-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Wed, May 16, 2007 at 11:52:35AM +0200, Pieter Palmers wrote: > Ken Restivo wrote: > >-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 > > > >I've noticed a nasty aliasing noise when connecting an analog output > >from a digital source, to the analog input of another digital device. > > > > > >For example, going out of a cheap soundcard on a PC, into a nice (or > >cheap) A-D converter, an ugly high-pitched aliasing noise appears > >even with no program data. It's not audible to my ears when listening > >just to the analog output of the hda-intel; one must plug its output > >into an A-D in order to hear it, and then it's rather loud. > > > >I've noticed this with my expensive Edirol firewire interface and > >with my cheap Audiophile USB interface. The common factor is when the > >sound being digitized comes from an ugly hda-intel sound chip. All > >three are running 48khz > > > >Would this happen even with expensive D-A's? Is this a common > >problem when connecting D-A back to A-D? > > > >I'm asking because I'm going to have to plug the analog outs from one > >of these interfaces (the firewire or the USB, not the hda-intel) into > >someone's PresonusFirebox/ProTools rig on Friday, and I want to know > >if I'm going to have to deal with this aliasing noise. > I don't think this is aliasing noise since the HDA will have some sort > of reconstruction filter, and the Edirol/MA-Audio interface will have a > decent anti-aliasing filter. > > It will probably have to do with the power supply noise rejection of the > codec attached to the HDA chip. Or the headphone amp that is definitely > present in it. The load presented by a headphone (can be as low as > 32ohm) is different from the load presented by a device input (multiple > kiloohms). This can cause a change in PSSR behavior. It's related to > ground-loop type of behavior. (if you can make the sound change by e.g. > moving the mouse or changing the stuff displayed on the screen, most > likely you're seeing bad PSSR. The sound comes from the dc-dc converters > from the LCD panel). Yep, that's probably it then. The sound squiggles and chirps with mouse movement or window redraws. > > Most likely you won't be experiencing this when connecting the edirol to > the presonus device. The only way to find out is to try it. Be sure to > use balanced cables. > Cool, thanks. > > > >He runs at 96Khz, IIRC. I dunno if that will make the noise better, > >or worse. It'd be nice to go S/PDIF out, but I don't know if that'll > >work either, if the sample rates don't match. > It only works if the samplerates are the same and the two cards are > sync'ed. Analog will be easier. Again, thanks. - -ken -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.1 (GNU/Linux) iD8DBQFGS5WLe8HF+6xeOIcRAnypAJsFTm9lxsNP4vmeOHraf/bZzkIy2QCglrGk VhvQHcpqUcvIrrORG52VfIc= =Usq0 -----END PGP SIGNATURE----- _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo.cgi/linux-audio-user
