The difference between electric and acoustic guitars
Whilst this is an article about how electric guitars work it’s worth just having a think how they differ from an acoustic guitar.
It is fundamentally about how the sound they produce is amplified.
With an acoustic guitar, it relies on the strings, either metal or nylon, creating further resonance from the open box behind the strings, the body of the guitar, to produce a louder sound. The sound from the strings is amplified purely by the mechanical resonances of the guitar body.
Conversely, electric guitars (generally) have solid wood bodies with no chamber to amplify the sound – so how does it work?
Converting string vibration to voltage
An electric guitar, because of its solid body, relies on electronic means to amplify the sound of the strings. Without the necessary electronics on board the guitar and an external amplifier sound coming from electric guitar is very quiet indeed.
Electric guitars work by converting the vibration of the strings into an electrical signal. Placed underneath the strings on the body of the guitar are electrical devices called pickups. Typically, guitars have 1-2 or sometimes 3 pickups placed between the top of the neck and the bridge on the guitar.
The placement of these pickups and their relative volume creates different tones. A pickup placed near the neck will produce a sound that is more bassy and round it than one placed next to the guitar bridge which would be thinner and more trebly.
The pickup comprises a magnet and a coil of copper wire. When the string vibrates in the magnetic field of the pickup, it disrupts that magnetic field and induces a small current that is sympathetic to the note played. If you remember physics at school, this is a bit like a tiny generator or a motor that’s operating in reverse.
The signal well then pass through guitar’s volume control, sometimes called a potentiometer, and through a tone control. The tone control can be a simple passive capacitor-based circuit to limit treble or can be a more sophisticated active network that would be powered by a battery secreted in the guitar body.
The signal is then fed to the output Jack socket on the guitar ready for connection to an amplifier.
External amplification
At this point, the signal is still tiny just a few millivolts and requires further amplification before it is strong enough to power a loudspeaker.
This is the role of the amplifier which converts a tiny signal into something capable of producing some serious decibels.
Commercially made amplifiers range from one what to several hundred watts of power, with famous amplifier makers from the 50s and 60s still being very popular today, such as Marshall and Fender.
The overall sound
It is the combination of the player, the guitar, the amplifier type, and possibly the effects pedals that are being used to drive or overdrive the amplifier that creates the sound.
Classic rock and roll guitar sound is made by turning these types of amplifiers up very loud. You can learn more by visiting Guitar FX Direct online.
Overall, electric guitars are complex and fascinating instruments that rely on a combination of physics and technology to produce their signature sound.
Evolution of the electric guitar
As the electric guitar has evolved there have been many hybrids of acoustic and electric type of guitars.
In the early days of the electric guitar, electrical pickups were put across the sound hole of a steel strung acoustic such that they could be used with an external amplifier.
One of the early Gibson guitars that is still in production today, the ES 335 for example, is a semi acoustic guitar but still has electrical pickups so that it can be amplified.
There have been further evolutions to enable acoustic guitarists to amplify their instrument without having to resort to microphones. Piezo electric pickups, which work on very different principles to that of the normal magnet and coil type, are now used to great effect to allow classically shaped acoustic guitars, both nylon and steel strong, to be plugged in to an external amplifier or be fed to a mixing desk.