The Effect of Guitar Resistors

by Allison Horky
Resistors are bundles of carbon or metal wrapped around leads or wires.

Resistors are bundles of carbon or metal wrapped around leads or wires.

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Resistors restrict the flow of current in electric guitars. They are part of the circuit that takes the signal on the guitar and amplifies the sound. As sound is projected out of an amplifier, staticlike noises accompany the intended sound, because of the type of material your resistor is made from. The noise affects the circuit and thus the quality of the sound amplified from your speakers. The type of resistor you pick depends on your style of play and your amplifier design.

Resistor Materials

Resistors are primarily made with carbon composition or metal film. Carbon composition resistors are made of carbon, the conductor, and ceramic, the filler material. The lower the ratio of carbon to ceramic, the less resistance the resistor provides in the circuit. Carbon composition resistors have low wattage values. Metal film resistors are made from conductive metal oxide paste. They have very low wattage ratings. A spiral groove is cut into the resistive film -- the more grooves, the less resistance the resistor provides.

Tone Modification

The type of resistor in your guitar influences how the tone sounds when it is amplified. Carbon composition resistors were used in vintage amps popular in the 1950s and '60s. These resistors produced a lot of noise, or unwanted sound, in addition to having high drift, high pulse power and high variability. This means that the resistor does not handle high voltage being put across it without distorting the sound in some manner. This became associated with the sound of guitars before the invention of metal resistors. Metal film resistors hold up better in high-voltage amplifiers. The design allows for higher energy currents to pass through the resistor more easily than with carbon. There is less noise with metal film resistors.

Treble Bleed

Another effect that resistors have on guitar sound is treble bleed. Treble bleed happens when you turn down the volume on your guitar and the sound becomes muddled and messy. The electricity is searching for stability, a ground, and it does not project your high notes when the volume is being turned lower. Fixed resistors in guitars, also called volume kits, prevent the trebles from losing their edge as your amplifier decreases in volume.

Cost

Carbon composition resistors are the cheapest on the market because they are made from common materials. These resistors have also been manufactured longer than other types, making their production and design streamlined. Metal film resistors are among the most expensive on the market because they produce less noise. These resistors undergo more design and steps in production, such as the making of grooves in the film, than do carbon resistors. Price depends on the quantity ordered.

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