This filter plug-in compensates for non-natural linear mixer controls of cheap sound devices and give the volume bar of PM123 a nearly logarithmic characteristic.
You should not use this plug-in if your sound card already has a mixer with a logarithmic characteristic. You may check what kind of device you have with a simple test: Turn PM123's volume slider from maximum down to 50% while playing. If the volume decreases only a bit, you have a linear control and you should activate this plug-in.
Response of
the PM123 volume control
X-axis: relative position of the volume slider [%]
Y-axis: gain [dB]
The red line is the response function with the correction.
The green line is the response function of usual sound devices
without this plug-in.
Instead of an exponential function the plug-in uses the polynomial:
with x and y in the range [0,1] for the transformation. This
gives an approximately exponential function with a usable dynamic range
of almost 30 dB while keeping the zero point at -∞ dB.