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H
 
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Default Inteference from laptop to monitor speakers

Hi,

Can anyone suggest what the problem is;

I have a pair of genelec acive monitors with xlr inputs on them running
directly from my laptop headphone socket (strange I know) and this provides
great low noise monitoring in a portable solution. However when my laptop is
running on mains electricity I get really bad inteference which sounds very
'digital' - for example when I move the mouse a noise that sounds like
digital artifacts is heard. This also occurs when I'm running the speakers
from my Yamaha 01x mixing desk when the desk is connected to the laptop by
firewire and the laptop is on mains.

Any suggestions?

Cheers,

H.


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Scott Dorsey
 
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H wrote:

Can anyone suggest what the problem is;

I have a pair of genelec acive monitors with xlr inputs on them running
directly from my laptop headphone socket (strange I know) and this provides
great low noise monitoring in a portable solution. However when my laptop is
running on mains electricity I get really bad inteference which sounds very
'digital' - for example when I move the mouse a noise that sounds like
digital artifacts is heard. This also occurs when I'm running the speakers
from my Yamaha 01x mixing desk when the desk is connected to the laptop by
firewire and the laptop is on mains.

Any suggestions?


Ground loop?
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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Zigakly
 
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I have a pair of genelec acive monitors with xlr inputs on them running
directly from my laptop headphone socket (strange I know) and this

provides
great low noise monitoring in a portable solution. However when my laptop

is
running on mains electricity I get really bad inteference which sounds

very
'digital' - for example when I move the mouse a noise that sounds like
digital artifacts is heard. This also occurs when I'm running the speakers
from my Yamaha 01x mixing desk when the desk is connected to the laptop by
firewire and the laptop is on mains.

Any suggestions?


This is a common issue with laptop built-in sound interfaces. You'll need
isolation transformers (a pair of passive DI's with ground lifts for
example), which will not help the sound quality, or preferably a dedicated
PC card or external interface, which will sound much better.


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Mike Rivers
 
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Zigakly wrote:

This is a common issue with laptop built-in sound interfaces. You'll need
isolation transformers (a pair of passive DI's with ground lifts


I agree that it's a common occurrence with laptops, but I'm not sure
that isolation transformers will solve the problem. Some crappy
built-in audio hardware just puts out noises like that. The difference
is that with the Genelecs rather than the crappy PC speakers, you can
hear it.

Give it a try, but buy your isolation transformers someplace where you
can return them easily if they don't do the trick. Ebtech makes what
they call the "Hum Eliminator" that's two channels in a smallish box.
Guitar Center and places like that (I know, what's like Guitar Center?)
carry the line, so that's a good place to buy, if you're anywyere near
a GC store. They'll take anything back as long as it isn't something
that gets too near your mouth (or your amplifier or drums either, if
it's a microphone).

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Zigakly
 
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I agree that it's a common occurrence with laptops, but I'm not sure
that isolation transformers will solve the problem. Some crappy
built-in audio hardware just puts out noises like that. The difference
is that with the Genelecs rather than the crappy PC speakers, you can
hear it.


I think you're talking about EMI from other componentry, usually the hard
drive and video card, this is much more severe. You don't hear it over PC
speakers because they don't create the ground loop. It would be plenty
audible with them too if it were present.




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Pooh Bear
 
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H wrote:

Hi,

Can anyone suggest what the problem is;

I have a pair of genelec acive monitors with xlr inputs on them running
directly from my laptop headphone socket (strange I know) and this provides
great low noise monitoring in a portable solution. However when my laptop is
running on mains electricity I get really bad inteference which sounds very
'digital' - for example when I move the mouse a noise that sounds like
digital artifacts is heard. This also occurs when I'm running the speakers
from my Yamaha 01x mixing desk when the desk is connected to the laptop by
firewire and the laptop is on mains.

Any suggestions?


Yet again ! In afew days ?

Isn't it time there was an FAQ on the subjct to point ppl to ?


*to the OP* - your laptop's mains power unit is causing the problem. The
'interference suppression' components that are required for regulatory approval
compromise the audio when there is another ground connection ( the low side of
the audio ).

Maybe one day the audio card manufacturers will fix this by providing balanced
outputs ? This is fairly unlikely though since most sales are aimed at the
consumer ( not the professional ) market.

Graham

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Pooh Bear
 
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Zigakly wrote:

I agree that it's a common occurrence with laptops, but I'm not sure
that isolation transformers will solve the problem. Some crappy
built-in audio hardware just puts out noises like that. The difference
is that with the Genelecs rather than the crappy PC speakers, you can
hear it.


I think you're talking about EMI from other componentry, usually the hard
drive and video card, this is much more severe. You don't hear it over PC
speakers because they don't create the ground loop. It would be plenty
audible with them too if it were present.


Mike has a point though. Some PC audio is truly dreadful, especially the
integrated motherboard implementations of 'sound cards'. Like on laptops for
example.

I've heard those 'birdy tones' and buzzes as you move the mouse etc.... on a
cheapo PC just by plugging in some decent hadphones ( no ground loop required
).

There is nevertheless entirely another issue regarding ( legal ) ground
leakage currents from the EMI filter.

Graham


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StraightEight
 
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I am receiving a similar problem with my Dell C610. I'm using an
external sound card, the problem seems to be the LCD screen, when I
switch off the screen the noise goes away, the only problem with this
is that it shoots up the latency in the sound card for some reason
(windows trying to do more than one thing at a time is always a recipe
for disaster) I've tried using an external monitor and then switching
it off when we hit record, but a monitor isn't always practical to drag
around when mobility is the key..the noise extends to the amps aswell
the monitors and so is being recorded...its a high pitched sort of
whine, not the usual mains hum...anyone have any ideas? The soundcard
is a transit USB.


Pooh Bear wrote:
Zigakly wrote:

I agree that it's a common occurrence with laptops, but I'm not sure
that isolation transformers will solve the problem. Some crappy
built-in audio hardware just puts out noises like that. The difference
is that with the Genelecs rather than the crappy PC speakers, you can
hear it.


I think you're talking about EMI from other componentry, usually the hard
drive and video card, this is much more severe. You don't hear it over PC
speakers because they don't create the ground loop. It would be plenty
audible with them too if it were present.


Mike has a point though. Some PC audio is truly dreadful, especially the
integrated motherboard implementations of 'sound cards'. Like on laptops for
example.

I've heard those 'birdy tones' and buzzes as you move the mouse etc.... on a
cheapo PC just by plugging in some decent hadphones ( no ground loop required
).

There is nevertheless entirely another issue regarding ( legal ) ground
leakage currents from the EMI filter.

Graham


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