Audio Interference

[Randomthom]

Hello all,
I'm having some issues with my laptop & I'd like some other viewpoints, hopefully experienced ones but I'm willing to listen to all!

When I connect my laptop via the Headphone jack to a sound desk input or even via the microphone jack to a sound desk OUTPUT I get a huge amount of interference coming out of the sound desk's main outputs. This is even the case if I run it via a USB sound card.

This is only the case with the power adapter connected, running from battery does not produce the same results. I know that it will stop if I cut the earth wire but for obvious reasons, I'm rather non-plussed by that idea. I also need it to pass future PAT tests!

Does anyone know of any reliable & safe method for cutting out this interference?

I'm thinking using an UK>EU then EU>UK adapters might work as EU plugs don't have an earth pin. It's a rather ugly solution though, I'm looking for something a bit more elegant, preferably not expensive though!

For clarification: It is NOT a 50Hz mains hum, it is a high pitched interference via the earth lead.

 

[pengipete]

Are you sure it's not just a shielding problem - i.e. the audio cables picking up interference from the PSU?

Is your deck set to receive line-level signals - if the channel is set to receive from a lower-level signal source such as turntable, you could have way too much gain which will boost noise from the cables. If you have variable gain as well as channel faders, drop the gain to zero and raise the level using the faders.

Does your deck/mixer have a ground lift - if so, engage that.

With the audio out from the lappy connected to the deck (volume etc set to normal), do you hear any noise if you flick the cable with your fingernail? If so, the cable is microphonic and needs replacing.

 

[vanthus]

Best solution I've seen for this problem Is to filter the output from the laptop going to the sound desk using an Audio isolating transformer.