In Pickupology 101, we took a look at the physics of how a pickup works, and we looked at several different single-coil pickups and how their differing constructions resulted in different tones. Let's take a look at humbuckers this month.
Humbuckers are basically double-coil pickups, which are wired both magnetically and electronically out-of-phase. This combination of out-of-phaseness causes the pickup to function in phase as a magnetic sensor, but it will cancel background electromagnetic interference, such as the stray electrons from neon lights, dimmer switches, computer terminals, etc. In a nutshell, humbuckers buck the hum.
This dual-coil construction has its own distinct tonal flavor. Compared to a single-coil pickup, humbuckers are usually darker sounding, more compressed (that is, a less dominant pick attack and more sustain after the initial attack), and higher in the output. The classic humbucker-equipped guitar is the Les Paul. Anyone who has switched between a Paul and a Strat or a Tele (two classic single-coil axes) knows the difference between single coils and humbuckers.
Curious sound-hounds might note that with two-coils, there are actually six different output possibilities for a humbucker: Each coil may be accessed alone, the coils may be wired in parallel and in phase, in parallel and out of phase, in series and in phase, and in series and out of phase. (All of these variations are also available with any single-coil guitar sporting two or more pickups.)
Here's a rundown of what these wiring variations sound like:
Each coil alone is essentially a single-coil pickup, but the proximity to the adjacent coil and the construction of the coil thats doing the picking up will affect the tone. The single coil sound will be lower in output and have more pronounced pick attack. Each coil will have a slightly different tone. Rewiring the high-output humbucker to access each coil alone is a great way to tame its tendency to sound muddy. Its a great trick for adding some sparkle and air, and makes for some excellent rhythm guitar tone.
Both coils in parallel and in phase will create a humbucking circuit, but the output will be less than the series-in-phase sound of the classic humbucker. Like each coil alone, this generates a good strum setting, just a little more compressed than the single coil mode.
Both coils in series and in phase create the classic humbucker tone, as I've described. Ninety-nine times out of one hundred, this is how your humbuckers are wired from the get-go.
Both coils in series or in parallel, but out of phase is a strange output. In theory, the two signals should cancel each other out, but because the two coils cannot occupy the exact same space, they sense slightly different portions of the string. The resulting sound is very low in output, and very thin. It's not without its uses, however. It can work well in a recording studio as a substitute for an acoustic guitar track. Pump it up with a high-gain amp or stomp box and you get an edgy, skroinky sound reminiscent of some of the Chicago blues players of the sixties. Mix it with another humbucker or single-coil pickup and you can get just enough zing to redefine an otherwise mushy sound.
Accessing all these sounds from one pickup requires some modification to your guitar. The more knobs you have, the more potential locations for switching possibilities there are. In future columns well look at how to rewire some standard circuits to get at these sounds. And if you've got some hip wiring tricks of your own, I bet a lot of readers would love it if you'd share them in the Guitar.com discussion boards.