I Would try a different cable first.Also if you have some other preamp,or receiver(any thing with a variable output) ,try that too.When the receiver is turned off,most subs power
down.If the interconnect wire broke loose inside from moving things do to cleaning etc.,the sub woofer could recognize stray AC,or RF signals causing the hum and keeping it powered up.
down.If the interconnect wire broke loose inside from moving things do to cleaning etc.,the sub woofer could recognize stray AC,or RF signals causing the hum and keeping it powered up.