As guitar players we’re familiar with the volume and tone controls on our guitars. Potentiometers (pots) – or variable resistors – have been used for decades on guitars, effects and amplifiers. There are two distinct types of potentiometers that we typically use for these applications: linear (often abbreviated as “lin”) and logarithmic (“log” or “audio”). Each of these types of potentiometers are used for specific applications, but first let’s break down what a potentiometer is, and how it works.
A potentiometer is a resistor that can be adjusted to control the amount of voltage running through a circuit. The most common construction uses three contact points: the middle sliding contact is called a wiper, and the other two ends contact to a fixed resistor called a track. The wiper is moved via a rotating shaft across the track to affect the resistance. The variable potential or voltage is obtained at the wiper contact as it is turned. It is a fraction of the fixed potential found across the track.
Linear potentiometers (like the name suggests) works in a linear way. The amount of resistance between ends of the track and the wiper goes up and down at a constant rate. If you were to map out the rate on a graph it would be represented in a straight line. This sort of potentiometer works fine for a tone control, but for volume controls linear pots can feel a little “off.”
The human ear perceives volume in a logarithmic way, but what does this mean? A logarithm is a mathematical term, so for those of you who finished school a long time ago like me, lets get a definition from Wikipedia.
“The logarithm of a number is the exponent to which another fixed value, the base, must be raised to produce that number. For example, the logarithm of 1000 to base 10 is 3, because 1000 is 10 to the power 3: 1000 = 10 × 10 × 10 = 103.”
So using a linear pot as a volume control would appear to have large obvious changes at low volume, and very little apparent change over the rest of the range.
Logarithmic pots are perfect for volume-type applications as they give the impression of a linear adjustment of volume, even though on paper they don’t. If they were to be graphed out the line would be curve, showing the exponential rate in which the resistance changes.
Seymour Duncan offer a range of high quality potentiometers. These potentiometers are high quality items custom-crafted by Bourns® to exact Seymour Duncan specifications. These audio taper potentiometers are perfect to use for volume or tone controls, and come in 250K versions for single coil equipped guitars and 500K for humbucker equipped guitars.
Also available are the Liberator solder-less pickup wiring system the amazing Blackouts Modular Preamp. These two products also have the same quality Bourns® crafted potentiometers built into them, providing smooth turning and rugged construction, ready to withstand whatever a guitar player throws at them.