[quote name='Ghost_Bass' timestamp='1474458515' post='3138149']
Very true, but in this case i believe that he's not doing Bass > Pedal > FX Return, i think that the bass in still in the amp's input and the pedal on the FX loop FX Send > Pedal > FX Return.
Without more info from the OP we're just guessing now.
[/quote]
That was my point - putting a stompbox in the effects loop isn't normally something I'd recommend, although it works for some pedals it isn't guaranteed to work for everything, and will have a different outcome depending on whether the effects loop is serial or parallel or has a blend control.
What the OP should have done is bought an Envelope filter with a blend control!