From Xotic:

“The AH Booster is an enhanced version of the Xotic AC Comp that Allen Hinds has been using for many years, refined to be even smoother sounding. With three compression modes and internal dip switches, you can choose your level of compression, tonal character and make subtle adjustments to treble and bass presence levels.”

Runs on a 9V battery or standard center negative 9V adaptor, or run at 18V for higher headroom.