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Side Chain

Discussion in 'Sound, Music, and Intercom' started by Schniapereli, Feb 28, 2007.

  1. Schniapereli

    Schniapereli Active Member

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    At our school, we have a Behringer AutoCom Pro MDX1400. I have read the manual, and it says that the compressor can do "ducking" so you can hook up a mic and music to it using the mic as the sidechain, and then the music will back down whenever someone uses the mic.

    What I have done so far is have a mic sending a signal through Aux 1 to SC return, (using a TRS cable) and have music go through Aux 2 to the Compressor input (with a TS cable). Then, the output was an XLR cable to a channel on the mixer. (no more balanced TRS's) I have tried all the buttons and knobs in different places.

    I have played with this a lot and I have not yet gotten it to work. How do you set it up? (what from mixer to where, etc.) And what settings to you make on the compressor. I have tried just about everything I can think of. What am I doing wrong?
     
  2. DarthFader

    DarthFader Member

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    Hello,
    I haven't used the Behinger box, but what you would typically do is send the the mike audio to SC input, (not return) via the aux, and insert the compressor in the music channel. Sending the music on an aux and returning to a channel should also should work, but uses more of your resources. Turn the compression ratio as high as it goes Turn the threshold all the way down. Send enough signal on the mike aux to light the gain reduction lights. If they are not lighting you won't get any ducking effect. I see that the Beringer has a button for external SC so you will want that enabled. You should now have way too much ducking effect, so start backing off your compression ratio and increasing the threshold till you get it to sound the way you want. As a starting point try for six to 12 db of compression when you talk into the mike. You will want a quick attack, and very slow release to fade the music back up when the speaking stops. Lots of fun things to do with side chain if you have the time to play with it. Hope this helps
     
  3. Schniapereli

    Schniapereli Active Member

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    Our compressor only has SC send, and SC return. Is input different from return? I would think they mean the same thing...but you said "not return"... but then again, I had it set up the same way (return instead of input) but it didn't work.

    Is it possible that it is just broken? I have never been able to hear the SC input except when I was monitoring it. (or, maybe there is something else I am doing wrong)

    Also, we have no insert cables, so that is why I have to use all of thse cables. We are looking into buying some (it's through the school, so it will take a while) but for right now, all we have is 1 TRS cable (4 inches) and a whole bunch of TS cables (lenghts from 2 feet to 25 feet)
     
  4. Andy_Leviss

    Andy_Leviss Active Member Premium Member

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    Send=Input (it sends signal from the console to the processor)
    Return=Output (it returns the signal to the console)

    In your situation, you don't need the return at all; it's used in cases where you're trying to link multiple compressors together, you'd use the send from signal B's insert point to A's sidechain, and then the sidechain return would go to B's input, and B's output would go to that the return on the console. That way the signal on B would trigger both channels in unison.

    --A
     
  5. Schniapereli

    Schniapereli Active Member

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    ...ah... that's what I kinda thought it would be... I didn't have enough sense to actually try that though...

    Well cool. I still haven't gotten used to all of the knobs, so I'll tinker with that. Darthfader's explanation will help a lot though...

    And, is this universal? I mean does "send" mean input and "return" mean output on other compressors, etc. or maybe just on certain brands? I don't have that much equipment, but that is the only place where I have seen that.
     
  6. DarthFader

    DarthFader Member

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    Your reply sent me off to the Behringer web site to investigate the downloadable manual. What a model of how not to write a manual! In the specs it refers to side chain input and output. In the text and aparently on the unit the labels are send and return. I don't see how send and return apply to a compressor actually, but I stand half corrected. Where you want to send the signal is to the sidechain input (as I said before), but Behringer has decided to label the jack return.
    Sooooo.... try this.


    1. Send your music on either TRS or XLR to the appropriate jack in Channel 1's "Input" section. From Channel 1's "Output" run a TRS or XLR back to your board.


    2. Don't assign the music you are sending to your mix (speakers). Only assign the channel that is driven by the signal coming back from the compressor.


    3. Don't activate the SC External Switch yet. We want to get the thing compressing in normal mode first. Turn up the signal level you are sending till you see some gain reduction lights coming on. Turn up the ratio and turn down the threshold contols till you see lotsa lights flashing.


    4. Now bring up the gain on the channel coming back from the compressor. With all the compression we have cranked in it should sound awful. If not, change the "IN/OUT" switch to the opposite position. In one position or the other you should hear a volume compressed version of the original. If you aren't heqaring that, try the other position of the "SC EXT" switch. I won't assume what function Behringer gave to the depressed or released position. In some combination you should be able to hear the compressor in action. Setting it to compress heavily makes that easier to hear.


    5. Once you have that happening, set the "SC EXT" to the opposite position and send the mike signal to the side chain return jack with a TS cable. These are unbalanced inputs and TS is all that is needed. You don't need to assign the mike to the mix yet. Now you should be able to talk into the mike and see the gain reduction lights flash. Adjust the ratio, threshold, attack and release times as well as the mike signal if needed.
    6. Assign the mike to your mix. You now have two channels in the mix. The output of the compressor, and the mike. Don't assign the channel that is being used to send the music to the compressor.


    7. If you do all this and it still won't function, walk to the tool drawer, select a large ball peen or small sledge hammer....stand by for more instructions.


    Good Luck
     
  7. Andy_Leviss

    Andy_Leviss Active Member Premium Member

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    Yes, although you'll only see it labeled as such on a console, in which case it's reversed, and on dynamics processors with sidechain inserts.

    The rule is that the signal sends from the console, and returns to it.
     

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