I've just become the lucky babysitter of a TNA . Is it normal to have the sub volume dial on the amp barely off zero? It seems hyper sensitive on this machine, turning the sub up more than a hair off zero and it becomes way overpowered and rattles the shit out of the machine. I've also played with the crossover before anyone mentions that, as well as the bass, treble and volume dials ( the latter 3 only seem to affect the backbox speakers, it that correct? )