Dual frequency-tripler circuit that uses crossover distortion
Distortion generator pedal
The Z.VEX Machine distortion guitar effects pedal uses crossover notch distortionn to distort when your guitar string is in the middle of vibrating, while it's swinging, not as it's turning around at the peaks. That's the same place where your speaker cone is sort of coasting, between all the way in and all the way out. Where nothing is happening, this pedal happens.