Pedals on Sterling 4hh problems

Hi. New here and fairly new to Bass. Have a Sterling 4HH. I’ve recently been playing around with some effects pedals and have found that with the pre amp the pedals don’t really work. When I take the battery out the pedals work, but when I play clean the sound real dull and muted. Is there a fix for this? I’ve got an EHX Big Bass Muff PI and Boss Chorus pedal I’m using.

Thanks for any thoughts.