I believe the sound of the distorted ghost note you are talking about is the sound of a low bit-rate. What happens is you are truncating the guitar signal into a smaller and smaller number of steps which makes it look more and more boxy and adds a specific type of noise and distortion.
The normal 24 bit audio that we use in the pedal has 16,777,216 different levels at which the signal can be. This is such good resolution that doing things like turning the light on and off in your room will have more of an effect on your sound. However once you get down to 14 bits there are only 16384 different possible steps, 10 bit is 1024, and 7 bit is only 128 steps.
The result is that as you move from 20 to ~16 bits you'll get a bit of a softer and warmer sound with a bit more noise, as you move below 16 bits it will start getting much softer and you'll start hearing noticeable distortion and noise, it can even get a bit fizzy and spitty. Below 10 bits you will really start destroying the signal with very noticable distortion and noise.
Is this the sort of sound you were talking about? Was there something else you were looking to get out of the knob that you didn't find?