earth bridging

[cider]

perhaps somone can point me in the right direction to help solve a potential earth bridging problem on my home speaker / amp setup?

 

[Spark123]

What is the problem? Electrical noise caused by a loop?

 

[cider]

cheers for response. I have a constant loud hum or buzz coming from speakers and trying to find help on net to get it sorted. tried some hifi forums but users seem to be from another planet.
I know this isnt a normal household elecrical problem but running out of ideas to get it sorted.

 

[Spark123]

Is everything plugged into the same socket (assuming you are not talking about a large PA system!)?
What have you got plugged in which causes the problem?

 

[cider]

this is the embarising bit after a few too many down the boozer got on line and bought 1300 power amp and disco speakers size of phone boxes (slight exageration) for my 40th party which am now stuck with.
Currently got a mixer and ipod plugged in until the wife flogs them when im out one day

 

[RF Lighting]

Is the noise still present if you unplug all the inputs from the mixer?

What about if you unplug thre output plugs from the mixer (but leave them in the amp)

Are you feeding the ipod into a line input? Have you got the gain set too high maybe or the ipod output too high?

 

[cider]

the noise only goes if i unplug one of the two inputs to the amp from the mixer. they are not normal size hi fi plugs but 3 pin things with metal exteriors

 

[RF Lighting]

Do you have two leads from the mixer to the amp? i.e. one for the left channel and one for the right?

Is it one of these leads?

 

[cider]

yes but twin leads but mine look shi*e compared to those babies

 

[RF Lighting]

I don't know exactly what you mean by twin leads, but this would be favorite suspect.

Must hum on professional sound equipment is caused by problems with screen of leads before the amplifier.

You might find that it is just a snapped wire in one of these cables, but if you say they are not very good condition, it might be better to replace them.

You can pick up some mid - range quality leads for not a lot of money. If you post a photo of your leads, then someone should be able to provide you with a link for where to buy one from.

 

[cider]

thanks for your help my leads are normal stereo conection plugs one end and like yours other end on a twin cable. think they are a normal set converted to 3 pin one end.
i have had a quick look on some web sites and there seems to be quite a few different methods to connect amp to mixer and to confuse things there are loads of outputs/inputs to use on back of gear

 

[Spark123]

Can you upload a photo of what you have, i.e. the amp, the mixer and the leads?
Is the setup stereo or mono? How long is the lead? You have an XLR on one end and what on the other, have you connected both channels into the one XLR?
Have only used XLRs audibly for microphones before, is the input to the amp suitable for phono levels?

 

[RF Lighting]

My power amp has its inputs on XLRs

 

[cider]

View media item 6736took me ages to get that picture on there!

 

[sparkyspike]

You should be fine with TRS plugs (stereo jacks) and XLRs. It's possible that they are wired up wrong - US versions are wired up differently to European ones. Open both ends and check the connections are the same as each other. The Tip and Ring are normally left and right and correspond to L and R respectively. The remaining connection is the ground connection. Alternatively use stereo (balanced) jack-to-jack leads as the TRS inputs should be balanced anyway.