What Causes A Car Amp and Subwoofer Ground Loop?

Question

I grouned the amp correctly as well as the line converter but i still get a loud hum out of the sub when the car radio is off, whats the problem, thanks!

Answer 1

Nothing. Because there is no reason to ground a sub to the chassis.  

You don't need to ground the line converter.

Do you have the amplifiers turn on lead wired to the ignition or to the remote wire on the head unit(radio)?

Reason I asked. wanted to make sure the amp is off while the radio is off.

Hope this helps