I have a Berringer mixer 1000 and a pretty decent sound system along with a 1600w woofer. All sounds clear until I play from my laptop. It sounds like a record scratching with this costant hmmmm hmmmm. It's not feedback or a noise like that but an irritating noise. I'm using a Gateway laptop. I am going to try my laptop from work which is a Dell lattitude and see if that will make a difference but do any of you have any suggestions? I tried channels 3,4 and 5 and still get the same noise. I tried a different audio cable and still the same noise. Do you think a different laptop will do the trick or is it that particular brand of mixer? Any help is appreciated.

Are you using the built-in sound card, or an external?

Sounds like it might be a ground loop. There are devices you can buy to isloate it, like the HUMX.

Try running the laptop using the battery only (not plugged in to power). Is the noise still there?

Thanks Billabong I'll try that and let you know if that was the source

Did you ever get this resolved?

Yes it is now resolved. I actually tried a different laptop and POOF no more feedback (humming) noise. Thanks again

Definate \ground loop issue. Removal of the third pin using an adapter would have solved the problem.