The Torus Lo-Fi Fuzz is based on the Demo Tape Fuzz by Mid-Fi Electronics. The Demo Tape Fuzz is a throwback to the days of running a guitar into a cassette recorder and cranking the gain to overload it and create distortion.
The circuit consists of two simple building blocks. It starts out with an op-amp gain stage. This is similar to a Distortion+, so the low-pass frequency changes with the gain. (This is in contrast to most drive circuits after the 1970s where the potentiometer instead controls the feedback resistor, so the low-pass frequency remains constant.) Next, a basic Baxandall tone section allows adjustment of treble & bass.
The interesting thing about this circuit is that, like a cassette recorder, there are no clipping diodes, so all of the distortion/fuzz sound is generated “unintentionally” by op-amp clipping. It can get pretty thick, but retains its rough-around-the-edges character at all settings.
The Torus is a direct clone of the Demo Tape Fuzz with no modifications. The project is very low parts count and great for beginners.