There is a significant difference with some pedals. Try before, in the loop and after. There's also a way to rig things up with a loop pedal so you get to use a pedal both ways. The signal chain runs like this: bass-Qtron input - q tron effect out - fuzz pedal ( for instance) - loop pedal with the q tron effect return in the loop - loop pedal out - amp. Your signal will always be running through the envelope follower but you will be able to bypass the actual filter effect.