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96k on a new mac pro

Discussion in 'Recording' started by cheeburger, Feb 4, 2011.

  1. cheeburger

    cheeburger Active Member

    I'm attempting to connect my apogee rosetta ad to my mac pro quad via the Toslink
    (S/PIDF also called lightpipe) port on the back of the mac. Everything works fine until I choose 96k on the mac audio midi setup. It keeps bouncing back to 48k. Nax and apofee gave no solution.
     
  2. Big K

    Big K Well-Known Member

    Hello cheeburger

    Welcome to our Recording.org forum!

    I fear, TOS link / lightpipe/ ADAT can only do 44,1 kHz and 48 kHz. You probably need 2 opticals for running a multiplexed signal of 96 kHz.
    If you don't have 2 optical outs and ins you might want to use AES/EBU connection or a firewire / USB frontend, where you don't need to run opticals into the mac.
     
  3. dvdhawk

    dvdhawk Well-Known Member

    Go to your Apple Menu and choose "About This Mac", select the "More Info..." button. Highlight "Audio (Built In)"

    You'll probably see that your Mac's digital format audio sample rates for PCM 16-bit, PCM 24-bit, and AC3 16-bit are limited to 32kHz, 44.1 kHz, and 48kHz.

    Also, all Toslink inputs are not created equal either. Unless the Toslink/Lightpipe is specifically ADAT or SMUX protocol it's probably limited to 2 channels. So obviously, you have to make sure your channel count matches.

    I think you're going to need a 3rd party card to interface at higher sample rates. I'm surprised the Apogee didn't include the PCI card.
     
  4. Boswell

    Boswell Moderator Distinguished Member

    Which Rosetta is this? Are you sure you mean S/PDIF protocols and not ADAT?

    I regularly use S/PDIF protocols at 24-bit/96KHz both optical and coax. It's important to check that your drivers are set up to recognise and lock to incoming 96KHz data.

    ADAT data is essentially 8-channel 48KHz (max), which can be multiplexed using S/Mux protocols to provide 4 channels at 96KHz over one lightpipe. Although the mode bits in the data can in principle tell this is S/Mux, in practice it is usually necessary to set both ends up to the same data type.
     
  5. cheeburger

    cheeburger Active Member

    rosetta ad on a mac pro

    I'm connecting straight to the mac with the lightpipe. The rosetta is set to S/PIDF rather than adat. The rosetta only has xlr inputs and only one lightpipe output. It does have a TDIF, a SPIDF , and an AES output but I'm trying not to buy another piece of equipmen that's only function would be to provide access to the mac. The audio midi setup utility in the mac has 96k as a choice but bounces back to 48k after a second when the rosetta us swt to 96k. If what I'm trying is not possible if someone can suggest an inexpensive converter to preserve the 96k, that would be great.
     
  6. cheeburger

    cheeburger Active Member

    The mac is running snow leopard. The specifics say it will handle 96k through the TOSLINK optical. I'm using an older ADAT lightpipe cable. Any chance the cable only goes to 48k? It fits perfect. The manual also says 8 channels of 192k is available through the mini display ports which I don't recognize the format of.
     
  7. Boswell

    Boswell Moderator Distinguished Member

    You still didn't give the model number of the Rosetta, but from what you say, I'm assuming this is the 200 and not the 800. What you want to do should be possible, but the Rosetta is quite a flexible unit with some confusing panel indicators, and it's necessary to get the sample rate and optical output format set right. Since the Rosetta has built-in sample-rate conversion, the optical output rate is not necessarily the same as the ADC sample rate. A long push on Sample Rate should show S/PDIF optical format.

    The symptom of the MAC resetting to 48KHz points either to the Rosetta not correctly setting to 96K S/PDIF as its optical output format or (possibly) your Toslink lightpipe attenuating too highly at the double bit rate.

    If the rates seem to be correct, you could try outputtting a 96K S/PDIF optical data stream from the Mac and taking that into the Rosetta via one lightpipe, syncing the Rosetta to the incoming clock, and then seeing whether the Mac will recognise the outgoing bit rate from the Rosetta on the second lightpipe as 96K.
     
  8. TheJackAttack

    TheJackAttack Distinguished Member

    The cable doesn't know any difference between sample rates. The cable could be compromised however and not pass enough data to sync at 96k.
     

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