Electromagnetic Pickup Design
The Single Coil Pickup
Like the name suggests, the single coil pickup consists of a single coil, and multiple permanent magnets. The most common single coil pickup uses a copper winding and 6 permanent, cylindrical magnets one for each string.
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In general the signal is produced by the interaction between the steel string and the magnetic field of the permanent magnets. Let's consider just one section of the pickup involving the a single string and the coil surrounding a single permanent magnet.
Plucking the string will cause a change in the magnetic flux produced by the permanent magnet. This change change then induces a current on the copper coiled around the magnet. This interaction is modeled by Faraday's Law. |
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Faraday's law states that the electromotive force is equal to the number of turns in a coil(N) times the derivative of the magnetic flux with respect to time.
The small amount of alternating current that is induced in the coil is then sent to an amplifier which amplifies the signal and then the signal is sent to a speaker cabinet. |
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The Humbucker Pickup
One of the biggest problems from the design on the single coil pickup is that the magnetic field is sensitive to other forms of interference. Currents from a building's power, radio-frequency fields from consumer electronics, and the electronics inside audio equipment can all contribute to this hum, interference effect.
Luckily the Humbucker pickup design dramatically reduces this effect. The design essentially boils down to having two single coil pickups wired in series with the direction of the coils reversed. Both coils will experience the hum interference however since the coils are wired in reverse a reverse orientation the induced currents are always the inverse of each other. Wiring them in series has the effect of destructive interference, eliminating all hum.
Luckily the Humbucker pickup design dramatically reduces this effect. The design essentially boils down to having two single coil pickups wired in series with the direction of the coils reversed. Both coils will experience the hum interference however since the coils are wired in reverse a reverse orientation the induced currents are always the inverse of each other. Wiring them in series has the effect of destructive interference, eliminating all hum.
