Most guitar overdrive pedals tailor the sound before and after the clipping stage. This results in a loss of bottom end, as too much bass in an overdriven sound can make the sound "flabby". We take the signal from the bass guitar and split it. One path goes straight to the output via the DRY volume control, the other path goes through a high pass filter (to remove the flab from the overdrive) and then to a double clipping stage so as the signal level increases each different clipping stage contributes accordingly. This signal then goes to the CONTOUR circuitry and to the WET volume control. By changing the levels of DRY and WET you can easily vary the balance between the two signals. By keeping the original signal, we retain a warm bottom end and we add in as much dirt up top as is desired.
This pedal keeps all the bottom end you require, and adds in dirt, to get the sound of a cranked valve bass amp, at sensible stage volumes. The dirt helps you cut through in the mix, and pushes the bass where it should be, solidly front & centre.
Start with setting DRY to get unity output volume. Adjust WET to bring up some of the dirty signal, then adjust GAIN for the amount of dirt required. Set the CONTOUR switch for a brighter more modern sound, or a less bright more classic sound. Adjust the DRY and WET levels to get the required amount of dirt in the output signal.
DRY at 2:00, WET at 1:00, GAIN at 1:00 and CONTOUR switch up is a good place to start.