Subwoofer Hum!

[admin_exported]

I recently purchased the KEF KHT2005.3 with the upgraded cube 2 subwoofer to connect to my Denon 2310 Amp. Everytime the subwoofer is turned on and connected to the amp its makes quite a loud humming noice, which can easily be heard during quiet scenes or when watching normal TV. I found that without the subwoofer on the sound produced doesn't provide the depth that I would like.

I ran some tests leaving the subwoofer switched on without having the cable plugged in which is attached to the Amp and I didn't get any humming noice at all. When I plug the cable in and the amp is switched on the humming starts. Are there any suggestions? Do I need to purchase a specialist subwoofer cable? I realise I will probably get a hum no matter what I do but I can't see thats it should be as loud as it currently is!

 

[Andrew Everard]

Sounds like a ground loop from the amp being heard via the sub. Could be picked up on one of the interconnects, or could just be due to the way the system is plugged into the mains. Best way to track it down is to disconnect all your sources from the amp, then reconnect them one by one until the hum reappears. Then it's just a matter of plugging that component into another socket, or maybe re-routing mains cables and/or interconnects, until you lose the hum.

Yes, it is the devil's own job to track down the source of these things, but it's really the only way.

 

[wireman]

Apart from what Mr E has said, it's worth remembering that most AV equipment is double insulated (your Denon 2310 certainly is, the KEF HTB2 sub I had was also - your KEF cube sub is very likely to be too). This means that there isn't any direct connection at all to the earth in the mains socket. In these cases, the earth is "floating", and is carried (equalled) between components only by the earth pin in the signal sockets (phono sockets, HDMI leads etc). If all your equipment is double insulated (it'll be marked on the back of each component where it tells you what the voltage is, by a symbol of a square within a square) then it is especially important to ensure that all your signal lead plugs and sockets are very clean and make excellent contact, and none of the leads have broken/loose wires within them - any poor connection here will induce serious audible hum (there'll be a floating voltage on the earth, making it unbalanced between the individual components).

 

[Anonymous]

If it is humming it is generally because it has forgotton the words.