Wanna boost ? 20db of clean boost, with a bypassable (left switch) preamp (bass and treble control). Right toggle let you switch between the original “Grind” or the “33” EQ.
This, is a three in one, including the old school popular Integrated Preamp, switchable with the left toggle.
In "P" (Preamp) position, Bass and Treble became active. In "B" (Bypass) mode, you only have Level and EQ type control.