I would try just a couple of things before we proceed to investigating your amplifier. Just plugging the sub-woofer into the wall without an input source will normally cause the sub-woofer to hum. I would try putting a speaker wire into the high level input and see if it hums. The normal cause of humming is the RCA connector so this eliminates that possibility. If it still hums then I would contact Joe Vassallo at either joe@axiomaudio.com or 866-294-6688 and he will make sure to get it all working perfect for you.

Ian Colquhoun
President & Chief Engineer