I am an electrical engineer myself and here are the facts again:

If the device has no metal parts which are able to carry a voltage there is no use for a ground earth, although a lot of notebook power supllies have one (The reason is that they have standardized connectors and there are standardized cables for these which are just cheaper because they are used for a lot of other devices as well which might need a ground earth).

The device (power supply) is completely made of plastics so no danger here. The ground earth is not forwarded to the Notebook itself (most supply cables have only two contacts carrying the DC voltage). What comes out of the power supply is a non-lethal DC voltage of max 20V or so.

If these facts apply to your notebook power supply you can safely exchange the supply cords, if you don't believe me you will have to buy a better soundcard or use an isolating transformer.

Greetz


On Wed, Aug 13, 2008 at 9:03 PM, Arnold Krille <arnold@arnoldarts.de> wrote:
Am Mittwoch, 13. August 2008 schrieb Martin Horn:
> On Wed, Aug 13, 2008 at 3:18 AM, Shawn Wallis <miesco251@gmail.com> wrote:
> > When I unplug my AC for my laptop, the noise stops...  WHen add
> > brightness to my laptop screen I get less noise...
> I suppose your laptop has an earth connection on the power cord. Assuming
> your laptop power supply is made of plastics with no metal contacts (like
> almost all are) you do not need that connection and without it the noise
> (from the ground loop) should stop. Just put some kind of isolating tape
> over the metal contacts from the earth ground (maybe two layers, because it
> might get cut when plugging in) and your ready to go. If you don't want to
> carry that tape with you all the time you should try to exchange your power
> cord (those from electric shavers looking like an "8" work sometimes).

And here came the advice of the stuff you shouldn't do.
Yes, it might fix your problem. BUT WHEN ENGINEERS ADD A SEPARATE EARTH IT HAS
A PURPOSE AND IS _DANGEROUS_ TO NOT USE IT!
Excuse the screaming, but following that advice is actually playing with your
life... only do that if you have a death wish.

Arnold
--
visit http://www.arnoldarts.de/
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