On Sun, 4 May 2008 15:32:03 +0200 "Emanuel Rumpf" <xbran@xxxxxx> wrote: > Another noise problem: > Sometimes my mic-level shows a meter flickering in the lower range, > that doesn't seem to come from background sounds, thus creating > unacceptable noise... > At the moment it's gone, but it would be pretty usefull, to know where > it's coming > from and how to avoid it. electric / magnetic influences by other cables ? > > my setup: > low priced dynamic mic plugged via xlr into external ua-25 edirol usb > card (limiter on, phantom off). > the card uses usb power from the notebook. > neither notebook nor peripherials have any ground connection afaikt. What does the noise sound like? Do you have a sample we can listen to, preferable of what should sound like silence so that we know that anything audible is the noise? There are two obvious routes for noise to enter the system. 1. Induced into the mic lead or even the mic itself if the screening isn't so good. The sources for this can be nearby mains operated equipment, large transformers etc, microwave ovens, mobile phones and doubtless many others. Make sure the XLR connector is wired correctly, i.e. that the screen in the mic cable is attached to the ground connector. 2. Dirty power from the computer - the PC's internal power lines will have noise on them caused by things that suddenly take extra power, or use less like starting/stopping a hard disk, moving the heads, switching power saving/clock frequencies on the CPU etc. The interface may do a good job of keeping that out of the signal or it may not. If this second route is the one introducing the noise you may notice that the noise occurs at the same time as some particular activity on the PC itself. HTH, Steve. _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
