New Subwoofer hums

[RoVic]

Bought a new active Subwoofer that hums when i plug the XLR cable in, even if the other end (RCA) is left out of the amps line out.
I was told by the seller (Shop) its because the woofer should be with a mixer?
I've been using my other Sub with the same Amp with no problems. i can't see how the amp can be at fault when the sub still hums even if not attached to the amp ..... any ideas please ??

 

[Member 639844]

Do you have a plug/cable that doesnt have the earth connected, chances are its a ground loop, which if so can sometimes be fixed with the above or with a mains conditioner. Something electrical plugged in may also be causing it, like a fridge etc, so you could turn things like those of one by one and see if the humming stops at any point. Again the fix for such things is as above, or if the plate amp on the sub has a ground terminal, you might want to connect it up.

 

[RoVic]

Do you have a plug/cable that doesnt have the earth connected, chances are its a ground loop, which if so can sometimes be fixed with the above or with a mains conditioner. Something electrical plugged in may also be causing it, like a fridge etc, so you could turn things like those of one by one and see if the humming stops at any point. Again the fix for such things is as above, or if the plate amp on the sub has a ground terminal, you might want to connect it up.

i have found out that if i unplug the XLR Cable from the Sub the hum stops, plugging it in with nothing attached to the RCA end make the sub Hum?? now I'm wandering if i have a faulty Cable ??

 

[hoppaz]

This may help...

http://www.avforums.com/forums/inte...-subwoofer-cable-causing-ground-loop-hum.html

 

[Member 639844]

i have found out that if i unplug the XLR Cable from the Sub the hum stops, plugging it in with nothing attached to the RCA end make the sub Hum?? now I'm wandering if i have a faulty Cable ??

Possible, but unlikely. You could try buying an XLR to phono adapter and using an ordinary phono cable to see if that makes a difference. An adapter would cost like £2 or something, so its a cheap test.

 

[hoppaz]

Possible, but unlikely. You could try buying an XLR to phono adapter and using an ordinary phono cable to see if that makes a difference. An adapter would cost like £2 or something, so its a cheap test.

Dont buy the adapter that is what I had it only worked using an all in one rca to phono pro cable.

 

[Member 639844]

Dont buy the adapter that is what I had it only worked using an all in one rca to phono pro cable.

Ive used the adapters before with no issues at all. I have an image to show this but its not working

 

[noiseboy72]

Chances are the cable is linking the screen to the cold signal pin. This will be the cause of the hum.

If this is a PA type sub, it will prefer a balanced line. You can get convertors for not a lot of money - £30 or so.

 

[hoppaz]

Ive used the adapters before with no issues at all.

Yes they may work in your case but they didnt in my case. For 9 quid the 10m pro rca to xlr lead I bought worked without any hum. The xlr to rca adapters share one of the connections with the earth which may make a grounding plane. Likewise the rca cable may pickup interference on the way and then ground itself.

Edit: what noiseboy said above except I have passive subs and an off board pro amp.

 

[Member 639844]

Yes they may work in your case but they didnt in my case. For 9 quid the 10m pro rca to xlr lead I bought worked without any hum. The xlr to rca adapters share one of the connections with the earth which may make a grounding plane. Likewise the rca cable may pickup interference on the way and then gtound itself.

Isnt the OP already using a dedicated XLR to phono cable though, I thought he was.

 

[hoppaz]

Isnt the OP already using a dedicated XLR to phono cable though, I thought he was.

He will have to confirm I read it as xlr and then rca at least we can move this toward a possible solution

 

[RoVic]

He will have to confirm I read it as xlr and then rca at least we can move this toward a possible solution

Thanks for all the advice / help ...... I've now sorted the problem it was a dodgy Cable got it replaced now the sub is sounding great !!