[linux-audio-user] noise from soundcard

Tommi Sakari Uimonen tuimonen at cc.hut.fi
Fri Oct 17 04:08:34 EDT 2003

> > Do you hear the same noise with headphones in the Sound Blaster card and
> > all other outputs/inputs disconnected from all cards?
> No!!  The noise goes away completely (and I get good signal levels)!  Cool.

I guess the Audiophile is more tricky to get headphoned.. (I have it too)

> > I suggest that you take your electricity for the computer and amplifier
> > and all that get's physically connected to them from one grounded outlet.
> > And beware if you have antennas connected to the system, they give ground
> > loop humming also.
> I tried putting everything on the same power strip and I still get the
> noise.  I have a mixer and an amplifier that the signal is going
> through, and I get the same noise going:

Then you should have all the equipment physically connected to each other
from their cases, like grounding them together. ** BUT BEWARE, THIS MIGHT
BE DANGEROUS. ** I don't know where you live, but in Finland the
electricity system is pretty darn safe and I wouldn't have any hesitations
to do so. There might be high voltage differences between the cases, so
all equipment should be disconnected from the outlet before grounding them
together. And take life insurance first :) And don't sue me if something
blows :)

Previously I had my gear in non grounded outlet and found out that the
voltage difference between my aplifier and computer case was around 240V,
but only for a fraction of a second because they got grounded together as
soon as they got physically connected throuhg the voltmeter. Of course
the current was not much so it was not lethal, but gave some nice snaps at
your fingers if you touched both. Then I got a grounded outlet and the
problem disappeared.

Unfortunately my aplifier doesn't have a grounded electricity plug, so it
still grounds through my cables, but the common ground is now same as the
real ground, which was not the case previously when the common ground was

BUT, if I have my vcr and radio connected to the amplifier, I hear
the humming noise at high volume levels. It doesn't bother in low volumes,
but if I were to record something, I'd plug out the antennas first. No
antennas -> completely silence.

Just make sure that all that connects to your computer (usb stuff,
firewire, monitor, etc.) don't cause the noise. Try plugging out all of

> > It appears to be system load based, it might be an internal voltage
> > interaction when your CPU goes from idle to active.  I've seen
> > this before.....   try to run this at a bash prompt:
> >   while true; do yes > /dev/null ; done
> This takes away a large part of the noise.  There is still some noise
> that sounds different, and I can still hear my mouse move.  When I move
> my mouse vigorously, it starts sounding closer to what it sounds like
> when that shell script is not running.

Try different PCI slot. But my guess for the mouse noise is the graphics
adapter. I remember in the old days with SBPro, that I had to choose ISA
slot that had the most distance to the graphics adapter, and still get
some high pitch whining. If it was closer, it got louder.

Do you have some motherboard integrated thingy or some real AGP card?


ps. Currently my amplifier is at recording studio and all I have is this
crappy portable cd-cassette-radio boombox. It has only mic input with
a 3,5mm miniplug. It gives me high whining noise and I can hear only the
left channel. And I'm ought to do some drum track editing due monday.. :(

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