The Q-Spand is actually a pretty quiet mixer. If you are picking up that humm... It is either a defective mixer, or you have a ground loop problem (usually a problem if you have tt's hooked up incorectly, or poorly shilded RCA's running parallel to a power cord, or a laptop hooked up to the mixer that has a grounded plug). The eisiest way to troubleshoot is to unplug all RCA's going into the mixer. Then turn up the volume and see if you have the sound. If not then you start to plug in your inputs one at a time until the sound comes back. This way you can narrow down as to which piece of equipment is causing the problem. Also check to see if you amp has a ground lift switch and what position it is set to. I have also seen this type of problem come from a light controller mounted in the same rack. It grounds itself to the rack rails and comes through the mixer as noise. I have had this happen with a very expensive MP2016/XP2016 mixer with very very good S/N ratio.