I emailed SVS already and thought I would post the message here for additional input. Hello. I have 20-39 PCi and am getting a slight hum from it. It is so slight I wonder if I'm just being overly picky, and have let it slide for awhile. But the curious part of me would like to at least have an answer, whether "that's just the way it is" or something practical. I am pretty positive it is not a ground loop problem as I have tried the standard test of removing the antenna/satellite cable connections from my system. Also since the power cable is two prong I figure that is not the issue. The hum goes away when I turn the receiver volume all the way down or when my DVD player is switching around the disc and apparently is not sending any kind of audio signal to the receiver. One thing that affects the volume of the hum is the crossover switch on the sub. When I switch it to "Enabled" the hum is less noticeable. I am wondering if something is going bad in my receiver's crossover circuitry if this is the case.