SPDIF

This topic contains 7 replies, has 7 voices, and was last updated by Profile photo of tk2k tk2k 8 years, 3 months ago.

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  • #22741
    Profile photo of brandonhw
    brandonhw
    Participant

    Does anyone use S/PDIF on their iLive? I have posted before about this, but have yet to find any suitable solution. I’ve found numerous threads on other, non-related forums about volume levels coming from S/PDIF, which all mimic the problem I’m having, but they do not have any solutions.

    I am trying to use a digital output from my T-112 surface. Here’s the problems, and what I’ve done to check it:

    1. When I connect any of my equipment to the output, the volume level received is very low. I have no way of boosting it much, although my CD-recorder does have a means of increasing the recorded volume by up to 18 dB, which seems to help quite a bit. My computer has no such adjustments, so it’s useless. I get enough volume to hear, but not much to be useful for my streaming application.

    2. To test the output(s), I simply loop them back to the S/PDIF input on the board, and send pink noise through. It works fine in this case.

    3. To test my outboard equipment, I repeat the process with a Pink Noise CD, recorded at 0 dB (on the scale of the CD recorder), and send it to my computer (works fine), and to the iLive (way too loud, but I can turn the gain all the way down and it is usable).

    So the only problems seem to lie in the interaction between the iLive and the other components. It doesn’t seem defective, just that it is not the same signal specs on the wire. Does this make sense?

    I’ve been told not to try to interpret dB scales, and I’m trying to ignore the fact that O dB pink noise on the board won’t produce a 0 dB scale reading on any other equipment (it’s more like -40 dB), but even the perceived volume and adjustability is just totally off.

    Has anyone else experienced anything like this? Or does anyone have time to try with some other piece of hardware?

    I’ve tried with a couple of consumer CD recorders, a Tascam professional model, and an M-Audio USB interface, all with the same results.

    I’d love to hear if there are any similar stories, or equipment combinations that will work.

    I’ve thought about adapting to AES/EBU to check that out, but I don’t know if that would make any difference, since they’re supposed to be almost identical standards.

    Thanks!

    Brandon

    #28043
    Profile photo of Stealth
    Stealth
    Moderator

    Hi Brandon

    we are not aware of any issues with the digital output of iLive systems

    It is possible dB scaling differences is what you are seeing.

    iLive uses dBu metering where as alot of digital recording/playback equipment displays metering in dBFS.

    if a signal is 0dBu on the iLive the signal viewed on the external equipment will be -18 dBFS. This would explain what looks like a drop in signal level.

    quote:


    Wikipedia
    EBU R68 is used in most European countries, specifying +18 dBu at 0 dBFS


    http://en.wikipedia.org/wiki/DBFS

    Regards
    Sam A&H

    #28045
    Profile photo of Mr-B
    Mr-B
    Participant

    Vaguely remember this may have come from an old BBC spec for setting up early digital recorders, you send PPM 4 (0dB) from the desk and set to -18 on the recorder that way you don’t overload the recorder.
    Could be wrong memory fading with the years for sure.

    #28053
    Profile photo of brandonhw
    brandonhw
    Participant

    That’s pretty much what I’ve gathered. It doesn’t help me get a usable digital signal, bit it makes sense. Any suggestions other than falling back on analog?

    If I could find a pc interface that uses this standard, then I could make do with it.

    Thanks all.

    BTW.. had my first lockup today. System froze shortly after power up when I tried to change the volume of a slider. The only thing that I think might have caused it was that there were accidentally two of the same channels at different locations on the board.

    Brandon Walls
    Sound Engineer
    First United Methodist Church
    Cookeville, TN

    #28057
    Profile photo of kentlowt
    kentlowt
    Participant

    That should not cause a lockup I have a few faders patched to the same input never caused an issue. Every time I have had a lock up it has been network related. IP conflicts etc. I would look there first.

    112T/IDR48/IDR16

    #28063
    Profile photo of FortMacTech
    FortMacTech
    Participant

    We use the SPDIF out into a Tascam flash recorder and have no issues. We feed the outs from an Aux so we can output whatever level of signal we need to keep the recorder happy. It also gives us an opportunity to mix our recording signal since we are doing live church services.

    T112 iDR32 M-MMO

    #33347
    Profile photo of jcintas
    jcintas
    Participant

    I am having the same issue on a T-112 SPDIF out to a PC for recording mono track recordings of our church service and sermon. I also see the issue of the T-112 sending out a signal at 0db according to its meters from a matrix out and on the computer side I see -18db or less. This causes us to have to go through a digital normalize process after every recording to get the levels back up to audible levels for recording distribution.

    Any work arounds?

    A&H give us an option to switch the SPDIF output mode from dBu to dBFS, especially since Sam from A&H says most recording devices are dBFS.

    — Jerry
    T112/iDR 64/MixPad

    #33348
    Profile photo of tk2k
    tk2k
    Participant

    quote:


    Originally posted by jcintas

    I am having the same issue on a T-112 SPDIF out to a PC for recording mono track recordings of our church service and sermon. I also see the issue of the T-112 sending out a signal at 0db according to its meters from a matrix out and on the computer side I see -18db or less. This causes us to have to go through a digital normalize process after every recording to get the levels back up to audible levels for recording distribution.

    Any work arounds?

    A&H give us an option to switch the SPDIF output mode from dBu to dBFS, especially since Sam from A&H says most recording devices are dBFS.

    — Jerry
    T112/iDR 64/MixPad


    I hate to say ‘why does it matter?’ but why does it matter? if its’ digital all through the chain it shouldn’t make any difference other than visual?

    The -18db is actually very smart, that headroom is extremely useful in multitrack settings so you don’t overload a bus.

    p.s. I often user a external headphone amp for cans, and I have not had an issue (uses SPDIF)

    iDR-48, T-112, Mixpad
    College

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