I use it as "a second Channel". I play my Main Bass (active) over my 700RB-II with the WTDI bypassed. My other Bass wich I use Live for a few Songs is passive and I use the WTDI to adjust the Output-Level, so that both Basses are equal and I shape the Sound for this passive Bass with the WTDI..
: I call it the "get lost in the mix knob".