Buzzing from laptop

[powerMarkymark]

I want to connect audio out from laptop to home audio system to access my MP3 collection.

When I have it connected there is a loud buzzing sound.

I have narrowed down the problem- when I unplug the AC power cord from laptop and run on battery power- no more buzzing.

Why is the AC connector causing this problem.

TIA

M@rc

 

[hjo3]

First, have you tried other speakers/headphones? Assuming it still buzzes on different hardware:

The power connection is causing EMI and it manifests in the audio signal... try wrapping one cord in tinfoil or something. If it still buzzes, the EMI is probably coming across internally and there's probably nothing you can do.

 

[powerMarkymark]

Originally posted by: hjo3
First, have you tried other speakers/headphones? Assuming it still buzzes on different hardware:

The power connection is causing EMI and it manifests in the audio signal... try wrapping one cord in tinfoil or something. If it still buzzes, the EMI is probably coming across internally and there's probably nothing you can do.

Yeah, I've tried headphones (no buzzing), tried external speakers (no buzzing).

Then tried Creative SB USB external card and yup, got the buzzing.

M@rc

 

[powerMarkymark]

Any other ideas?

M@rc

 

[imported_rod]

It may be something to do with the USB card. Try running a cable from your laptop without using the creative card.

 

[powerMarkymark]

Originally posted by: rod
It may be something to do with the USB card. Try running a cable from your laptop without using the creative card.

I have tryed running with and without USB card and buzzing is presistant as long as the AC power is plugged in.

M@rc

 

[Markbnj]

Just a guess, but how close is the USB card to the transformer/rectifier part of the power cable?

 

[corkyg]

Move the A/C power brick as far away as you can - and, it would not hurt to put a ferrite core trap on the cord near the connector to the laptop.

And, you might also consider trying a different A/C/ adapter that has the same power output. What you are getting is A/C/ hum.

 

[powerMarkymark]

The brick is a good 4 feet away from the laptop and USB card.

There already is a ferrite core trap on the cord near the connector to the laptop.

I got the USB card to see if the humming persisted as it was there prior to the USB cards existance.

Gonna try connecting the laptop audio to another home audio system to see if the same thing happens.

Maybe have a problem with that particular receiver?



M@rc

 

[Markbnj]

Might be picking up something from the case, maybe if it is poorly grounded. Might also be a bad jack.

 

[powerMarkymark]

I tryed connecting the laptop audio to another home audio system and the problem is the same.

M@rc

 

[corkyg]

OK - you have probably a shielding deficiency where your external power connects to the laptop. If you are still under warranty, send it in. If not - your cheapest solution will be to disable the laptop's internal audio and use an external device such as Audigy 2NX or a PCMCIA audio card.

 

[powerMarkymark]

Originally posted by: corkyg
OK - you have probably a shielding deficiency where your external power connects to the laptop. If you are still under warranty, send it in. If not - your cheapest solution will be to disable the laptop's internal audio and use an external device such as Audigy 2NX or a PCMCIA audio card.

I bought an Audigy 2NX and the buzzing persists!

M@rc

 

[corkyg]

Bummer! That almost dictates that the case be opened and the grounding of that A/C connector port be looked at closely.

If it persists with a 2NX, then it is not only the internal audio circuit but the USB ports as well are affected (2NX is a USB connection.)

One more question - do you hear it through headphones as well?

 

[powerMarkymark]

No, not through earphones.

M@rc

 

[corkyg]

OK - then connect your speakers to the earphone port.

 

[powerMarkymark]

Originally posted by: corkyg
OK - then connect your speakers to the earphone port.

I want to connect to home audio system, not external speakers.

M@rc

 

[corkyg]

Originally posted by: powerMarkymark I want to connect to home audio system, not external speakers. M@rc

OK - then connect a patch cable from the headphone port to the home audio system AUX input.

Part of the problem could, in this case, be an impedance mismatch.

Also, consider connecting a ground wire from the laptop chassis to the home audio chassis.

 

[powerMarkymark]

Called Dell tech suppoirt and they are sending me a new A/C power cord.

Hope this resolves the problem.


M@rc