how safe to remove an earth wire?

[Expertboy]

hi,

I have a seperate 750 watt amplifier which is powering 700 watt speakers. The problem i have is the amplifier is making a loud buzzing noise through the speakers when turned up even if there is nothing playing through it.

Now, if i remove the earth wire from the plug off the amp it is fine, so i guess it must be earthing back through the speakers.

So my questions are:

1. Is it safe to remove this earth wire and leave off?
2. If not, can i plug it into something like a Surge protector lead and leave the earth wire off, would this suffice?

Any help appreciated.

 

[electronicsuk]

No, you MUST NOT remove the electrical earth connection unless the amplifier is a class II double insulated device, which it clearly is not, otherwise there would be no earth connection in the first place.

You have what is referred to as a ground/earth loop, caused when the earth potential varies between devices in the system and allows a small current to flow between different parts of your audio system in places where it shouldn't.

Try unplugging all the audio inputs (phono, RCA connectors) to the amp and see at what point the audible hum disappears. Once you've diagnosed what's causing the loop, you can then look at ways of isolating it. Having both pieces of kit running off the same socket may help, otherwise you can buy a ground loop isolator for the audio side, or even try a filtered extension lead - I'm not sure the latter would help much.

FWIW, the earth loop is highly unlikely to have anything to do with the speakers.

 

[JohnD]

You say "a seperate 750 watt amplifier" so I deduce you must have separate sources (DVD, tape deck, tuner, whatever)


I've had that happen (but not recently) and you can bond the cases of the various items together so they are all earthed and there should be no significant current running through e.g. the phono cable outers. many electronic items are on 2-core cable so the cases will not be earthed or cross-bonded and may be at different potentials unless you bond them.

Some items have an earthing stud for this purpose on the back of the case, and so does 20" racking. I would always use G&Y insulated stranded for the bonding (2.5mm is plenty)

 

[Expertboy]

I appreciate all help here.

Ok, i have done what you have suggested and the humming stops also when i disconnect my 2 mixing desk leads that input into the back of the amp?

Is there any solution to stop this?, would a a ground loop isolator work on these leads?, would bonding the cases together work?

 

[Lectrician]

You need to lift the earth on one side of the phono leads, this will break the loop safely. Many amps or other audio kit often has an 'earth lift' switch. The decent stuff does anyway

 

[electronicsuk]

You need to lift the earth on one side of the phono leads, this will break the loop safely. Many amps or other audio kit often has an 'earth lift' switch. The decent stuff does anyway

Yup. Otherwise, something like this.

 

[Expertboy]

No earth switch, it is a decent amp though.

Now i have more of an idea i will experiment.

Cheers guys.