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I often do live sound reinforcement for events at our church services. We have lately been using Behringer 212D speakers. During an event today I found that if I turned the main output volume down suddenly a loud hiss and hum were introduced, and if I turned it down further the speakers turned off completely!

Both of these problems completely went away when I turned the volume back up over a certain threshold.

Looking into this I found that the 212D speakers have an "undervolt circuit protection" feature that will turn off the amplifier when the input voltage is too low. This seems to be what we were running into. However, I am running a line out from an EQ (after the mixer) and it seems strange that I would run into this. I do split this line using a fully stereo (balanced) phono cable (all three connectors are balanced and all cables and all equipment are balanced).

So, is it maybe that the splitter is cutting the voltage in half? Or maybe somehow the speakers being connected to the same line is confusing the circuitry? Or am I way off base here?

Thank you for your help.

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For migration to SD please Tim –  Rory Alsop Jan 27 at 16:13
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2 Answers

You can also feed the two destinations from separate outputs of your mixer, if it happens to have these. Sometimes a mixer will have AUXilliary or MONitor outputs as well as the main, and often times it is easy to feed these with the same signal as the main outs... though not always.

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Yes. This is what we are going to do. The mixer has a left and right output and we have a multi-channel eq. When I need 4 speakers I will just have to do a different setup. I wish I could better understand what is happening but for now this will work. –  Practicality Mar 28 '13 at 13:20
    
I tend to advise against using an aux or monitor send for your mains (at least if you are also sending from the main output to other parts of the Mains) as it is too easy to accidentally send different feeds with hard to troubleshoot results. A DA is a much safer approach if consistent signal duplication is necessary. –  AJ Henderson Mar 28 '13 at 13:26
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A passive splitter will reduce the signal strength. You could use a Distribution Amplifier to keep the signal level consistent while going to multiple outputs. I'm not sure if that is the source of your problem or not, but it might be worth a shot. I would suggest trying it without the passive split first and see if that fixes the problem or not. If so, I'd try a DA.

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This is a good suggestion. I will give it a try with a test setup some time and see if I can duplicate the problem, and then fix it with this. –  Practicality Mar 28 '13 at 13:22
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