This is a bootleg equalizer. I used it constantly as a preamp (it gives a more natural scooped sound compared to something like a SansAmp). I found it helpful for correcting the sound when switching between 4-string, 5-string, and instruments with different characters, such as active and passive basses, using the SUPER LOW control. I am selling it to organize my equipment. Although there are changes to the knobs and some cosmetic damage, there were no issues with the operation. This is a sale of the unit only. ~Details~ The Deep Box is a new type of effector that can be used for both electric guitars and electric basses. The biggest features of this unit are the "SUPER LOW" control, which controls ultra-low frequencies that could not be expressed in compact effectors, and the "HIGH MID" control, which naturally brings out the mid-range that determines the sound of stringed instruments. By adjusting these, you can instantly change the sound output from the amplifier. For example, when connected to a bass, it is easy to process the sound of a passive pickup to sound like an active pickup.