Volume pedal / effects loop

[derekfrank]

I have a bass amp with built-in effects, and I'm using a stereo volume pedal directly in the effects loop to have a post-effects master volume. The volume with the pedal all the way up is significantly lower than the volume without the pedal/effects loop (dry). any ideas on why this is, or any solutions to this problem would be greatly appreciated. thanks! oh yeah, and it is the 25k pedal.