On Fri, May 28, 2010 at 05:05:19PM +0200, Robin Gareus wrote: > Well, interpreting an 'experiment' that one has not conducted > him/herself without knowing _all_ parameters of the setup is not > something to encourage doing..
> Did you use symmetric (XLR) connections? Where possible, yes. Note that we are seeing a *modulation* effect, the level of the spurious signals is proportional to the wanted signal. It's not additive. > Are the sample-rate settings of both cards identical? Shouldn't matter, as the connection is via an analog signal. > what was the physical distance between the devices > (cross-talk)? It's absolutely not crosstalk. > Was there any ground-lift equipment (built-in?) in place > or maybe you simply forgot to switch off phantom-power? All those would create additive effects, which is not what we see. Phantom power, where available, was off. Card X has both line and mic inputs, all show the same result. Mic inputs are driven via a balanced passive attenuator with an output impedance of 50 ohm. > Anyway, good that you've labeled it 'quiz'; so here's my guess: > > You're encountering reflections (or even standing-waves) in the cable. > (did you uncoil it? or was it a very short one?) > Did you repeat the measurement? using different cables for example. No differnece seen between a cable of 3 m and on of 18 m. This will answer most other posters, except Chris: > Why 1015 Hz ? To clearly separate the signal from any 50 Hz harmonics. One more hint: card X is a very high end one. It should be 'perfect', or at least much better than card A. Ciao, -- FA O tu, che porte, correndo si ? E guerra e morte ! _______________________________________________ Linux-audio-dev mailing list [email protected] http://lists.linuxaudio.org/listinfo/linux-audio-dev
