Custom Pot Tapers

Custom Potentiometer Taper Calculator

See how resistors connected between the wiper and either end of a linear potentiometer change its taper and the resistance presented to the preceding circuit.

Linear potentiometer value (kΩ) Unmodified resistance between pins 1 and 3. Resistor from pin 1 to wiper (pin 2), kΩ Leave blank for no resistor; this makes the first part of travel quieter. Resistor from pin 3 to wiper (pin 2), kΩ Leave blank for no resistor; this makes the first part of travel louder.

Wiper position

50%

0% (pin 1) 100% (pin 3)

Calculated results

Output at 50% rotation

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Output at selected position

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Resistance across pins 1–3 now

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Pin 1–3 resistance range

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Adjust the values to see the modified taper.

Wiper output versus rotation

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Original linear taper Modified taper Selected position

How the calculation works

Pin 1 is assumed to be grounded, pin 3 receives the input signal, and pin 2 is the output wiper. Each added resistor is in parallel with one section of the potentiometer track.

Parallel resistance = (R1 × R2) / (R1 + R2)

Wiper output (%) = 100 × lower section / (lower section + upper section)

Important: A shunt resistor does not turn a linear pot into a genuine logarithmic-track pot. It also changes the resistance measured across the two outside terminals as the wiper moves. This can load a preceding valve stage or tone stack much more heavily than the original pot.

This is an ideal, unloaded voltage-divider model. It assumes negligible signal-source resistance and no load connected to the wiper. Actual guitar-amplifier circuits may respond differently because of source impedance, grid-leak resistance and capacitance.

Background: Merlin Blencowe, Valve Amplifiers, 4th edition, Chapter 7, pp. 552–553.