[linux-audio-user] hum from laptop soundcard

[Frank Barknecht]

Hallo,
derek holzer hat gesagt: // derek holzer wrote:

> yes,
> 
> same here. it is very common for laptops to have terrible ground loop 
> problems when connected to other equipment, which is what you are 
> hearing. the two solutions i can think of:
> 
> a ) use a DI box between your laptop audio output and everything else to 
> lift the signal off ground--an expensive option if you are just using 
> the headphone out, of course!

You can also use the Monacor FGA-40 filter, which lifts ground, has
two cinch connectors on either side and costs just 17.20 EUR. It is
available in car audio shops or online for example here:
http://www.power-discounter.de/p3721.html
(Germany)

> or  
> 
> b ) find another way to remove your laptop from ground. using batteries 
> is one, but then your processor slips into a lower mode and you lose 
> some of that computing power you paid for. a friend suggested using a 
> powerstrip that either has no ground or has had its ground removed. 
> haven't tried it yet, but that sounds like the best bet. 

Well, epanorama calls this solution the "cheater plug" and doesn't
recommend it:
http://www.epanorama.net/documents/groundloop/problem_solving.html

> better than  hacking the grounds off your AC adaptor, at least... :-)

The result is the same as the ground-less plug and thus might be 
dangerous, as well.

ciao
-- 
 Frank Barknecht                               _ ______footils.org__