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s/pdif bit rate question

Discussion in 'Recording' started by RitaRose, May 3, 2007.

  1. RitaRose

    RitaRose Guest


    I've got an m-audio fast track pro connected to pro tools and I'm thinking of recording drums using 2 mics into the XLR inputs and utilizing the 2 channel S/PDIF input. I understand I can do this even though the bit rate and sample rate will go from 24bit 96khz to 16bit 48khz. For the extra 2 mic I'm happy to compromise. What I thought I would do is buy 2 samson C-valve pre amps which I can connect to eachother to create a 2 channel S/PDIF input (I've checked the manual and it says I can do that). What I wanted to know was whether there would be a problem with me connecting the 24bit 48khz samson S/PDIF out to the 16bit 48Khz m-audio S/PDIF in. If so how can I get around? can I?

    Can anyone help?

  2. Boswell

    Boswell Moderator Distinguished Member

    You should be able to use the Fast Track Pro at 24-bit 48KHz for 4 inputs (two XLR and two S/PDIF channels) and two outputs concurrently. You would not need to drop to 16-bit operation unless you needed four outputs at the same time.

    The M-Audio manual seems to gloss over the need to synchronise to the S/PDIF incoming clock, but I assume they have done their job and that function is automatic.
  3. RitaRose

    RitaRose Guest

    hm.. I'm sorry I'm a bit of a newbie with all this. What does synchronize to an incoming S/PDIF clock mean. Will this setup not work? I read the bit about the 4 inputs at 24 bit if I only have 2 outputs. I seem to have missed that before.

  4. Boswell

    Boswell Moderator Distinguished Member

    It should work OK.

    When two devices communicate digitally, the receiving device has to have a way of locking its speed to the transmitting device so that data is not lost somewhere in the void between them. In some communication schemes, there is a connection for data and another for the clock (the timekeeping signal). In S/PDIF, there is only one connection that carries both the data and enough information for the receiver to reconstruct a clock. However, the receiver usually has to be told to do this rather than to use its own internal clock. On a quick look, there didn't seem to be anywhere in the M-Audio literature a way of instructing the receiver to take its clock from the S/PDIF data stream as well as just enabling the S/PDIF data input. However, M-Audio has a pretty good reputation, so I would be surprised if this didn't happen automatically.
  5. RitaRose

    RitaRose Guest


    well I'll buy one and give it a go and if it works then I'll buy another one.. else it will go on ebay..

    Thank so very much..

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