Pickup Lines
In the first part of our focus on pickup controls, Bare Knuckle Pickups’ tech support ace Tim Bartle explains why not all pots were created equal…
Some players will only touch their guitar volume control to check it’s turned up full, while others constantly rely on it for a variety of tones and techniques. In either case, the humble potentiometer that resides beneath the knob, out of sight (and often out of mind) plays a vital role in the sonic picture. To find out how different types of potentiometer can bring out the best in our pickups and performance we spoke with Bare Knuckle Pickups’ resident expert Tim Bartle.
“Potentiometers, or ‘pots’, are a type of resistor,” begins Tim. “There’s a fixed resistance between the outer contacts,
“Logarithmic pots are great because you can get a large swell of volume with less than a quarter turn”
but the middle contact is a wiper that can slide from one end to the other and take a split from anywhere in the middle. In other words, you’ve got a fixed resistance between two points but you’re able to tap it at any point in between. So, with the pickup attached at one end and the ground attached at the other, you can get anything from full signal down to zero signal with the output from the middle contact.”
The way in which the resistance of a pot changes as the wiper is moved – namely, the knob is turned – is known as ‘taper’. The two most common types of potentiometer used in electric guitars are linear and logarithmic (also known as audio) taper pots – each being preferred in a variety of different situations.
“Taper means the way the resistance changes from one end of the pot to the other,” says Tim. “In a linear pot, it changes at an even rate: halfway across the resistor means half the resistance. It’s a straight line. Whereas a logarithmic potentiometer is a curve: from zero, you get a much flatter rise in resistance and then the curve gets steeper towards 10. There’s also a reverse logarithmic pot with a steep curve from zero, which flattens out towards 10.
“Different types of pot tend to suit some playing styles better than others. For example, linear pots feel like a smoother progression. As you roll up from zero, it will be a very even and gradual rise to full volume. So if you prefer to have your volume rolled quite far back – maybe set at half volume for some low-gain work – a linear pot will probably be easier to control and dial into that medium range. But then if you wanted to do swelling effects, having a logarithmic pot is great because you can get a really large swell of volume with less than a quarter turn. A typical application for a reverse logarithmic taper pot would be for left-handed players where they want the pot to work as a regular logarithmic pot.
“Pot values have become standard in different guitars because that’s what they used in the vintage classics, although I’m sure they didn’t arrive at those values by accident. The resistance value of a pot has a significant effect on the overall brightness of the guitar. The input of your amp, pedals, cables, pot resistance and the inductance and capacitance in the pickup all work together almost like a filter control. By changing the resistance value of the pot, you’re modifying the overall load on the pickup. With a higher resistance [pot value] you’re shifting that filter frequency upwards, so you hear a fuller range of the pickup. And as you bring the pot resistance down, you’re allowing more of those higher frequencies to leak off.
“Fender’s use of 250k pots is a great pairing for their single-coil pickups because it balances the tone. And, likewise, with Gibson-style humbuckers, a 500k pot can give you a more balanced sound as the tone is naturally fatter. We have our [550k/280kohms] CTS pots custom made. The slightly higher resistance opens out some of the higher frequencies, revealing more treble detail from our pickups. Of all the great-sounding vintage pots we tested, the ones with the most vibrancy always had a higher resistance.”
“Fender’s use of 250k pots is a great pairing for their single-coil pickups, because it balances the tone”