[LAU] UA25 noise problem w. nVidia chipset

[Giso Grimm]

Hi,

On 04/07/2011 12:34 AM, Dave Phillips wrote:
> I've been working with Ardour3 on my laptop, a machine with an AMD
> Turion X2 CPU and an nVidia 8200M integrated video chipset. Recently I
> started monitoring my test recordings through the headphone output of my
> UA25 and I notice that when I move the mouse it creates scratchy sounds,
> though QJackCtl reports no xruns and my recordings are unaffected. I
> verified the problem with Ardour2 and Mixbus. It doesn't occur when I
> use the integrate audio chipset (snd-hda-intel, wahoo).

we observed exactly the same problem (only on the output of a custom
made USB sound card). The noise was spikes of varying amplitude at a
fixed rate (125ms if I remember well). Replacing the USB cable by a
shorter one significantly reduced the problem, and it also depended on
the USB ports used for mouse and sound card. On some mainboards/laptops
the noise was less then on others.

See
http://vegri.net/output_zero.png and
http://vegri.net/output_inactive.png
for output spectrum of the sound card (custom made, not UA25) when
playing zeros and when not in use.

- Giso

> 
> Running 'cat /proc/interrupts' reports that usb1/usb3 share interrupt 17
> and usb2/usb4 share interrupt 16. I've tried switching ports around but
> that didn't get rid of the noise. Any further suggestions ?
> 
> Best,
> 
> dp
> 
> 
> 
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