connecting a laptop to a P.A.system

  silverfoxx 00:57 28 Apr 06

I'm a musician and have started using a laptop to play my backing tracks. Using the headphone socket, the background noise is very noticable when the tracks aren't playing. I invested in an external sound card - Creative Live - but that is 10 times worse. The noise is audible even when the tracks are playing. The higher the volume, the worse the noise is. Does anybody have any ideas? The laptop is an Acer and is two weeks old.

  EARLR 13:11 28 Apr 06

Have you tried turning off your microphone?

  Roo247 14:03 28 Apr 06

I had a similar problem on New Years Eve at a house party. My friend hired an amplifier and speakers from a local disco shop and when my laptop was plugged in you got a nasty buzz coming through the speakers when no music was playing(luckily everyone was three parts to the wind and didnt notice!!)the only way to get rid of the buzz was to unplug the power adapter and the noise stopped(not good though when you dont have a huge battery life).Weird thing is I use the same laptop running through my home hi-fi amplifier, i get no noise, no buzz, just the music. My laptop is an Acer too if that helps.

  woodchip 14:11 28 Apr 06

AS above I think the Problem is the Old type equipment, as opposed to solid state electronic amp

  silverfoxx 14:04 29 Apr 06

thank you all for you're help. Earlr, how do I disconnect the microphone on the laptop when it's built in?

  amonra 15:00 29 Apr 06

It sounds a bit like mains "hum", ie. 50hz leakage or pickup being injected into the PA system. Try a good earth from the PA system amplifier to the laptop and keep the laptop away from all other equipment. Failing that, get a bigger battery supply for the lappy.

  silverfoxx 13:01 03 May 06

thanks for all the help. I've managed to find the problem. It's the power supply.

  frandenmath 16:29 19 May 06

Thanks for this - I too have an 'acer' and was experiencing the same problems - with your advice unplugging the power supply has meant I can play sound through an amp from the laptop without the background noise. Have you found a way to suppress the background sound whilst leaving the laptop plugged in please?

Thanks once again.

  octal 18:29 19 May 06

The problem you are getting is what is called a hum loop. What happens is the very small earth leakage from an item of equipment not only uses the earth wire but also uses the earth screen and earth wire connected to the amplifier.

The only way to safely remove the loop is to isolate the equipment from each other using audio transformers, something like these click here these are rather expensive, if you know an electronics engineer they can make one of these at a fraction of the cost, I've made plenty of them in the past.

  frandenmath 20:12 21 May 06

Thanks very much for your help here - I don't know an electronics engineer but will follow up the link you have provided for a supplier. I am just pleased that there is a solution.

Many thanks once again.

  octal 22:33 21 May 06

If it helps Behringer do on

click here

If you enter your location in the Dealer Locator it will return the nearest Behringer dealers in your area.

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