They are at the heart and soul of your instrument but how do electric guitar pickups work and which clever person invented them? In this article we take a look under the bonnet of guitar pickups and hopefully answer the question how do electric guitar pickups work.
To better understand how electric guitar pickups work we must first delve back into the history of the discovery of electro-magnetic induction. The discovery of electro-magnetic induction has widely been credited to Michael Faraday in 1831. However, the less well known Joseph Henry also discovered the effect at the same time as Faraday but unfortunately for Henry it was Faraday who published his findings first and so continues to receive all the credit.
But what is electro-magnetic induction and what has it got to do with guitar pickups? Electro-magnetic induction sits at the heart of our question how do electric guitar pickups work?
Electro-magnetic induction is a physical phenomenon whereby a voltage is produced in a conductor when it is exposed to a varying magnetic field. Faraday first publicly demonstrated electro-magnetic induction in a now famous experiment on August 29th 1831. In the experiment he wrapped two wires around opposite sides of an iron ring. Faraday connected the first wire up to a battery and then connected the second wire to a galvanometer. When a current was passed through the first wire a measurable current was produced in the second wire. This happened both when he connected and disconnected the wire to the battery. The current produced in the second wire was caused by the change in magnetic flux in the iron ring caused when the first wire was connected and disconnected to the battery. Faraday, being the genius that he was, may well have foreseen the impact that this first experimental demonstration of electro-magnetic induction would have on society but it can be argued that it was one of the discoveries of the century. From Faraday’s ground breaking work scientists and engineers have gone onto to use electro-magnetic induction in a number of important applications.
The single coil pickup is constructed from a single or multiple permanent magnet wrapped with a single coil of copper wire.
Now this is all very good as a refresher lesson in secondary school physics but how does it all apply to a guitar pickup and how is it going to answer our question how do electric guitar pickups work? The answer lies in the construction of the pickup and the interaction of the pickup with the guitar strings.
An electric guitar pickup is usually made of a permanent magnet wrapped with a coil of several thousand turns of fine copper wire. The permanent magnets in the pickup magnetise the strings above the pickup and as the strings are strummed they become a moving magnet. The moving magnetic field created by the vibrating strings induces an alternating current in the copper coil surrounding the pickup. This signal is then amplified to produce the sound that you experience when playing your guitar.
The first successful pickup was developed by engineers at Rickenbacker in the 1930s who wanted to amplify their Hawaiian lap steel guitars. This first pickup was a single coil pickup in that it was made from magnets wrapped with a single copper wire. The pickup was highly successful and most guitar manufacturers rushed to include this new technology in their guitars. However there is an annoying drawback of the single coil pickup and that is it can produce a background humming sound. The problem with use a single copper coil is that the copper wire acts as a very efficient antenna picking up background electro-magnetic interference such as that generated by mains power cables. To overcome this issue the “humbucker” pickup was developed in the 1950s. Much like the initial discovery of electro-magnetic induction the discovery of the humbucker pickup was by two people working independently of each other on the problem. Joseph Raymond Butts is credited with the invention of the humbucker as he filed his patent for the development first. However, Seth Lover of the Gibson Guitar Company was also working on developing a humless pickup and filed his patent second.
The genius of the humbucker is that the coils are wound in the opposite direction to each other thus cancelling out the electro-magnetic interference that causes the hum in a single coil pickup.
The genius of the humbucker pickup is that it cancels the hum generated by the single coil pickup in a very simple way. The humbucker pickup has two copper wire coils wound in reverse to one another. The result of having effectively two single coil pickups wound opposite to each other is that they cancel each other out thus removing the irritating hum.
The modern pickup remains very much the same as the first pickups designed in the 1930s. They are still constructed from a magnet or magnets wrapped with copper wire. However, pickup manufacturers are continuously innovating to create some great sounding new pickups that will cater for any musical taste.
If you are interested in learning more about guitar pickups or other aspects of guitar construction and maintenance than we can highly recommend the Guitar Player Repair Guide by Dan Erlewine. In this great book the author takes an in-depth look into maintaining and repairing both electric and acoustic guitars. I would say this is recommended reading for any guitarist wanting to find out more about how to maintain their guitar. The book can be purchased through Amazon for £14.51.