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Curious Inventor - Store: 100K Audio Potentiometer Carbon
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in stock - price: $1.99
100K Audio Potentiometer Carbon

short description:

24mm in diameter, this comes with washer and nut to fit into a 5/16" hole.

more information and instructions:

RoHS Compliant (lead-free). 300 degree rotation. Pins have holes for soldering wires. Audio means that the resistance changes by a logarithmic scale with respect to the knob angle, just like our perception of volume is based on the log of sound intensity.