Paolo Saggese wrote: > On Thursday 22 November 2007 15:25, you wrote: >> > This is a valid wish, isn't it? And at least the >> > M-Audio Audiphile cards can sync themselves to the S/PDIF In clock. >> >> They can, but the word clock is used only as a sample clock. It will >> not reduce the amount of jitter of the card's S/PDIF output. > > that's not a concern! > > Let' try to explain it better: it's all about avoiding the use > of the SPDIF reconstructed clock altogether (on the DAC side). The S/PDIF standard specifies that the clock must be reconstructed from the signal itself. > If I can "slave" the SPDIF clock coming into the external DAC to > the same DAC local clock, I can simply ignore the incoming SPDIF > clock and just use the local one without any need for reclocking, > PLLs, etc! Yes, _if_ you can. <http://www.audiocraftersguild.com/AandE/npt.on.jitter2.htm> says: | A few companies which make both transports and external DACs have | implemented schemes in which the S/PDIF signal is supplemented with a | second line carrying the master clock back from the external DAC to | the transport. In this way the DAC's crystal becomes the master rather | than the transport and the problems of recovering a spectrally pure | clock are eliminated. No standards for this type of implementation | exist. In reference #4 Dr. Hawksford calls for the clock signal to be | transmitted on a second S/PDIF line, I know of no actual product which | implements this scheme. Sony (in one product) and Arcam send the | actual clock, Linn argues this leads to RFI problems and so they send | a DC servo voltage which controls a VCOX in the transport. So it seems you wouldn't be able to find a sound card that does what you want. If all your audio data comes from the PC anyway, you might want to drop S/PDIF and use a sound card with a break-out box. The I2S bus used to control the DACs in those devices has a separate master clock line. Regards, Clemens ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Alsa-user mailing list Alsa-user@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-user
