Hum coming out of subwoofer:

There's an audiable hum coming out of my Audiophysic Luna sub. When I ran it parallel with the main speakers, the hum was there but when I run it through the Bat pre, the hum got louder and audiable up to 1.5 foot. Is this normal, or is there something wrong with the sub. I've try different powercords, connections, but none have worked so far. Any suggestions or light on the subject would be appreciated.
Is the sub a powered sub? If so, did you try floating the ground on the sub's plug (i.e., using a cheater plug)? Otherwise, maybe it's humming because it doesn't know the words (sorry, couldn't resist that one)?
Sounds like a ground issue if it is a power sub. I had the same thing happen with my REL sub. The REL has a third ground wire on the Neutrik cable. I had to change where it was connected to.

If not a power sub, try lifting the ground on your power amplifier power cord. Experiment around with a cheater plug.