A little known fact: The arrows in the SansAmp controls indicate the unity-gain position.For best results, don’t set the Pre-Amp level lower than unity gain when the Drive knob is at 9 o’clock or higher. However, if you want a crystal-clear sound and the Drive control is already near minimum, decrease Pre-Amp to further remove distortion.To create varying types of overdrive, vary Pre-Amp in relation to Drive. A high Pre-Amp setting emphasizes pre-amp distortion (see “Mark 1” preset), while high Drive settings emphasize power amp distortion (see “Plexi” preset).