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Is 48K the top rate for ADAT Lightpipe?

Discussion in 'Pro Audio Equipment' started by jeronimo, Sep 7, 2001.

  1. jeronimo

    jeronimo Guest

    Can anyone answer me this? If yes, what kind of "protocol" is used for 96K on those MOTU Interfaces, those RME Multiface, and all the 96K converters around?
     
  2. Rader Ranch

    Rader Ranch Guest

    i'd love to know what lightpipe is all about too. on that RME site they mention something to the effect of 'thru our proprietary methods, we are able to send 1 ch. of 96k down the space of 2 ch. of 48k', 48k being the normal limit of ADAT lightpipe apparently. and then you have 2ch 'spdif' lightpipe connections on gear as well. i mean, isn't plastic plastic? can't it just handle x bandwidth and that's the end of it?

    and here's an xtra stupid question...can one buy the cable and connectors and make 'em themselves? they certainly look cheap enough...
     
  3. try2break

    try2break Guest

    What RME, and every other manufacturer of converters that send 96k over Lightpipe do is split the 96k signal in half and uses 2 channels of the lightpipe protocol to send 1 channel. It is basically double speed. So you only get 4 channels. You can also double it again and get 2 channel 192k. I'm not sure if anyone is doing that yet. I guess it will be possible to do 1 channel of 384k but that is years in the future when everybody is complaining about the top end harshness of "only" 192k.

    > and then you have 2ch 'spdif' lightpipe
    > connections on gear as well

    What? Lightpipe(TM) is ADAT brand 8 channel 24 bit/48k over Toslink optical cable. SP/DIF is the Sony/Philips 2 channel 24bit/48k protocol. It uses 75 ohm rca or Toslink plastic fiber.

    >isn't plastic plastic? can't it just handle
    > x bandwidth and that's the end of it?

    But digital protocols are what is sent over the plastic. SP/DIF and Lightpipe(TM) use different "languages" even though it is the same physical media.


    >and here's an xtra stupid question...can one
    > buy the cable and connectors and make 'em
    > themselves? they certainly look cheap enough...

    Give it a try and then let me know the new curse words you make up when you hear clicks and pops in your audio. How were you supposing to connect the cable to the connector? Super glue?
     
  4. jeronimo

    jeronimo Guest

    Ok, I got it now! Thanks try2break!
     
  5. Rader Ranch

    Rader Ranch Guest

    Originally posted by try2break:
    Lightpipe(TM) is ADAT brand 8 channel 24 bit/48k over Toslink optical cable. SP/DIF is the Sony/Philips 2 channel 24bit/48k protocol. It uses 75 ohm rca or Toslink plastic fiber.

    exactly my point...toslink/toslink. it's just a bit confusing why certain boxes would waste 4 toslink connectors just to get 8 ch.'s of spdif down 4 lightpipes when one of the cables could easily handle all the data. i guess it's the concept of 2ch 24/48 optical itself that seems a waste.

    Originally posted by try2break:
    How were you supposing to connect the cable to the connector? Super glue?

    how the ^#$% would i know? like i said, the factory ones i use certainly look cheap, and are hardly what i'd call robust.the whole plastic toslink connection in general seems pretty damn cheesy considering the accurate clocking we all want to achieve.
     
  6. recordista

    recordista Active Member

    Joined:
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    Originally posted by Rader Ranch:
    it's just a bit confusing why certain boxes would waste 4 toslink connectors just to get 8 ch.'s of spdif down 4 lightpipes when one of the cables could easily handle all the data.

    But the standard (at this point) only defines rates up to 48kHz (maybe 50 if I recall) so if you stuffed 96kHz samples in it there would be nothing else that could read it. Something akin to the AES/EBU single-wire standard would accomodate this but until Alesis defines it, anyone implementing it would run a big risk.
     
  7. try2break

    try2break Guest

    Is bit split not cross manufacturer compatible? Say, if you used Apogee converters at 4 channel 96k over Lightpipe to an RME Hammerfall, it wouldn't work?
     

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