Hello Herman, great question on the Supro drive pedal. Usually your chain would follow your melodica to a compressor pedal, volume pedal, then your Supro Drive pedal to a chorus, delay Etc. then reverb, finally out to your amp. I have found that if you use a preamp, in my case a D.I. pedal with EQ/boost first sincce the output of the Hammond does not push the pedal hard enough to maximize the pedals effect and tonal quality. I then follow to my API EQ/compressor to auto-wha then volume pedal to effects (vibrato, delays, chorus, Leslie pedals etc). And alway reverb last, then out to the amp to make tonal adjustments. Using an active volume pedal is good to keep the tone up in your chain if you have a lot of pedals on at one time but not sure it will solve the issue of a weak output of the Hammond. I have not used an expression pedal to control volume but please share once you decide. What amp are you running in your set up? The big problem I come across is that of trying to get a consistan balance from one melodica to another melodica when using effects without having to make manny adjustments to all the pedal set ups. At one time I was contemplating using a amp simulator pedal to see if I can control this issue but since I have a few amps to play with I have not. I use a EHX Cathedral reverb pedal which was fine for a while but looking to get either Eventide Space or Big Sky pedal, just not sure which I like best. what made you decide on the Big Sky pedal.