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Can I run a mixer/preamp with no load on one channel?

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  • Can I run a mixer/preamp with no load on one channel?

    I am getting a few very small gigs, where one powered speaker will more than do the job and space is extremely limited.

    I run a Samson MPL1204 mixer which feeds two EV-ZLXP powered speakers.

    Can I run the mixer with only one speaker (no load on the other) without damaging the preamp?

    I remember in the tube days this was a no-no, but I'm not sure if this has carried over to solid state. (I went to school a looooong time ago).

    Thanks,
    Bob
    Bob "Notes" Norton
    Owner, Norton Music http://www.nortonmusic.com
    Style and Fake disks for Band-in-a-Box
    The Sophisticats http://www.s-cats.com >^. .^< >^. .^<

  • #2
    Really nothing to do with tubes, per se, Notes, but everything to do with output load balancing on 'stereo/2 channel' power amplifiers. Your set up does not have any 'stereo' power amps...it is a passive mixer going into powered speaker[s], so as long as everything is panned to one side on the board, it should be okay. When the load was being generated in the mixer's internal amp, or feeding a separate power amp, then you needed to balance the outs. I've run 'small gig' PAs this way for years.
    Last edited by daddymack; 05-15-2019, 02:03 PM.
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    • #3
      Thanks!

      We got a call from an agency to do a model home grand opening tomorrow, but we were asked to conserve space as much as possible. It pays well for 2 hours of work, so we'll just pan to one side.

      We run mono anyway. Would turning the output fader to infinity on the unused channel do the same thing?

      Notes
      Bob "Notes" Norton
      Owner, Norton Music http://www.nortonmusic.com
      Style and Fake disks for Band-in-a-Box
      The Sophisticats http://www.s-cats.com >^. .^< >^. .^<

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      • #4
        Unless it has a power amp built into it, you can run a mixer with nothing connected to the outputs if you want. The only time you have an issue is when you're running a power amplifier with no load... that's a BIG problem. But in your setup, the power amp is built into the speaker cabinet and not the mixing board, and the onboard speakers provide the proper load for the powered speaker's built-in amp.

        You have nothing to worry about if you want to connect only the left or right output of a non-powered (i.e. no onboard power amp) mixer into a powered speaker.
        **********

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        • #5
          yes, but you should have pulled it down all the way anyway...infinity...and beyond!
          "We are currently experiencing some technical difficulties due to reality fluctuations. The elves are working tirelessly to patch the correct version of reality. Activities here have been temporarily disabled since the fundamentals of mathematics, physics and reason may be incomprehensible during this indeterminate period of instability. Normal service will be restored once we are certain as to what 'normal' is."

          Life's journey is not to arrive at the grave safely in a well preserved body, but rather to skid in sideways, totally used up and worn out, shouting '...man, what a ride!'

          "The greatness of a man is not in how much wealth he acquires, but in his integrity and his ability to affect those around him positively" ~Bob Marley

          Solipsism is the new empiricism. -Alan Burdick

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          • #6
            Yes you can leave the output unconnected, power amp or no. You do not need to pan to one side either.
            Don Boomer

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            • #7
              Thanks y'all.

              One less speaker to schlep, and more than that, a compact footprint for the client.

              They are for furnished model homes. Sales parties where realtors are invited and given incentives to show their clients these houses. We did a couple for this realtor, and they want us as their first choice for a number of others.

              Easy gigs, 2 hours, no pressure, play just about anything, just keep it happy. And they pay well.

              Just livin' the dream

              Notes
              Bob "Notes" Norton
              Owner, Norton Music http://www.nortonmusic.com
              Style and Fake disks for Band-in-a-Box
              The Sophisticats http://www.s-cats.com >^. .^< >^. .^<

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              • #8
                Originally posted by Notes_Norton View Post
                I am getting a few very small gigs, where one powered speaker will more than do the job and space is extremely limited.

                I run a Samson MPL1204 mixer which feeds two EV-ZLXP powered speakers.

                Can I run the mixer with only one speaker (no load on the other) without damaging the preamp?
                Absolutely. As long as you're not running power through an inductor (as with a tube amplifier with an output transformer) there's no problem with an unloaded line level output. Just pan all the inputs to one bus and connect that bus output to your amplifier or powered speaker.
                --
                "Today's production equipment is IT-based and cannot be operated without a passing knowledge of computing, although it seems that it can be operated without a passing knowledge of audio." - John Watkinson, Resolution Magazine, October 2006
                Drop by http://mikeriversaudio.wordpress.com now and then

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                • #9
                  Originally posted by dboomer View Post
                  Yes you can leave the output unconnected, power amp or no. You do not need to pan to one side either.
                  Well, a pan pot usually has a 3-4 dB dip in the center to compensate for the boost in levels when both channels are summed equally to each of the two pan pot outputs. It's no big deal, but by setting all the pan pots fully to one end and not the other, you don't have a little ambiguity in the center, even if the pots are detented.

                  I replied before I read your reply. Hard-panning to the output that I'm using when I'm only using one is something that I just do on good faith.
                  --
                  "Today's production equipment is IT-based and cannot be operated without a passing knowledge of computing, although it seems that it can be operated without a passing knowledge of audio." - John Watkinson, Resolution Magazine, October 2006
                  Drop by http://mikeriversaudio.wordpress.com now and then

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                  • #10
                    Originally posted by MikeRivers View Post

                    Well, a pan pot usually has a 3-4 dB dip in the center to compensate for the boost in levels when both channels are summed equally to each of the two pan pot outputs. It's no big deal, but by setting all the pan pots fully to one end and not the other, you don't have a little ambiguity in the center, even if the pots are detented.

                    I replied before I read your reply. Hard-panning to the output that I'm using when I'm only using one is something that I just do on good faith.
                    I know you know this Mike, but for those that don’t ... That 3dB might help or hurt just depending. Most powered speakers don’t need much drive and most users don’t have correct gain structure anyway. Do in that case lowering the drive is a help.
                    Don Boomer

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                    • #11
                      Thanks again y'all.

                      Notes
                      Bob "Notes" Norton
                      Owner, Norton Music http://www.nortonmusic.com
                      Style and Fake disks for Band-in-a-Box
                      The Sophisticats http://www.s-cats.com >^. .^< >^. .^<

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