Rangebastard is an emulation of a Dallas Rangemaster. It has added controls for tweaking or for use as a full-range booster, an overdrive, and more.
All parts of the circuit are emulated, from the input filtering, to the interaction with guitar pickups, to the germanium transistor, and to the front-end distortion of a tube amp.
The Rangemaster was a germanium transistor treble boost developed in the 1960s. It and similar effects have been used by Eric Clapton, Brian May, and many more great guitarists. It’s most often used to drive a distorted tube amp into more distortion, while boosting the upper-mids for a screaming lead sound.