Hey RG, any possible internal issues aside... the master is actually the output level control (duh I know), but it's probably better to think of it like the input and output level controls on say a 1/3 oct eq unit, or any rack fx unit for that matter, wait that's what it is.... So the input and output level controls are so you can adjust for unity gain so the unit isn't boosting or cutting your overall signal albeit the sound has fx on it now, so obviously not like the master vol on an amp. So if the fx you have dialed in are boosting the volume (cumulatively as well) then you'll have to back off the master to suit. It's worth visiting each fx it goes through (internally) and getting their inputs and outputs right ) just as you'd do on a pedal board with them all in separate boxes.