Have you ever thought about the different scientific properties of your guitar pickups? What materials are your guitar pickups made from? How do those materials work together to capture the sound of your guitar and reproduce that sound through an amplifier? What sort of processes are happening inside the pickup to produce sound? It is almost like magic that we can plug in an electric guitar, turn on an amplifier, and immediately create some wild noises!
How Are Electric Guitar Pickups Made?
Electric guitar pickups come in many different styles and shapes. The two most common arrangements are single coil and dual-coil or “humbucker” pickups. These styles can be “passive” meaning there is no external electricity in the system or “active” meaning an external source of electricity is present in the system.
Both types of pickups consist of one or more magnets made from alnico or ferrite around which a fine copper wire has been wrapped thousands of times. The magnetic field generated is focused by the pole pieces and then magnetizes the string. The oscillation of the magnetic field caused by the vibrating string produces a current that is captured by the magnet in the pickup and transformed into an electric signal that is reproduced through an amplifier.
What Do We Mean When We Say Output?
When we say we want to measure the output of electric guitar pickups, what exactly do we mean? As it turns out, it is very difficult to accurately measure output voltage from a guitar because there are so many variables in the measurement process. The true output of a guitar pickup is a product of the type of magnets used and the number of coil winds around the magnets. A more accurate measurement to determine the output of a guitar pickup is to measure what is called resistance.
How Do We Measure Resistance?
How do we measure the resistance of guitar pickups? What even is resistance? Yes, my guitar pickups will not sound the way I want despite how much I practice. Are my guitar pickups resisting my wishes? Yes maybe. But what we are looking for is a resistance in the electrical sense.
In this context, resistance is the measure of the pickup’s opposition to the flow of electric current. We measure resistance in Ohms using a device called a multimeter. You can pick up a multimeter at any hardware store. It is a useful tool for many different electrical measurements.
There are two important wires on the multimeter: the red test lead wire and the black test ground wire. To test the resistance of your pickups, you want to set your multimeter for Ohms and touch the red test lead of your multimeter to your pickup’s primary lead wire and touch the black test ground wire of your multimeter to the black ground wire on the pickup.
If you are testing a humbucker with four conductors, make sure that the wires are properly attached to each other. Make sure that the red and white leads are connected to each other and isolated from any other connection, and the green and bare leads are also connected to each other. Touch the red test lead from the multimeter to the black wire—the pickup’s primary lead. Touch the multimeter’s black test lead to the green and bare ground wires on the pickup. This should give you an accurate impedance measurement.
What Can Go Wrong?
Resistance readings can differ greatly depending on a number of factors including temperature, length of wire, diameter of wire, and the testing equipment you are using. If you test a pickup and you get a reading of zero or infinity, it means there is something damaged in the coil and your pickup will not work. Generally speaking, functional pickups range from 8k-25k ohms for humbucker style pickups and 6k-16k ohms for single coil pickups.
In general, the level of resistance is indicative of output between identical types of pickups. For example, a Seymour Duncan bridge position humbucker with a resistance of 8k ohms will be louder than the same exact pickup with a resistance of 7k ohms. However, as previously stated, the true output level of the pickup is determined by the type of magnet used and the number of coils around the magnet.
If science and electricity is interesting to you, then the guitar presents many points of interest. Go out to your local hardware store and get a multimeter and see what you can measure. You can use the multimeter to measure the output on your potentiometers as well as from the output jack. It might be interesting to find an older guitar to take apart and do some experiments with the pickups such as unwinding some coils to see how the resistance changes. Most pickup manufacturers list pickup resistance in their specifications and you are encouraged to check this out for more information! Stay curious!
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