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Thread: Blown out audio

  1. #1
    Registered User bbailey's Avatar
    Join Date
    Jan 2009
    Location
    Odessa, Texas
    Posts
    499

    Blown out audio

    A few weeks back I had a strange complication happen while setting up for a four camera shoot with my 860.

    As I was hooking up at the venu the sound guy handed me a cable with an XLR-M and said he was already giving me a tone signal at line level for me to set up with. I went ahead and made the connection to my 860. After everything was connected I fired up the trailer and launched my 860. When it finished booting up I could see I had all four cameras and that an audio signal was present. When I turned on the sound system I noticed the audio, although it appeared to be at the correct level on the VUs, sounded extremely distorted. Not long afterwards the sound guy cut the tone and started testing the mics. Again, the level appeared correct but sounded terribly distorted. I lowered the volume of the audio channel but the distortion was there even at a low volume. I double checked my setting but I had the input set for line level.

    I went inside and found the audio guy and told him I was getting distortion. He said , "It's not coming from me!"

    He was using a patch panel within the facility to get a cable out to my trailer and I suspected it was a bad cable. Turns out he had a little Q-Box which had 1/4" inputs, RCA inputs, XLR inputs, a speaker and small amp built in. He said I should try listening to the Q-Box with his cable and see if the distortion was at the Q-Box proving his cable as being bad and I could trace it backward into the facility.

    When I tested the signal with his cable right immediately before my 860, I found the signal to be clean. When I plugged into my 860 I had the bad distortion. Realizing it was me who had the problem I thought I was done for. I was starting to think about how I could do some sort of work around. I recorded to an AJA KI PRO for ease of editing back at the studio with my FCP7. I saw audio level on the KI PRO's VU. I checked it's signal with some ear buds and discovered that the sound was clean. I was sending HD-SDI to the KI PRO with embedded audio from the 860's SDI output.

    Now I was really confused. I actually considered leaving everything alone and just going with it since my recorder's audio was clean. But I also record with the Tricaster's internal media drive as a backup and decided not addressing the problem right then might be a mistake. I decided the first thing I should try is to simply shut down the Tricaster and do a fresh reboot. Well... that did the trick. Audio was clean everywhere. Thank goodness for the Q-Box. I don't know if I'd have considered a reboot so quickly without being sure the cable wasn't the problem. I suppose that should be the first thing one should try if one's TriCaster doesn't perform normally once one boots up the first time. I wonder if anyone else has had this happen to them?

    I haven't tried booting up with tone already running to see if I can duplicate the problem but I suspect that it might occur again.
    Tricaster 860 and CS
    3Play 330 and CS

    Sony PMW-EX3
    5-Sony HXR-NX5
    Sony Z1-U
    FCP7 & FCPX NLEs
    2-AJA KI PROs
    BM-ATEM 1ME Production Studio
    BM-HyperDeck Shuttle recorder

  2. #2
    Registered User
    Join Date
    Oct 2012
    Location
    Munich, Germany
    Posts
    80
    Hello,

    i only want to jump in for a comment on getting external audio from someone (where you dont have fully own controll over the used equipment and cabling) to feed it into a tricaster/your equipment.

    In such case i would highly suggest to use a "isolation device" in the audio lines, something like the ART DTI ( http://artproaudio.com/artcessories/...s/product/dti/ ). Such a Device is very cheap (between 50 to 300 USD) compared with what you might risk on your side.

    You never know what could be or gets wrong on the other end of the cable. This could be a different power phase or a simple missconnected plug.
    It might also save you a lot of hassles with hummings.

    Professional audio guys mikght have such devices connected by default, inline with the cable to you or have one prepared, but in case not, you should have your own available.

    best regards,
    Walter


    PS:
    Such audio isolators might always introduce some kind of distortion to a audio signal.
    So in fact there might be quality differences comparing different issolation devices. The quality mainly depends on the used audio transformers build into such device.
    For what we do (non professional) sport the device from ART worked very good. Without doing measuments i am not able the hear any difference between simply line or line with isolator.
    TC8000 / TW850
    Cables: Belden 1694/Canara Connectors
    Cams: Sony PWM-EX3, Sony HDR-CX430/BMD HDMI2SDI

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