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Thread: Total Noob

  1. #1

    Total Noob

    While I have used some audio equipment in the past, I have been tasked with setting up a sound system for a 32,000sqft trade-show event. I have the following equipment available: Behringer 1222FX mixer with 16 inputs, rackmount CD player for background music, 2 wireless mic systems with headsets for demonstration presenters, 2 stand mics, 1 for the announcer and 1 for a vocalist plus extra mics if needed.

    All of this I am pretty familiar with as far as getting it hooked together. My issue is with the downstream system, the amps and speakers. The venue provides these systems (really decent, have had no feedback issues with any of the mics and sound quality is excellent) except I have a single connection (XLR) to them. Soooo, how do I connect a mixer with stereo outputs to a mono amplifier setup and send all signals to that single output? I know not to 'y' connect the output of the mixer.

    I know I can pan the mic inputs to one side (say all panned to the left, or actually leave them centered) and use that side (L) for the output. What about the CD/tape inputs that have no pan control? Is it better to y-cable the output of the CD player to a single line and plug into the L port of the CD in?, or adapt the output from RCA to 1/4" and use one of the 5/6 1/4" inputs on the mixer that has pan control?

    Also, will I run into issues with mixer life if I use only one output consistently? Is there anything I should do with the other output (terminate to a signal sink to balance the mixer...?)
    Thanks for any help

  2. #2

    More:

    Also, I have to get all the cabling for this. Is there any special cable I need for routing mixer output to the amp? The run is between 25 and 50' from announcer stage to amp input port. Thanks

  3. #3
    If you have a stereo source, plug it into 2 mono channels in the mixer and pan both to one side. You probably can't do this with a stereo line-in channel, 'cuz it will keep left and right separate. (Unless the channel has a "mono" switch - can't imagine why more boards don't.)

    No life-expectancy problems using just one output. You do know, I assume, that if you're feeding an unbalanced amp input you need to take the mixer output from pin 2 and let pin 3 float.

    But you're probably not, since the input you're driving is an XLR. Take balanced board output from one channel to the XLR in, no special cables required. Just regular shielded mic cable.

    You may run into an issue if the system's XLR input is a mic-level one; the mixer will overload it. Better bring an in-line pad along just in case.

  4. #4
    Not sure about the 1222FX but some mixers will have a mono out or a mono aux-out that you can set to be post-fader and set all of the inputs to that aux channel to unity.
    Eric Adler (tonsofpcs)
    http://www.videoproductionsupport.com/ Chat at: http://tinyurl.com/vpschat
    Follow me on twitter: @videosupport @eric_adler

  5. #5
    Hmm. Just looked up the mixer, and the specs aren't too clear what's mono. But it's a small mixer; my previous suggestion of using two mono channels for the CD isn't a good one, cuz that leaves you with almost no mic inputs.

    Can you solder? The proper way to mono a CD player is to make up a Y-cord with a resistor in series with each of the two channels. Anything from 2K to 5K will work. One end of each resistor goes to one channel of the CD player, the other ends are joined together and go into the mixer. All the shields are connected together.

    Not every CD player needs this. More modern ones are often designed with Y-cord use in mind. But there's no way to be sure, ahead of time, unless you can look at the CD player's user manual. There's an outside chance you could damage the CD player, which could lead to political problems especially if the player isn't yours.

    If you frequently do sound work, it's a good idea to have some resistor-enabled Y-cords of various types, and an isolation transformer, and carry them with you.

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