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  4. OT: Word clock troubles

  • OT: Word clock troubles

    P
    P
    Hi friends,

    Can anyone of you maybe give me a good link on the web for a detailed "howto" for hooking up 4 PC's via word clock?

    I can't find anything on max cable lengths etc.

    This is a short description of my puzzle:

    In my former office/studio room I had only my DAW in my working room and 3 Giga PC's in a nearby hallway. Word clock cable of 10 meters to the Giga PC's, daisy chained. Please note: wrong impedance (50 instead of 75 ohms) and no terminators. Output via 3 Adat cables back to the DAW, into Logic 5.5.

    Absolutely no syncing problems, in spite of the incorrect impedance...

    Now, in my new appartment, the cable length is 18 meters, instead of 10 and I just can't get my stuff working without a LOT of clicks and often constant noise.

    The DAW HDSP 9652 dialog politely tells me "Sync" for all 3 Giga's, but my mixer and speakers tell me a different story.

    I started (again) with an incorrect impedance cable of 50 Ohm. Problems. So I replaced that one with a very high quality cable of 75 Ohms. Tried every order of daisy chaining, but there is always at least on PC giving lots of noise, and the others intermittent clicks...

    Do I need to hire some technician with an oscilloscope and "really" good cables?

    This is driving me nuts, replaced cables several times (a lot of work, because they are nicely hidden and run to a closet 10 meters from my desk... Applied terminators, no terminators, no difference.

    My audio cards are:
    "Elfman": RME HDSP 9652 (DAW)
    "Zimmer": RME Digi96/8
    "Silvestri": RME Hammerfall 9652
    "Williams": RME Hammerfall 9652

    Pretty good cards, in my experience.

    PC's are all Athlon's, 3000, 2600, 2200 and 1800.

    Would it be possible that there is an interaction between the WC pulses and the length of my Adat cables? I heard that 18 meters (custom made for me) is quite long for Adat.

    Any comment is more than welcome!

    TIA,
  • DietzD
    VSL Team
    DietzD
    Hi Peter -

    18 m for lightpipe is pretty long, but shouldn't be the main problem. For a medium-sized setup like yours I would strongly suggest a "hose clock", read: a dedicated clock-generator like a Rosendahl "NanoSync" and sync all your equipment in a "star"-setup from there on behalf of dedicated wordclock cables. I'm positive that you will get rid of your issues and will most likely improve your sound, too, as an added value.

    HTH,
    /Dietz - Vienna Symphonic Library
  • N
    N
    It's never a good idea to use the clock embedded in lightpipe, but it's especially bad over long distances; if you're using lightpipe it's always a good idea to run a wire (S/PDIF, AES, or word clock) for clock.

    I'm also not sure what the maximum for lightpipe is, but 18 meters sounds very, very long. Without wanting to make myself sound like a professional lightpipeologist, I do know that the issue with it is diffraction, and the biggest problem area is at the connectors. So you should definitly make sure the pipes are straight and that the connections are solid.

    Usually people convert the signal to glass fibre when running it long distances in live applications. Hosa makes a box that does this, but I'm not sure how expensive it is.

    What Dietz says is going to be the solution with the lowest jitter, but if you didn't want to invest in a box like the Rosendahl right away, you could just use S/PDIF (over 75 Ohm video cable, which isn't expensive) and then pick up an inexpensive video distribution amplifier on ebay to give yourself more S/PDIFs.
  • P
    P
    Thanks Dietz and Batz!