If you want to show off your knowledge about guitars, then throwing into the conversation words such as potentiometer, or commenting on the use of electronic preamplification, or even simply remarking on the good use of purfling or kerfing, you’re sure to enjoy the blank look on the faces of those who thought they knew most things about guitars. In fact, these are all fairly common features when it comes to the design of electric guitars, but the terms and words are often ignored or forgotten.
So here’s a quick look at what some of these specialised terms mean. An acoustic guitar amplifies the sound of the strings being struck by using the hollow cavity of the body, but electric guitars work quite differently, and so the body of a guitar is usually solid. Pickups are used to detect the movement of the strings as they are struck, and this movement of the strings generates a small electrical signal which in turn is transmitted to an external amplifier. However, there can sometimes be a stage between the pickup detecting the movement of the string and converting this into an electric signal, and actually transmitting this signal to the external equipment.
A preamplification device is one built in to the guitar itself, and it is a preamplification device which boosts the voltage generated by the movement of the strings and detected by the pickup, prior to sending this boosted signal externally. By boosting the signal, a number of things can be achieved. A crisper and more precise note can sometimes be achieved, but more usually, a number of distortions or changes to the tone can be managed, with the adjustment of this preamplification device sometimes being used to quite drastically alter the tone or voice of the guitar, from a heavy sound to a shrill or twangy sound. A potentiometer is simply one of these electronic devices that interrupts the signal from the pickup to the amplifier, and allows the player to either boost the signal, or alter it in some way to create a different sound to the voice.
As far as purfling and kerfling are concerned, these are quite different, and refer simply to the ways in which the lining of a guitar is attached to the top, the back and the ribs of an acoustic or classic guitar. On acoustic guitars, the wood used for these parts of the body is very thin, sometimes being only just over a millimetre in thickness. So help strengthen the guitar, flexible strips of wood are placed in the corners of the inside of the body, especially where the rib meets the top of the guitar, and the back. In some guitars, particularly classical ones, these reinforcements are solid, but in acoustics, in particular those that are steel strung, the lining curved, or scored, and this allows it to bend in with the ribs. This is known as kerfing, and in some cases the outside joints of a guitar are routed out, and then filled with strips of material which help to bond the seams of the guitar together, often in a decorative way, this exterior, decorative binding is called purfling.
Both kerfling and purfling can be made using either wood, or in many cases today, plastic. On an acoustic guitar, if you turn it over to see the back, you’ll almost always notice that it is made from three sections of wood, and where these three sections join, there is a strip of material, usually decorative to some extent, and this is a good example of purfling. If you are looking at a steel string guitar, then look inside the joints, and you’ll be more likely to spot the kerfling.