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Annoying "hiss" from line out in laptop when using AC, Disappears when running from battery
kanak
post May 21 2007, 08:00
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Hi

I've got a dell e1505 with the onboard sound; I use my Shure E2Cs for listening. I've noticed an annoying hissing sound... here are the details

* The hissing sound is present when using earphones; it is not noticeable when using laptop speakers.
* The sound is present ONLY when using the AC adapter... when running on battery, there is NO hissing sound
* The sound is not "constant". When there is hard drive use, the hissing noise is supplemented by a different noise. This extra "noise" becomes louder as the hard drive activity increases. Again, the extra sound is non-existent when running from battery.

This hissing sound is a severe annoyance because my laptop is my ONLY means to listen to music. I've considered the following "solutions", but don't know if they are effective. Could someone please guide me:

* Using a ground lift (i read in some other thread that someone had a good result, but i don't think his condition was similar to mine)

* Getting a new PCMCIA sound card- I was considering getting the Audigy 2 ZS. Will it help? Given that the noise seems to be somehow related to power, am i right in believing that the audigy 2 zs will also suffer similar fate?

* Getting a USB sound card. Someone in another thread got a Behringer USB sound card and apparently it helped a lot. Again, it doesn't have an external power supply so I'm doubtful as to whether the problem will go away.

Can anyone suggest solutions / correct my above assumptions?

This post has been edited by kanak: May 21 2007, 08:02
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AndyH-ha
post May 21 2007, 08:11
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http://www.audiomastersforum.net/amforum/i...pic,6168.0.html
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PoisonDan
post May 21 2007, 08:20
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I've had this problem too. Getting a new sound card will probably not help, since I experienced it with both an Echo Indigo IO and a Firewire Audiophile.

I solved it using a ground loop isolator:
http://www.radioshack.com/sm-see-all-needs...pi-2062214.html

This post has been edited by PoisonDan: May 21 2007, 08:23


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AndyH-ha
post May 21 2007, 18:07
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That is one approach that sometimes works but you should probably look at the different approaches discussed in the thread I referenced.
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kanak
post May 21 2007, 18:32
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QUOTE (AndyH-ha @ May 21 2007, 03:11) *


Thank you for this very informative resource.


QUOTE (PoisonDan @ May 21 2007, 03:20) *
I solved it using a ground loop isolator:
http://www.radioshack.com/sm-see-all-needs...pi-2062214.html


I'm confused about the isolater. I can't figure out where the jacks would go. Could you give more details?
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craigbald
post May 21 2007, 18:53
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Try a 3 prong to 2 prong ground adapter. This is the cheapest way to get rid of a ground loop. You probably have one of these around the house anyway.
link
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kanak
post May 21 2007, 18:55
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QUOTE (craigbald @ May 21 2007, 13:53) *
Try a 3 prong to 2 prong ground adapter. This is the cheapest way to get rid of a ground loop. You probably have one of these around the house anyway.
link


Although my adapter has only 2 pins, I tried it just for the heck of it... no change.
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pdq
post May 21 2007, 19:54
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The power supply module for your laptop already provides ground loop isolation. Besides, ground loops only occur when you connect two devices that are both grounded through their power cords, and in your case you had zero.
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kanak
post May 21 2007, 20:06
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Something weird just happened.

I booted into safe mode without networking, and all of a sudden it was dead quiet (like running from a battery). I think the problem is with the driver (sigmatel driver) and i'm trying to fix it. I'll post updates.
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AndyH-ha
post May 21 2007, 23:14
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Ethernet cards do cause problems with audio in some setups. A separate hardware profile for audio, wherein the ethernet is disabled, may be a solution.
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hödyr
post May 22 2007, 00:41
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I had the same problem and solved it with a DIY shielded cable, I'm sure a properly shielded aftermarket cable (coaxial) will give the same effect.

pic 1
pic 2


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