbucker consists
* Parallel coils of humbucker
* Out of phase parallel coils of humbucker
* Out of phase pickups: for a hollow tone
 
Single coils typically tend to have a brighter sound with more definition and "bite" and less output than humbuckers. A coil-tapped humbucker acts in a similar way. A humbucker with the coils in parallel also sounds more open but in a different way than the same humbucker coil-tapped, because it picks up sound from a wider area under the strings.
Phase reversion causes frequencies to be cancelled out. Low frequncies are a lot more affected. The closer the out-of-phase coils are to each other, the more similar their signal is, and the thinner their sound will get. Here I will only discuss how to chage the phase between pickups which produces more acceptable results. The concept is the same for reversing the phase inside a humbucker, but the sound is too thin for most people's needs, but indie rock players may find it interesting.
 
 
The switches
 
The typical factory setup of guitars uses selector switches with internal jumper connections (especially the 5way switches). This means that positions 2 and 4 are entirely dependent on their flanking positions 1&3 and 3&5 respectivelly. There are switches that have independent tips instead of jumpers for positions 2 and 4, allowing you some more freedom.
Also, the typical switches have two poles, which means they can switch two independant connections at the same time. There are switches with 4 poles, that can handle four connections at the same time.
Then, there are mini switches (2-pole 2way usually) for toggling and there are push/pull pots which are your regular pots with a built-in mini switch, so that you don't have to drill new holes for the switch.
There are also rotary switches, that look like potensiometers from the outside. Useful if you want a switch to replace a pot you don't use.
 

 
Some basic rules
 
1) Every pickup has two ends: Hot & Ground. Hot goes through the pickup selector switch and then through the volume potensiometer and finally to the tip of the jack. Ground goes directly or indirectly to the universal ground (typically the back of a pot) and then to the coat of the jack.
2) A 4-conductor humbucker can be treated as two individual pickups (1 & 2), each with its own hot and ground (H & G) wires. Typically 1H goes to the selector switch and 2G to the ground. 1G and 2H are either connected with each other or used to alter the pickup's operation mode. Keep it in mind. I'll use it for the examples. Consult your pickup manufacturer for their color code.

3) Make sure you understand the order in which actions must take place. Controls specific for one pickup must be inserted in the circuit before the selector switch. Global controls must be put after the selector switch.
4) Make sure you understand which connections and wires are active every time. Ergonomy often dictates that wires of different origins be soldered together on the same tip of a control, but the truth is that often not both af them are active at the same time. For a wire to be active, a full loop from ground to hot must be formed.
5) Just because you have planned that the signal should go "from A to B, merged with C and then goes to D" it doesn't mean it will happen so. Don't think of wires as directional highways. Think of them as a network. Electricity will travel either way through any wire, as long as doing so completes a loop between any hot and any ground points (the ground side of pickups and controls is usually permanently connected so watch for unpredicted "hot" connections). The most unpredictable shorting is the leaking through the tone controls (unless you use one universal tone control). If using tone controls for individual pickups, make sure they are activated and deactivated along with the pickup they control... The best way to do so is to connect their "hot" end on the same tip of the selector switch as the "hot" end of the respective pickup. Many of my first attempts at designing circuits failed because of this. However, you can use this to your advantage (see "blow switch" example below)
 
 
Finally, the instructions
 
All examples are drawn from my current guitar setup (yes!! I do have all of the following on one guitar!). The concepts described, however, are the same, regardless of the type of pickup and switch you use to make it happen.

My guitar has two humbuckers and one single coil, which I think is an ideal setup for getting the most tones out of one guitar. In addition, the two coils of each humbucker differ in output and tone, adding the bonus option of choosing which side to use for tap.
Ok, enough with the bragging. Let's get to business!
 
To start with, connect the wires 1H to the selector switch and 2G to the ground and forget about them (see basic rule #2), unless you have a phase switch in mind. To alter the pickups' mode you only need the wires 1G and 2H, but you'll need 1H and 2G to change the phase. Wire the selector switch as you would if no mods were to take place, but you can experiment there too. Some pickup modes can be achieved directly with the selector switch, but you'll sacrifice original modes in the process. I prefer adding options. Not replacing them, much less substracting any.
 
Now you need a switch (or more ;P ). I favour the 4-pole switch because it allows me to tweak both humbuckers in a single move, and can accomodate 5 modes. A push/pull pot used in the same way can only offer two modes for one humbucker. The catch is that adding a 5way 4-pole to your existing setup is a radical and irreversible intervention. I'll use a simple mini switch like the one found on push/pull pots for the examples, since it is the less intrusive method.
 
Connect the wires 1G and 2H each to the end-tip of a pole of your switch of choice. Now come the options:
 
mode switch: affects the tone of your humbuckers. These are the common options:
series operation: This is the typical humbucker mode. Find the active tips for the desired switch position and make a jumper connection between 1G and 2H.
parallel operation: Connect the tip from 1G to ground and from 2H to the selector switch, together with 1H. Don't worry about interferance.
single coil operation: Connect the tip from 1G to ground and leave 2H unconnected. Alternativelly, connect the tip from 2H together with 1H on the selector, and leave 1G unconnected.
You don't need to apply the same operation mode(s) to both humbuckers. Find what best suits your needs.


 
pickup phase reversion switch: This is two steps trickier. To achieve this you have to reverse the active hot and ground ends of the pickup. This usually doesn't affect the pickup's sound directly. It becomes apparent only when the pickup is used to gether with another pickup.
The switch must be inserted right before the pickup selector: Whatever wires regarding this pickup would connect to the selector switch, must instead be connected to the end-tip of one pole of the phase switch. Whatever wires regarding this pickup would connect to ground, must instead be connected to the end-tip of the other pole of the phase switch. (Except: the wires coming from tone controls - if you don't use a universal one. If you take the tone wire to the phase switch along with the others, you'll lose functionality of the tone control when you reverse the phase - trace the loop: it will be ground on both sides of the control). The end tips for a push/pull pot are the central pair. Connect the two tips farther away from pot body to the selector and to the ground respectively (as they would if no switch was present). Now make two jumper connections, like an "X" across the phase switch: connect top right with bottom left and top left with bottom right.

 
"blow switch": Using the neck and bridge together, on a three-pickup guitar. This is simple, yet requires thinking a bit out of the box. Create a new wire connection from the neck position of the selector switch to the end-tip of a pole of the "blow" switch. Also connect a wire from the bridge tip of the selector to the end-tip of the other pole of the blow switch. Now make a jumper connection across the poles between the tips nearest to the pot body. This way, when the blow is activated, whenever either of the two pickups (neck or bridge) is active, the other one will be too. The wires here act as a bridge and electricity will flow from the inactive pickup through the bridge to the activated position. Depending on which position the 5way is in, electricity will flow in opposite directions.
Positions 1 & 5 of the 5way selector will cause only neck and bridge to be active, positions 2 & 4 will have all three pickups active and position 3 will have the middle pickup alone.

 
Thinking outside the box
The following diagram shows a 4-pole switch used as a pickup selector, to integrate a phase switch and a coil tap, without the fuss of extra switches.

Notice how 1G & 2H are soldered together for both pickups, turning the bridge pickup (top) to an essentially 2conductor pickup and the neck into a 3 conductor pickup.
Position 1: The top half of the switch connects 1H and 2G to hot and ground respectively, activating the bridge pickup (which is always in series mode).
Position 2: The top half of the switch reverses the phase of the bridge pickup. The bottom half of the pickup activates the neck pickup. You get two pickups in out of phase operation.
Position 3: The bridge pickup is back to normal phase and the neck pickup is still on. Standard two humbucker operation.
Position 4: The bridge pickup is off. The neck pickup is on, but only the first coil is active (single coil operation). The second one has been shorted out by making a ground connection between the two coils.
Position 5: Neck humbucker alone.
 
Now, let's put all that knowledge together!

It's late and I just drew that from memory... It's a complex scheme, so let's hope I did it right. ;P
 
The outlines: This setup uses a universal volume control, 2 tone controls (one for each humbucker), 1 5way simple selector switch, 1 5way 4pole mode switch, 1 phase switch and 1 blow switch.
 
The easy part first: The middle pickup has one end connected to ground and one to the selector.
The bridge humbucker (top): Straightforward application of the instructions: 2G goes to ground, 1H to the selector and 1G & 2H to the big 4-pole mode switch.
The mode switch:
Position 1 selects the inner coils mode for both humbuckers.
Position 2 selects the outter coils for both humbuckers.
Position 3 selects the outter coil for the neck humbucker, but the inner coil for the bridge humbucker.
Position 4 puts both humbuckers in parallel coils mode.
Position 5 puts both humbuckers in series operation.
The neck humbucker: That's where things spice up. A phase switch (orange) is inserted between the pickup and the selector. 1H goes directly to the switch, as does 2G. 1G and 2H get there too but after having gone through the mode switch. This allows me to switch the phase, regardless which mode I'm using, and allows for a cool range of bluesy hollow tones. From the phase switch then, one wire reaches the neck position of the selector and one wire goes to ground.
The tone controls: The neck and bridge pickups have each their own tone control (orange and purple respectively). The middle pickup has no tone control. Both tone controls have one side connected through the capacitor to the ground, while their other side goes to the selector switch, riding together with the hot wire from their respective pickup. This way, the controls are turned on only together with their respective pickup. NOTICE: Despite the fact that the neck tone's hot side seems to connect to the phase switch, it is in fact a permanently hot connection. It is not affected but the phase switch.
The blow switch (purple): Finally, the blow switch is exactly as described in the instructions. Nothing to add here.
 
 
 
Thank you for taking the time to read through this tutorial. I hope you found it helpful. Contact me of you have any particular suggestions or questions.
 
Enjoy!
- RG -