Le Fri, 20 May 2011 10:22:25 -0500, James Shatto <wwwshadow7@xxxxxxxxx> a Ãcrit : > That seems pretty regular at 8 to 10 minute intervals. Do you live > near a subway line? Or other electric mass transit option? Is the > computer on a UPS or power conditioner type supply line? I get a > spike like that when I use a battery box to power an electret mic. If > I turn it on after pressing record. Beyond that, your guess is as > good as mine. > > - James > Such spikes can have 2 origins, from the main or from the air. If they come from the main, a good quality main filter can help to reduce them, but sometime it can increase them, so it is no absolute rules here. If you have external devices connected to the main and to the audio path, they must have an electrostatic shield between the primary and the secondary of their main transformers. Separate the audio cables from the main cables. Be vary careful with those cheap main adapters (transformers) that come with a lot of low voltage devices. Many of them are so cheap that they will have no effect on, or can even increase the high frequency noise (like such spikes) coming the main. The best solution here is to replace them with small stabilized supplyes. You should also pay attention to the earth. For all the audio related devices, you must have a earth, but only one. For that and if several devices are earthed, their power cords should be connected directly to the same earthed plug. (As example, with 3 devices, it will make an Y with the plug at the centre of the Y). Use good quality extension cords. If they are too long, they should be completely unwound. If the spikes comes from the air, it can be very complicated because the best solution is to eliminate the source. If it is not possible, only shields will help. And of course a good and unique earth. For the shields, use good quality shielded audio cables and connectors, prefer symmetric connections when possible over asymmetric ones. Ciao, Dominique > > On 5/20/11, Peter Hoffmann <ph@xxxxxxxxxxxxxxxxxx> wrote: > > Hello, > > > > I'm recording audio 24/7 with a delta 1010 sound card and have a > > strange problem: > > > > Every night at 2:30 I get spikes and some inaccurancy within some > > seconds in a one hour length recording. I've upload a screenshot to > > illustrate the problem: > > > > http://img88.imageshack.us/img88/4562/spikesh.png > > > > My .asoundrc > > > > pcm.capt { > > type dsnoop > > ipc_key 223456 > > slave { > > pcm "hw:0,0" > > rate 8000 > > period_time 0 > > period_size 320 > > channels 12 > > format S32_LE > > } > > } > > > > pcm.c1 { > > type plug > > ttable.0.0 1 > > slave.pcm capt > > } > > > > pcm.c2 { > > type plug > > ttable.0.1 1 > > slave.pcm capt > > } > > > > pcm.c3 { > > type plug > > ttable.0.2 1 > > slave.pcm capt > > } > > > > pcm.c4 { > > type plug > > ttable.0.3 1 > > slave.pcm capt > > } > > > > pcm.c5 { > > type plug > > ttable.0.4 1 > > slave.pcm capt > > } > > > > pcm.c6 { > > type plug > > ttable.0.5 1 > > slave.pcm capt > > } > > > > pcm.c7 { > > type plug > > ttable.0.6 1 > > slave.pcm capt > > } > > > > pcm.c8 { > > type plug > > ttable.0.7 1 > > slave.pcm capt > > } > > > > I'm recording with arecord -q -f cd -t wav -d 3600 -c 1 -D c1 > > out.wav. > > > > Any hints where the problem might be? > > > > Kind Regards, > > Peter Hoffmann > > > > ------------------------------------------------------------------------------ > > What Every C/C++ and Fortran developer Should Know! > > Read this article and learn how Intel has extended the reach of its > > next-generation tools to help Windows* and Linux* C/C++ and Fortran > > developers boost performance applications - including clusters. > > http://p.sf.net/sfu/intel-dev2devmay > > _______________________________________________ > > Alsa-user mailing list > > Alsa-user@xxxxxxxxxxxxxxxxxxxxx > > https://lists.sourceforge.net/lists/listinfo/alsa-user > > > > ------------------------------------------------------------------------------ > What Every C/C++ and Fortran developer Should Know! > Read this article and learn how Intel has extended the reach of its > next-generation tools to help Windows* and Linux* C/C++ and Fortran > developers boost performance applications - including clusters. > http://p.sf.net/sfu/intel-dev2devmay > _______________________________________________ > Alsa-user mailing list > Alsa-user@xxxxxxxxxxxxxxxxxxxxx > https://lists.sourceforge.net/lists/listinfo/alsa-user -- "We have the heroes we deserve." ------------------------------------------------------------------------------ What Every C/C++ and Fortran developer Should Know! Read this article and learn how Intel has extended the reach of its next-generation tools to help Windows* and Linux* C/C++ and Fortran developers boost performance applications - including clusters. http://p.sf.net/sfu/intel-dev2devmay _______________________________________________ Alsa-user mailing list Alsa-user@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-user
