Subwoofer ground loop: Earthing

[notnow]

Hello everyone,

I have an Onkyo TX-NR3030 AV amplifier and a Monitor Audio Silver W12 active subwoofer. The other components in my system are Monitor Audio Silver 10 front speakers, a Monitor Audio Silver Centre and Monitor Audio Silver 2 rear surround speakers.

Since I have had the W12 subwoofer, I get a hum when the subwoofer is powered and receiving a signal from the amp. If I disconnect the input cable from the subwoofer the hum disappears and there is no hum when the unit is powered on but not receiving a signal. If I switch input on the Onkyo, the hum stops whilst the input is changing but then comes back again as soon as the input has been changed on the amp.

I think this is a ground loop problem between the amp and the subwoofer. I have purchased an Audiolab Black Lab 5m subwoofer cable which is supposedly directional (it has arrows to show which end to connect to what component) and it also has two earth terminals which you are supposed to connect, one to the chassis of the amplifier and one to the amplifier body on the subwoofer. This is supposed to eliminate hum problems.

Does anyone have experience with these interconnects? What is the best way to connect the ground spade terminals on the lead to the amp and to the subwoofer? The sub does not have a ground screw. I was thinking of loosening a screw on the amplifier casing, removing some paint to get a metal surface and then securing the spade terminal down under the screw.

Is this the right approach? Any suggestions or advice would be gratefully received.

 

[laserman16]

What I did. Take a length of 3 core cable and strip out the earth ( green and yellow ). Throw the other two away. Fasten one end of earth to the amp ground and wire the other end into a 3 pin plug ( ONLY TO THE EARTH PIN). Plug into a socket but no need to switch the socket on and that should cure the problem.

Cured it for me anyway.

I'm not responsible for anything you choose to do.

 

[ellisdj]

Above is a good shout and it will work with any cable you don't need specific earth cable from inside a 3 core cable

If your not confident doing that the screw idea you suggested should also work just fine

 

[laserman16]

Above is a good shout and it will work with any cable you don't need specific earth cable from inside a 3 core cable

If your not confident doing that the screw idea you suggested should also work just fine

Agreed on the cable choice in that anything will do. The reason I used the earth cable was it was to hand and being coloured green/yellow it should leave anyone else in no doubt to what it is doing.