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Audio Patch panel in video production studio

Discussion in 'Pro Audio Equipment' started by videodok, Jul 19, 2007.

  1. videodok

    videodok Guest

    Last week I came in a studio which uses a mackie 1604. It is hooked up to a patch panel which links it to the different recorders and computers. Everything is connected with TRS jacks. The patch panel is a stero patch panel. But i saw they only used Mono-jacks to patch the signal. A lot of equipment uses balanced signals( mackie 1604, dvcpro recorder, edititing stations end so on)
    In my opinion you should always patch with TRS jacks so you have the benefit of the balanced signal. Some equipment don't have balanced outputs but still I would use a TRS jack.

    What is you opinion? Am I totaly wrong on this? And what happens if you pacth a balanced signal with a mono-jack what consequences will this have?

    The studio is planning to reorganise their setup, I want to help, but I need to know why the guys who installed it years ago, did it like this and what I should do for the new setup
     
  2. Boswell

    Boswell Moderator Distinguished Member

    I assume from your description that the equipment is wired balanced and unbalanced (as appropriate) to the rear of the balanced patch panel, but that the studio is using TS (unbalanced) patch leads.

    Consider the 4 cases:

    (1) unbalanced out to unbalanced in: TS patch is OK

    (2) unbalanced out to balanced in: TS patch is usually OK, as the TS jack sleeve correctly grounds the negative (cold) input of the balanced gear.

    (3) balanced out to unbalanced in: TS patch will short the negative (cold) output of the driving gear to ground. For electronic outputs, this may or may not cause problems (excessive dissipation in the output stages, harmonic distortion etc), and it will usually result in a 6dB signal loss. Fully floating transformer outputs should not cause a problem other than loss of noise immuniity. Centre-tapped transformer outputs with the centre tap grounded will not work at all.

    (4) balanced out to balanced in: same as (3)

    In all cases, the noise immunity of balanced signals will be lost.

    In summary, the effect of using TS patch leads depends on the gear being patched. They may get away with it, they may wonder why they need an extra 6dB of gain sometimes, but they may not notice that some signals need the extra gain and have added distortion.

    If the panel to equipment wiring is all balanced, then it's a simple matter to buy a bunch of balanced patch leads and you're in business.

    As a side issue, I hope the microphone inputs are not patched with TS leads!
     
  3. videodok

    videodok Guest

    Boswell, thanks for your answer. First of all isn't it better to always use TRS patches in this situation, not having to check if you are using a balanced or unbalanced source. The unbalanced source are automaticly correctly wired to the patch.
    Is there any good reason to patch with TS patches? If not I'll make TRS cables myself and throw away the TS jacks.

    Mic's are connected directly to the mixer I asume you are asking
    this because of the phantom power for mic's?
     
  4. Boswell

    Boswell Moderator Distinguished Member

    Some people say you get better grounding with TS jacks, but I would think there's no difference provided you buy high-quality components. One advantage of buying rather than making patch leads is that you can easily get a selection of colours. I find colour-coding the various patches quite useful when re-patching in a hurry.
    Yes, mainly, but also because microphone signals are a thousand times smaller than line-level signals they are much more easily contaminated by noise due to poor contacts and interference at patchbays.
     

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