Notes on magnetic pickups and switching.
(This may be more than you care to know.)
There are two basic types of magnetic pickups. The single coil and the humbucker. The single coil pickup is just that, one coil. It is narrower than a humbucker. The humbucker is wider because it contains two coils wound side by side with one being wound backwards from the other. The reason for this is that noise from lights, motors, etc. will cancel itself out and make a much quieter instrument. The humbucker also will sound �fuller� because the two coils �sample� the string signal at two different places at the same instant. There are also some pickups that look like a single coil but really have two coils stacked on top of each other and are really humbuckers but still sound like a single coil because they sample the strings at the same place.
Some explanation of pickups may be in order. Whole books have been written on this subject so this will only be a brief overview. The basic magnetic pickup works by the action of the steel string generating a voltage by moving in a magnetic field. This is similar in theory to the way an electric generator works.
Using a humbucker pickup with two coils or two single coil pickups allows some different sound choices by the way the pickups are connected. The difference is in the switching possibilities with a pickup using two separate coils (humbucker), two or more single coil pickups, or two humbuckers with two coils each. I know that it's much more complex than this but, just for illustration, imagine the string's vibration in an instant as being sort of a very long moving figure "S" laid down parallel with the fretboard. You can see that the movement of the string over two (or more) coils is different. The string will be moving closer to one coil than another at a certain instant. If we combine the signals from the two coils so that they add together we get a full "acoustic" dulcimer sound (in phase). If we were to reverse the wires to one of the coils it would subtract from the signal (out of phase). We will get a hollow, treble sound. This "out of phase" sound is used by many Blues and Rock musicians. Additional coils or pickups work the same way depending on their placement and phasing.
The out of phase wiring of the pickups will produce a smaller output to the amplifier so the volume control will need to be increased to compensate.
Series/ Parallel wiring changes the impedance (electrical load) that the amplifier sees and changes the amount of inductance in the circuit. This changes the resonant frequency of the circuit and the signal sent to the amp. The change in sound is also very dependent on the amplifier or the first effect used. There are many switching schemes used in electric guitars, too many to list all of them here. The main ones are series/parallel, in phase/ out of phase with one humbucker or between two humbuckers and switching off one coil in a bridge mounted humbucker for a more �lead� sound. Using a humbucker at the bridge and switching off one coil instead of a single coil also gives us the option of using the two coils in humbucking configuration to reduce the possibility of hum.
The position of the pickup also makes a difference in the sound just like strumming over the fretboard sounds more mellow than strumming near the bridge. A pickup mounted near the fretboard sounds more mellow than one near the bridge. A pickup near the bridge has more of a treble or "lead" sound. This is especially true of the sound of a single coil pickup at the bridge.
Note: If you are reading all this to build your own electric dulcimer, welcome aboard! I do ask that you not copy my designs. I suggest that you use a �Blade� or �Rail� type of pickup. Don�t use the type of pickup that has the individual slugs under each guitar string unless you are planning to use standard guitar spacing for the strings. The guitar spacing is narrower than the standard dulcimer spacing and you will have problems with dead spots and string sound balance. There is a type of magnetic pickup called the "P Base". It looks like the perfect size for the dulcimer string spacing. Unless you are building a base dulcimer you probably won't like the sound.