Jonas Norberg has released PWMDrive, so called since it can produce sounds similar to a pulse-width-modulated square wave. It features "non-symmetrical" distortion and (optional) 8x oversampling - meant to be used at mixdown-time, since it's rather expensive.
The steps performed are:
- Measure the amplitude.
- DC-Offset signal depending on amplitude (LFO controlled).
- Gain.
- SoftClip.
- HiPass (to remove DC).
- Gain.
PWMDrive is freeware, uses the hosts default GUI and is available as a VST effect for Windows.