I see, this is an all in one unit, not just a BD player, which makes sense because you said you were using a passive sub - that wouldn't have worked otherwise. Though those subs are similar, the amp most likely is not and that probably has to do with why it hums. So you are using the Aux outputs to go to the sub? Those sort of weren't meant for a sub; they are full range and are technically different than a preamp level output.