I know from past info provided by Marc at Skreddy that the Screw Driver is based, in part, on the old Univox Uni-Drive. The Throbak is obviously based on the Colorsound Overdriver. Both of the originals were transistor based (silicon) OD's that really hit the amp hard-neither of the originals had master volume controls. Has anyone compared both of these pedals. Hopefully Marc and Jon will chime in here also. I have owned and played D*A*M's custom shop recreations of the Uni-Drive and Colorsound as well as the Pro Analog Power Driver. All great. I would love to find something similar in a smaller footprint pedal like the SD or ODB.