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SPDIF Recording Level

Discussion in 'Recording' started by aireq, Jan 1, 2008.

  1. aireq

    aireq Guest

    I've been trying to go through and record all my vinyl to wave files. I have a Technics 1200 M3D running into a Tascam X-9 DJ mixer. I recently purchased the Tascam because I have decided to switch from DJing vinyl to CDs and it has two SPDIF inputs and one SPDIF Output. My computer is on the otherside of the room so I wanted a digital out to minimize the degregration of signal between the DJ mixer and my sound card (an M Audio 2496).

    I'm having a problem getting my levels to make any sense. Before I record any record I adjust the gain on the DJ mixer so that the level seen by the soundcard is just bellow but never above 0 db.However, to get the sound card to show 0 db I have to increase the level of the DJ mixer so high that the meter on the mixer goes off the scale which tops out at +14 db.

    To further verify this I created a CD with pure white noise at 0 db. I then played this through the SPDIF out on my CDJ into the SPDIF in on the DJ mixer and then to the sound card. Again I had to increase the gain on the DJ mixer so high that it's meter went off the scale to get the level at the soundcard to 0 db.

    To verify that there wasn't some recording level setting in my sound card that I was missing I played a cd with 0 db, -6db, and -12 db samples of white noise directly from the SPDIF out on my CD player into my sound card. The sound card meter showed exactly those levels so I know the issue is with the mixer.

    Any idea why the DJ mixer would be showing such high levels?

  2. Space

    Space Distinguished Member

    Jun 26, 2007
    The turntable output signal most likely needs a boost before the input of the mixer.

    http://www.channld.com/Connecting a Turntable R1.pdf
  3. bent

    bent No Bad Vibes! Well-Known Member

    Oct 26, 2007
    Cocoa, FL
    I don't have an X9 but have you tried switching the coax master between pre / post (sounds like it might be set to pre-fader)?

    From Tascam.com: The X9 has a coaxial digital master output with pre/post master selection in the menu...

    Edit> Here's the manual.

    Read page 10.

    It appears from the manual that they consider 7 on the master to be unity gain, therefore, I'd set the master to 7 and adjust the input gain until your signal through the soundcard is at unity.

    Doesn't really explain the CD SPDIF level though...
    Perhaps a factory reset is in order?
  4. Boswell

    Boswell Distinguished Moderator Resource Member

    Apr 19, 2006
    Home Page:
    I think this is the old story of what is meant by "0dB" in a digital context.

    The X9 appears to have 0dB arbitrarily defined as -14dBFS, although the manual is not clear on this. The M-Audio 2496 almost certainly has 0dB defined as digital full scale. So you would expect a 14dB difference between the way the two different pieces of gear display their respective levels. If you simply ignore the markings on the X9 level meters (or subtract 14 from them so 0dB is at the top), you should get equivalence between the two. It's the level received by the 2496 that's the important one, and you should adjust the level controls on the X9 until you get peaks that don't clip as seen (across the room) by the 2496.

    By the way, transmitting S/PDIF over more than a couple of metres of cable without digital errors requires care and thought.

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