The Volume Switch goes the opposite direction as a booster - it reduces the signal instead of amplifying it. If a gain stage (this can be an effect pedal or the amp's preamp) is already overdriven, boosters usually only provide more distortion and compression - with the Volume Switch, you set your desired lead sound on your gain stage, and then passively reduce the level with the Volume Switch for less distortion and compression without colouring the sound - similar to the volume control on your guitar, but via footswitch and with adjustable treble bleed. It allows you to get a cleaner sound out of an overdriven tube amp preamp (basically adding another channel to the amp) or to get a second sound out of fuzz, distortion and overdrive pedals. High impedance volume control, reduces the level of the guitar without loss of treble to a value set by the knob, basically adding another channel to the amp. Can also be used as an A/B-Switch.