Why is my subwoofer humming?

Question

I have a 5.1 surround sound system in my living room that has been working great for a few years until I moved to a new place. Now that I have been using it there is a loud hum coming from the sub. It's driving me insane and I don't know what to do. Any suggestions? Hummmmmmmmmmmmm!

Answer 1

It's either a "ground loop" or that the signal wires feeding the subwoofer amplifier are exposed to a strong AC magnetic field.  

Ground loops can occur in the safety ground on the AC line cords (if both the source and the amplifier both have three pronged cords), or they can occur between signal wires that go from one component to another.  

You could try disconnecting all other components and just leave one source and the subwoofer connected, or try disconnecting one component at a time.    

Another way to track it down is to unplug devices one at a time, leaving only your main amplifier and the subwoofer amp powered up.  If unplugging any of those components stops the hum, try getting one or more of those "three prong to two prong" AC adapters and putting those on the AC line cord, if it's a three pronged variety.   That should prevent a ground loop on the safety ground.  

(WARNING: Floating the safety ground will make that component into a potential shock hazard if the component is defective or if it ever becomes defective and it is not connnected to another, grounded component where the connection uses a chassis-to-chassis ground (ex: an RCA cable).    In practice, because the components ARE grounded to one another via the signal wire shields, the electrocution hazard is virtually zero as long as one component in the system is connected to the power line safety ground (so don't float ALL the components, leave at least one grounded).    

Answer 2

It's happy?

Try this:

- Fire up the system so the HUM is audible

- Disconnect the main CATV coax coming into your equipment

If the hum stops - you are getting 60 hz noise coming in from the CATV coax. You can call your CATV company and have them come out and ground the coax outside your house. Or you can get one of those power strips with coax connectors going in/out. Running the coax through this (with the AC power cord plugged in) will ground the coax.

Answer 3

Its a lead connection problem i'd say. Unhook all connections, double check everything and reconnect them all, if that fails it could be something to do with the internal amp of the sub (unlikely). But i'd go for the faulty connection.

Good luck.