Humbucking Pickups

A “pickup” is the name for the device on an electric guitar which picks up the vibrations of a moving guitar string and creates a electrical signal which can then routed to an amplifier. The easiest way to understand a pickup is to think about the electromagnet you might have made as a kid. Or, like me,  maybe the electromagnet you made for your kid. Remember? The big nail wrapped in wire and then connected to a giant battery? When the circuit was completed, the nail became a strong magnet and it could pick up steel things, like paper clips, smaller nails, etc.

Well a guitar pickup is similar to that but in reverse. In this case, instead of running electricity through the wire wrapped nail, you move a piece of steel (the guitar string) near a wire wrapped magnet and this produces a very faint and very weak electric signal in the wire coils surrounding the magnet. So instead of producing a magnetic field via electricity, when the steel strings move near the wire wrapped magnet, they produce an electric current. So electric pickups don’t “hear” a physical sound. They “hear” electromagnetic waves and turn that into electricity. You could almost say they hear radio waves. The sound produced by the strings and the wooden body and neck is incidental.

guitar-pickup

The problem with this simple design for a guitar pickup is that coils of wire also make an excellent antenna and so they pick up lots more than just the moving guitar strings. They pick up neon sign hum, AC power hum from your home, florescent lights, the motor in your fridge, etc. You hear this as a background hum in your amp and it can be pretty annoying, especially if it is loud. There are a few ways to deal with this and I’ll discuss another way in a future post but for now, I want to mention the mighty humbucker. The humbucker was invented in 1934 for use in PA systems and later in amplified pianos. In 1955, Gibson patented the humbucking pickup for guitars and of course the Gibson Les Paul was the first guitar to use humbuckers in mass production.

How do they work? On a single pickup, the polarity of a voltage induced in the pickup by the moving guitar string depends on the direction of the coils around the magnet and the direction of the magnet. A humbucker typically consists of two pickups, with the magnets in opposite directions and the wiring reversed. As a result of these two negative changes, the moving guitar strings generate the same signal in both pickups. Combining them results in a powerful signal. But the electromagnetic interference, from the neon signs and motors and stuff generate their own signals but only correlated to the direction of the wire winding, and not to the magnet direction. As a result, each pickup generates an interference voltage which is completely out of phase with the other. When these voltages are summed, by combining the pickups, the result is that the interference signals cancel out, leaving only signal – no hum. Hence the term humbucker.

mojotone-level-heads-humbucker

One thing Jimmy Page and others soon realized was that this boosted signal, coming from having two single coil pickups wired in series also produced a much louder signal. A high-output pickup sends a stronger signal to the amp, which means the amp distorts more readily. So humbuckers also ended up being the pickup early guitarists used when looking for better and more extreme distortion sounds.

For the Frankencaster, I chose two Seymour Duncan pickups, a model 59 for the neck and a JB for the bridge. My hope is that the JB is much “hotter” than the 59 and that I am going to see some serious crunch when playing on the bridge pickup.

The next trick is to figure out how to wire this guitar.

 

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