A guitar can be intimidating to modify, especially if you don't understand what's happening under the hood. This article is all about potentiometers ("pots") and what they do. A potentiometer is a variable resistor often used as an adjustable voltage divider.
Audio pots are a device's tone and volume controls, such as with an electric guitar, but they have many other uses. It's time to explain how pots work, why they're so crucial on electric guitars, and what to look for when shopping for replacements.
Volume and tone pots are the same component. The difference comes in the guitar wiring. The volume control pot affects the electrical output of the signal, and tone modifies frequencies. Guitar potentiometers work by passing an electrical signal from one side to the other when turning a knob. The higher the intensity, or resistance, the more power will pass from one side to the other.
Each pot contains a resistive strip and a sweeper (or wiper). The resistance strip is connected between lug one and lug three. When turning the knob, the sweeper attached to lug two moves over the resistance strip.
The third lug is grounded. As you turn the knob toward lug 3, more of the signal goes to ground. After it's fully turned, volume is at zero. If this lug isn't grounded, volume will not reach zero, rendering the volume pot useless.
Pots are split shaft or solid shaft. Be careful about finding the right size for holes and knobs. Push-on knobs go with split knobs. Knobs with set screws go with solid shaft pots. Do not use a screwdriver to pry apart a split shaft if it feels loose. The need to do this means you bought the wrong kind of knob.
Pot quality is essential. Just ask Cheech & Chong! You will generally find full-size pots and mini-pots inside guitars. Mini-pots (Alpha pots) are cheaper and less desirable. You see these in budget guitars. Upgrading existing pots is something to think about if you're going to mod your instrument.
Which Pot Value Should I Choose?
The best type of pot depends on the guitar modifications you have, as well as your personal preference. Higher resistance pots allow fewer treble frequencies to pass to ground, and the guitar will present a brighter tone. To increase treble, choose a higher value. For warmer sounds, go with a lower value.
A 250K pot is, therefore, the usual selection for a single-coil pickup (to smooth it out), and a 500K pot is the standard choice for a humbucker (to provide brightness and clarity). The correct choice is the resistance value that sounds best to you.
Active pickups usually use 25K pots, although any resistance between 25K and 100K should work. Output impedance is much lower in active pickups than in passive pickups. Using 500K and 250K pots with active electronics creates horrifically shrill tones. Actives, therefore, necessitate lower resistance pots.