PT 888/24 Alignment...Screw Loose!

Discussion in 'rec.audio.pro' started by rickymix, Aug 20, 2003.

  1. rickymix

    rickymix Guest

    Hi guys!
    Once again, I've discovered I'm an idiot, although I don't know
    why that continues to suprise me each time. :>)
    Much to my delight, I finally figured out how to patch analog
    outboard gear into my Protools (v 5.01) by using the channel Insert
    I/Os. Unfortunately, the signal comes back into Protools boosted a
    lot, sounds like at least 10 dbs, no matter which API EQ I patch into.
    I suspect the 8 Input or 8 Output screws on the front panel of my
    888/24 Interface are not properly aligned. I've done the PT software
    alignment and I'm pretty confident that's right; it's got to be those
    screws. I remember once setting that up with someone years ago, but I
    bet we messed it up and it's been wrong ever since. It would explain
    various level problems I've had since.
    So I've searched the Manual and Googled without success.
    Hopefully someone here can help me out, either by pointing me to where
    it is in the manual or describing the proper proceedure for aligning
    those dang screws. For reference signal, I've got an API 575
    Oscillator, although I have no idea what "0" on that thing means in
    reference to the rest of the world. I've also got a DAT with tones at
    "-20 dbs" from the Video-Post facility where I work. The only analog
    meters I have are the stereo buss meters on my Speck SSM console, and
    I really am not sure what "0" means on them either. I'm flying blind
    here.
    Thanks as always for sharing your knowledge and expertise.
    Cheers, Rick Novak.
  2. snovak2@earthlink.net (rickymix) wrote in message news:<5b0ae9b9.0308200124.1387c687@posting.google.com>...

    > So I've searched the Manual and Googled without success.
    > Hopefully someone here can help me out, either by pointing me to where
    > it is in the manual or describing the proper proceedure for aligning
    > those dang screws. For reference signal, I've got an API 575
    > Oscillator, although I have no idea what "0" on that thing means in
    > reference to the rest of the world. I've also got a DAT with tones at
    > "-20 dbs" from the Video-Post facility where I work. The only analog
    > meters I have are the stereo buss meters on my Speck SSM console, and
    > I really am not sure what "0" means on them either. I'm flying blind
    > here.
    > Thanks as always for sharing your knowledge and expertise.
    > Cheers, Rick Novak.


    Rick, I'll try to get this in a few simple steps - but first, you must
    have a known reference level for +4dBu. Using -20dBFS off a DAT
    doesn't tell you much, because you're not certain what the DAT
    machine's analog outs are referenced to. So, track down a known +4dBu
    1k tone and do the following:

    1) Open up a session, create and record-arm an audio track set for
    input 1 from the 888, and put PT in "calibration mode" under the
    Operations menu

    2) In Setups->Preferences, set your prefered reference level (i.e.
    what digital level to you want to equal +4dBu at the analog ins/outs?
    -16dBFS? -18? -20?)

    3) Plug your known +4dBu 1k tone into input 1 on your 888 and you'll
    see the meter react on your armed audio track, as well as a flickering
    readout of the level

    4a) Adjust the input gain screw on the front of the 888 until your
    audio track reads the level you chose in step 2.

    4b) Repeat step 4a for all inputs by switching the input on your audio
    track to match the input your tone is plugged into


    Now that your inputs are calibrated, you can use one of them to help
    calibrate the outputs:

    1) Create an Aux track in your session and put a Signal Generator
    plugin on it, set to 1000Hz and your reference level from step 2 above

    2) Set the Aux output to whichever output you're going to be
    calibrating starting with Output 1 (make sure it's mono, NOT a stereo
    pair)

    3) Plug output 1 into into input 1 of the 888, keeping your audio
    track's input set to Input 1

    4a) Adjust the output 1 gain screw on the 888 until your audio track
    reads your chosen reference level

    4b) Repeat for every ouput by patching the 888 output 2 to input 1 and
    changing the Aux track output to Output 2, and so on.

    The main issue, however, is choosing which reference level you want to
    go with. That depends on what kind of gear you frequently interface
    with and what kind of headroom you require for your work. For
    instance, my post house is referenced to -20dBFS = +4dBu = 0VU, but
    some mastering houses out there may be referenced to -12dBFS = +4dBu.

    -Chris
  3. lyndholmproject@hotmail.com (Chris Coleman) wrote in message news:<fa9bc045.0308200818.660f9996@posting.google.com>...
    > snovak2@earthlink.net (rickymix) wrote in message news:<5b0ae9b9.0308200124.1387c687@posting.google.com>...
    >
    > > So I've searched the Manual and Googled without success.
    > > Hopefully someone here can help me out, either by pointing me to where
    > > it is in the manual or describing the proper proceedure for aligning
    > > those dang screws. For reference signal, I've got an API 575
    > > Oscillator, although I have no idea what "0" on that thing means in
    > > reference to the rest of the world. I've also got a DAT with tones at
    > > "-20 dbs" from the Video-Post facility where I work. The only analog
    > > meters I have are the stereo buss meters on my Speck SSM console, and
    > > I really am not sure what "0" means on them either. I'm flying blind
    > > here.
    > > Thanks as always for sharing your knowledge and expertise.
    > > Cheers, Rick Novak.

    >
    > Rick, I'll try to get this in a few simple steps - but first, you must
    > have a known reference level for +4dBu. Using -20dBFS off a DAT
    > doesn't tell you much, because you're not certain what the DAT
    > machine's analog outs are referenced to. So, track down a known +4dBu
    > 1k tone and do the following:
    >



    Rick,

    Also, when you setup your calibration session, set the Audio track to
    No Output, otherwise you'll get feedback when you start calibrating
    your outputs. For more great into on reference levels and what you
    use, check out Bob Katz' www.digido.com
  4. rickymix

    rickymix Guest

    Thanks for the scoop, Chris! I wound up using the meters on my DAT
    machine to determine roughly where -18 on my API oscillator was. (-3
    on the API.) Then I set the inputs of the 888 with the API tone and
    the outputs using the calibration tool. Not scientifically accurate,
    but probably within a db of being right, and all the channels are
    evenly matched to each other. They weren't more than .2 dbs off in
    the first place, it turns out.
    The inserts are returning at unity now too. I think the reason
    they were coming back so hot at first was due to a patch bay normal
    returning to an open fader on my console as well as hearing the signal
    in Protools. Operator error, as usual! Doh!!
    Thanks again, Rick.

Share This Page