This is distortion with very simple formula without complex and heavy formula like tanh , and it gives fat sounds like with analog synths. Inspired by Bezier curves but with two segments only , no need more.
It works with absolute values .
It has a normal behavior for values between -1 and +1 , and is designed to manage value up to -4 / +4 by a mirror effect generating a negative bump at the top with a buffer effect.
The core formula for the distortion is just of 3 blocks, the line in the middle, a cross fade between 0 and 1 level. It gives a classic distortion profile between levels 0 and 1 from a linear source with level between -1 and +1.
For the mirror part the values between 1 and 4 , are compressed to 0 - 1.
I use the same formula than for the normal part, multiply the result by 0.5 , then make the mirror work by removing the final value to 1 , for the deeper level of the bump at 0.5. The clipping of values above 4 happens at 0.5.
The final sound with the mirror effect is very fat, like you can hear in the demo.
There is a boost knob between 1 and 4, multiplying the input value.
I have added a delta knob for experimentation , adding a fixed value to the input value between - 0.5 and 0.5. The major part of the demo has deltas values ( we can hear an heavy cyclic effect by the PW ) , removed toward the end making the PW effect more fluid.