Okko Twin Sonic Overdrive / Boost, controls for gain (distortion), clays (center knob), Cut (heights), Push (volume increase to 20db), Level (volume) and More (clean boost). HI / Low switch, HI switch position doubles the internal voltage to 18V for more dynamic, more headroom and tighter bass, operating with 9V battery or optional power supply 9V DC - internal (# 108096), made in Germany