I bought a Behringer MDX1600 off ebay, well used. It was given a good review by bongomania as surprisingly good for the money. I'm using it with a Hartke HA3000, which has a single volume knob vs. gain/master knobs (may be important). Now, I've tried hooking this thing up every conceivable way--pre and post effect loops and straight into the front input--but the compressor, well, simply doesn't compress. You can twist all the knobs, push all the buttons, and it scarcely affects the tone at all. I have a Digitech Bass Squeeze, so I have some idea what should be happening. And almost nothing is happening. Only the expander/gate has any effect, and it just blows. Maybe the compressor is just broken, but while some some of the switches are a bit stuffed up, it basically appears functional. And I've tried both circuits; both are the same. The only other odd thing is that the input levels seem very low. They barely crack -18db. And while output levels can be adjusted, input levels cannot. So, are the input levels coming from my amp just too low for the compressor to compress? Without a separate gain knob on my amp, do I need a separate pre to boost the signal? Or is there something else I'm just missing?