How potentiometers drastically influence your guitar tone

An important thing to realize is that your guitar tone is determined by all the different components that make up your guitar setup. One of the components that gets often overlooked is the electronics in your guitar, specifically the potentiometers (pot or pots for short). In this article we would like to tell you about the different types of potentiometers there are and how they drastically change your guitar tone.

What is a potentiometer?

A potentiometer is an electrical component that can be used as a voltage divider or variable resistor. They are commonly found in audio equipment to control the volume of something. A potmeter can take your guitar signal and only let a portion of it through (voltage divider) or allow another electrical component to influence your guitar sound more or less (variable resistor). The way it does this is by having an electrical contact that moves across a resistance track when you turn the knob. A noisy pot is often* caused by some dirt between the electrical contact and the resistance track. Turning the knob quickly a few times or using some special cleaning solvent can remove the dirt and solve the issue.

Resistance value

A potentiometer has a total resistance value. This is the value of the resistance track and is therefore the maximum resistance you have when the pot is turned fully ‘open’. This factor heavily influences your guitar tone as lower resistance values ‘soften’ the sound of your pickups. This softening is usually a good thing as pickups sound incredibly ‘spikey’ when hooked up directly to a guitar amp. The amount of softening you want is a matter of personal preference and is determined by the combined resistance value of your tone and volume pot(s). The most common used values in guitars from low to high are 250K, 500K and 1M where 250K is often used for single-coils and 500K for humbuckers.

The graph below shows you how the guitar signal changes with the use of different pot resistance. Notice that you don’t really get more higher frequencies in your guitar sound with higher values of resistance, only the resonance peak becomes stronger making the pickups more ‘pronounced’ and ‘spikey’.

The resistance value of the potentiometer also determines how gradual the tone control of your guitar works. If you use a 250K log pot (see Taper) then you get the most gradual sounding tone control (if the capacitor isn’t to big), where the high frequencies roll-off evenly, when you turn down the knob. If you use a higher value potentiometer (500k, 1M), then most of the high frequency roll-off will happen near the end of the dial. This is because the tone capacitor in your guitar will only noticeably roll-off high frequencies when there is minimum resistance between it and the guitar signal. With a higher value potentiometer, it will take longer before this minimum value is reached.

Taper

The taper of a potentiometer determines how the resistance changes when you turn the knob. There are generally three types: linear, logarithmic (log for short and often called audio) and anti-logarithmic. Linear means that the resistance changes evenly across the range of the knob. A logarithmic pot will have a massive change in resistance in the beginning when you turn down the pot and will change less when you reach the end of the dial. An anti-log pot is the inverse of a log pot, meaning it will change little when you turn down the knob and will increasingly change more when you reach the end of the dial.

You’d think that we’d always want to use a linear pot as it theoretically gives an even control, but there is an interesting catch. Our ears perceive sound in an anti-logarithmic way**, so we actually need to use a logarithmic pot in order to make a volume control sound linear! If you were to use a linear pot as volume control then its range will seem anti-logarithmic as most of the change happens at the end of the dial when you turn down the knob.

Use logarithmic pots in your guitar for both tone and volume if you are uncertain what to pick. You may however like the feel of linear pots more as this is really up for personal preference.

Source: http://www.resistorguide.com/potentiometer-taper/

Torque

High torque potmeters are more difficult and require more strength to turn than low torque potmeters. This is another thing that’s up to personal preference. High torque is handy when you don’t use your pots a lot so it’s harder to accidently turn them while playing. Low torque is essential when you use your potmeters during playing to change volume on the fly or do ‘violin’ like swell effects like you can do with our Pinky-Wah guitar system.

Specials

• No-load pots become an open circuit when you turn them fully open, therefore removing the potmeter from the circuit. Essentially you go from the pots maximum resistance on 9.9 to infinite resistance on 10. This makes the guitar sound more ‘spikey’ as there is one potmeter less to soften the tone of your pickups. No-load pots are used for tone control only as you’d get a mute switch if used as a volume control.

• The most common used knobs have an open case design where dirt could get in. There are also very expensive closed case designs on the market that are completely dirt free for life. These are essential if you use your potmeter during playing so you’ll never hear any noise when turning the pot. That’s why our Pinky-Wah guitar system comes with a closed potmeter.

Summery

A lot can be said about this simple component and we haven’t even talked about using potmeters in conjunction with other components like tone-capacitors! We hope you’ve learned something useful out of this article. Below we have a summary of the practical key points a guitarist should know.

• Noisy pots are often caused by dirt which can sometimes be resolved by quickly turning the knob or using special cleaning solvent.

• The higher the resistance value of the pots, the more ‘pronounced’ and ‘spikey’ the guitar will sound (even when all pots are fully open).

• Use Logarithmic (also called audio) pots for both volume and tone for the most gradual feel or if you don’t have a personal preference.

• The resistance value of the tone potmeter influences the feel of the tone control in conjunction with its taper.

* A pot also becomes noisy when there’s a DC voltage across it, cleaning won’t help in that case.

** We even think and behave in an anti-logarithmic way, but that’s a story for another time :)