you dont need to change or buy any 'bass boost' for the bass you are using.
for passive basses, turn volume full and boost/cut from amp.
if you amp has a gain control knob, DO NOT turn it up full or it will distort your tone. set it at 10 0' clock then increase or decrease volume as needed.
set you bass control on the amp to 1 o' clock, treble to 11 o' clock.
set the mids to 12 noon and cut / boost as you hear what sound you want.
pbass + flatwound = really yummy vintage sound. i love it...