Circuit for volume contour with standard potentiometer

This circuit shows an aural matching volume control circuit (loudness). It adapts to the frequency-dependent auditory sensitivity by raising lower and higher frequency components at lower volumes.

In contrast to the otherwise known circuits, as can be seen in an above-shown circuit with tone controls, this requires no potentiometer with taps. The pot should have a linear characteristic. For stereo, of course, a tandem potentiometer and the circuit is needed twice.