In the words of MXR:

The MXR Thump Bass Preamp is a tone-sweetening, signal-boosting, and
altogether groove-enhancing machine. This pedal was conceived when the
MXR design team and our in-house bass players discovered that the
Echoplex Preamps sonic secret sauce made for just as delectable a
pairing with bass as it does with guitar. Using that circuitry as a
foundation, the MXR team added a simple yet potent tone-shaping
interface so that you can dial in the perfect bass sound for the stage
and the studio.