The panning potentiometer (pan pot) is a variable control allowing an audio engineer to place a signal at different locations across the stereo field. With a stereo pair of loudspeakers, the pan pot changes the signal from the left side over to the right side.
The basic function of a pan pot is to change the amplitude of a signal in the left channel and also change the amplitude in the right channel. When the pan pot is turned to the left, the amplitude of the signal in the left channel is increased while the amplitude in the right channel is decreased. When the knob is turned to the center, the amplitude is identical in both channels.
There are several mathematical panning functions which can be used to determine the level of the amplitude should be for each channel based on the position of a (virtual) panning potentiometer. The first, and most intuitive, function to consider is the linear panning function.
Here are the steps required to calculate the linear panning functions. First, assuming the value of a panning knob can span a range from -100 (fully left) to 0 (center) to +100 (full right), this scale needs to be transformed to an amplitude value with a minimum of 0 (signal is entirely off) to a maximum of 1 (signal is entirely on). Any value of the panning knob between -100 and +100 should be transformed to an amplitude between 0 and 1.
The relationship between an amplitude, , and a pan knob value, , is: .
For linear panning, the amplitude of the right channel and left channel can be calculated:
rightAmp = x
Next, let’s consider another type: the Square-Law panning functions.