Loud Buzzing in External Speakers when PC AC Adapter plugged in

Posted on 2007-11-25
Last Modified: 2013-11-06
Having trouble with new DV9620US notebook.  Just purchased yesterday.

I was trying to watch a Nexflix movie on my TV through the HP notebook.  I do this with my Gateway notebook, as well.  And I used the Gateway last night to watch the movie because of the problem with the HP.

Here is the set up:  Cable Box inputs into DVD Player (AV-1).  Computer inputs to front panel on DVD Player (AV-2).  DVD Player outputs to TV & Speakers.

I use an s-video cord to connect from HP to DVD Player at  AV-2.  Then I use Audio Monster cable to connect to the sound ports on DVD Player at  AV-2.

When I plug in the power adapter into the HP I get a very loud buzzing noise through my external speakers (not te HP).  The noise is louder than the movie sound.  When I unplug the power adapter to the HP the noise goes away.  I  tried moving the HP away from the speakers.  This did not help.  

Any thoughts?
Do I need a replacement power adapter?
HP wants me to re-install audio drivers and power management. Does this make sense?
Question by:cjkurtz
LVL 19

Assisted Solution

pheidius earned 200 total points
ID: 20346273
It would not hurt. It would not take more than to minutes to do both. But is it likely to work? Probably not. It sounds like a grounding issue to me. Do you have any way to eliminate the svideo part of the link. I have never had good results  with svideo. if you did you would have more isolation options. ie pull video input and see if buzzing persists. or pull left audio then right with and without video out.

Author Comment

ID: 20347563
Thanks for your response.  I tried disconnecting the s-video, right and left audio, and it made no difference until I disconnected the power adapter to the HP.  I think you are right about the grounding issue from what I've read.  Could a bad power adapter cause the problem?

Author Comment

ID: 20347570
I will also re-load drivers just to eliminate them from the problem.
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LVL 19

Expert Comment

ID: 20347595
yea do that and you bark up their tree with more authority.
LVL 26

Accepted Solution

PCBONEZ earned 200 total points
ID: 20348435
Laptop power adapters are ~supposed~ to output nearly pure DC.
If you are getting noise with the adapter plugged in then the adapter indeed has a problem.
(It is letting AC and/or RF noise get through that the laptop's power circuit is not designed to handle.)
Long term use may in fact damage the laptop's power circuit and/or the battery.
LVL 19

Expert Comment

ID: 20353993
Bark loud up Hp's tree

Author Comment

ID: 20397582
A followup call to HP was useless.  They claim that if the power adapter chargers the battery and the laptop speakers don't buzz, then the adapter is not faulty.   The HP tech wanted me to plug in the adapter first, then turn on the laptop, which I did and did not make any difference.    When I plug the speakers directly into the laptop (and not through my DVD Player) there is no buzzing.   Should I bark at HP louder?
LVL 31

Assisted Solution

rid earned 100 total points
ID: 20397659
If you disconnect the sound cable and use the laptop's built-in speakers, is the buzzing still there (in the laptop speakers, that is)? If no, this is probably some kind of ground loop or similar and nothing that can be cured with drivers or similar. You might want to try another AC adapter for the laptop. Otherwise you need to make your setup more straightforward, making sure there are as few possible paths for ground as possible. Ideally, ground connection should have a "tree" structure and never loops. Ground can appear in signal cable shielding and in protective "earth" connectors in the AC plugs/cables.

Author Closing Comment

ID: 31410864
The advice did not provide definitive solution.  However, the advice is helpful to express my concerns to HP.  Thanks to all.

Expert Comment

ID: 20946329
i was just wondering if you ever got your static speaker problem fixed/.....I am currebtly having the same exact problem with my hp pavilion dv2000....please comment back.....i would really appreciate the help

Expert Comment

ID: 21496077
I am having the exact same problem aswell, the first one is with a Sony Vaio being plugged into my Amp, the second one is being plugged into the amp. As soon as one of the devices have external power added to them the horrible noise begins.

I was reccomended on the Zune Scene forum to try using thicker (higher quality cables) as the official Zune cable doesn't seem to have this problem (but that is not long enough for where I want to dock the Zune.

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