Electric guitars generate sound by the virtue of strings vibrations which are converted to electric signals by pickups. That is how they differ from acoustic guitars that depend on acoustic radiations. Guitar pickups were invented by George Beauchamp in the early 30s. There are a few concepts that explain how guitar pickups work.
The Concept of Electromagnetism
Electric Guitars that use pickups are charged by electromagnetic induction. It is the same thing that works in a dynamo-powered light of a bicycle. A dynamo is an inductive sensor that converts mechanical energy into electric power like a generator. It consists of wires that are wrapped around a curved magnet. These wires cut though the magnetic field, creating a flow of current through the coil. In simple terms, a changing magnetic field induces electrical power. Also, a changing electrical field can induce magnetism. When coiled wires are connected to a source of power, a magnetic field is formed around them and this is what is known as electromagnetism- where a magnet is controlled by electricity.
How Electromagnetism Works in Guitar Amps
A guitar pickup comprises a magnetic pole wrapped with a coil of fine wire. The guitar strings (which act like dynamos) are usually made of iron and carbon or nickel and steel. These materials are ferromagnetic meaning that they can be attracted to a magnet. In this case, the pickups are the generators of electricity. These inductive sensors are set below the strings that vibrate to generate signals in the coil. The magnets in the pickups create a magnetic field that is passed through the guitar strings. The strings are partially magnetized and as they vibrate, a small electric current is formed and passed through the pickup coils. Because the pickups are connected to an amp in a circuit, the small electric current is boosted and sent to a speaker. This makes the familiar sound of an electric guitar. The speaker and the guitar amps are usually housed in a single unit.
According to the principles of electromagnets, coils and magnets have the capacity to change electric energy into vibrations or motion. Similarly, they can reverse the effect. So, the vibrating guitar strings generate a corresponding motion in the magnetic field of the magnetic pole hence sending a vibrating current to the coil. It is actually in the Faraday’s Law of Motion: a changing magnetic field sets up an electric field in a nearby wire, leading to a flow of current if the wire is in a closed circuit. This explains why a meter’s needle moves when a magnet is swiped across a meter connected to a coil of wires. The meter’s needle vibrates because of the changing magnetic field. The moving hand carries the energy of motion and is converted to electric current by the magnet. This is exactly how a generator works.
The Science Behind Guitar Strings
The magnet in the pickup forms a magnetic field that extends through the ferromagnetic strings above. The guitar string is magnetized as it vibrates, creating its own magnetic field. The coils that have been enfolded around the pickup detect or pick up this magnetic field. Then a tiny flow of electric current is formed. As long as the strings are moving and there is a changing magnetic field, then electricity must be produced and a sound must be heard. There is no sound without vibrations from the strings.
The simplest guitar pickup is made of a single coil. But it is prone to picking stray electric energy from unwanted frequencies like light switches and this leads to noisy distortions in the background. To solve this issue, some guitars that are designed with humbucking pickups. They consist of two coils arranged in a way that captures twice as much as the signal coming from the vibrating strings. Any stray signal that is captured from nearby electrical devices by one coil is cancelled by the second coil. With bigger magnets and high output, they produce richer and deeper tones like those of heavy metal and rock. Ideally, if you are seeking thicker sounds with higher output, a humbucker would come in handy. But for brighter sounds with a big twang, a single-coil guitar would be more suitable.
Does the Type of Magnet Matter?
Alnico (aluminum, nickel, and cobalt) and ceramic are the most commonly used magnetic materials for guitar pickups. Alnico magnets, which are more expensive than ceramic, are used in almost all vintage pickups. They generally give warmer and fuller tones with more prominent midrange than the ceramic counterparts.
Why Do We Have Different Guitar Effects?
Different guitars produce different sound effects. Most electric guitars feature at least two pickups – humbucker vs single coil. One pickup is placed directly below the fingers of the guitarist while the other one near the bridge or under the wrist. Depending on how the pickup is constructed, there can be a dramatic difference in the sound. Also, the pickup magnets are not created from the same materials. In other pickups, the coil of wires is very dense and thick. These factors explain the differences in the sounds produced by electric guitars and guitar effects. The amplifier connects to the pickup coils through a circuit. This circuit features volume control knobs that facilitate adjustment of the basic sound. An electric guitar with two pickups has 4 knobs on the main body. One is for changing the volume while the others are for adjusting the tone from each pickup. More circuits can be incorporated to alter the sound in various ways.
Sometimes, a guitarist might want to upgrade their instrument. Then they can add a step-up pickup to add more articulation, power, and depth to the sound. Installing a new pickup is something that can be done without technical help.