Subject: Re: [linux-audio-user] hum from laptop soundcard
From: Frank Barknecht (fbar_AT_footils.org)
Date: Sat Apr 19 2003 - 13:33:25 EEST
Hallo,
alex dray hat gesagt: // alex dray wrote:
> i think you're out of luck...the point of laptop architecture is to squish
> everything together....with a monitor and usb (which is fairly high
> voltage) so close to an integrated audio card, you cannot avoid magnetic
> influence as shielding at this level is practically impossible....you're
> best bet (and not a very good solution) is to get a breakout box so the
> actual dac is physically outside the laptop. If you come up with better
> solution please let me know,its a problem that frequently drives me nuts
An external box won't necessarily help, because it will not break the
ground loop, that is happening here. I have the same humming with a
Quattro. There is only one solution: breaking up the ground loop.
First one should try to disconnect everything that is connected to the
amplifier except of course the laptop. I had my main PC connected to
the same amp as my laptop and as soon as I disconnected the first, the
loop was gone.
If this doesn't help, then there is a ground loop between the amp an
the laptop itself. Then you need to break the earth connection between
the laptop and the amp (which is useless anyway) by using for example
a direct input box with ground lift or the Monacor FGA-40 filter.
One can also try to cut the earth of the laptop's powers supply if
one has a death wish... ;) I mean, don't do that.
I collect GroundLoop links on my Wiki:
http://footils.org/cgi-bin/cms/pydiddy/GroundLoop
ciao
-- Frank Barknecht _ ______footils.org__
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