There’s very little information about this intense phaser pedal by Demiurge Instruments called Blackstone Phaser. Apparently, it’s an evolution of an obscure Blackout Effectors dual phaser that adds an extra rate setting – the two speeds can be switched through the Rate knob.
Each Rate knob has its own “Range” toggle that selects a range of speed, from slow to fast.
A series of toggle switches called Sweep, Stages, Vibrato, Asymmetry and Low Pass affect the quality of the effect in ways that are not always predictable.
As far as the tone is concerned and a more in-depth description of each control, we’ll defer to this demo by Pedal Experiments.