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Digital mixer use with a non-inverter generator

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  • Digital mixer use with a non-inverter generator

    Over the course of the year I provide the sound system for a couple of annual outdoor events that use non-inverter generators for stage power. My contract states that my rig requires "hard-wired" power thus when, three years ago, a particular generator decided to stop producing power (mid show) I let the show's producer figure out a solution. (He ended up going to a local harborfreight and bought a Predator4000 generator.) Everything got up'n running and the show continued.

    My question: On non-inverter powered gigs I always bring my Mizwizard as I am skeptical about using my digi QU mixer....
    If I were to purchase a unit such as: Tripp Lite Avr Avr550u - Ups - Ac 120 V - 300 Watt - 550 Va - 8 Output Connector(S) to use with the QU mixer would that unit provide stable-enough power on non-inverter power (plus backup power for me to safely power-down the mixer in the event of a generator failure)?

    I'm getting used to my Allen & Heath QU mixer and would prefer to use it all of the time if possible.
    Last edited by Mike M; 07-31-2016, 07:00 AM.

  • #2
    The fact that the producer went to Harbor Fright to get anything would be sending off signals to me. I would be so easy for him to just rent a proper generator and be done with it.

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    • #3
      It's so easy for the promoter to rent a Honda 4KW inverter generator instead of using that HF POS that you really should twist his arm a bit...

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      • #4
        Originally posted by Mike M View Post
        Over the course of the year I provide the sound system for a couple of annual outdoor events that use non-inverter generators for stage power. My contract states that my rig requires "hard-wired" power thus when, three years ago, a particular generator decided to stop producing power (mid show) I let the show's producer figure out a solution. (He ended up going to a local harborfreight and bought a Predator4000 generator.) Everything got up'n running and the show continued.

        My question: On non-inverter powered gigs I always bring my Mizwizard as I am skeptical about using my digi QU mixer....
        If I were to purchase a unit such as: Tripp Lite Avr Avr550u - Ups - Ac 120 V - 300 Watt - 550 Va - 8 Output Connector(S) to use with the QU mixer would that unit provide stable-enough power on non-inverter power (plus backup power for me to safely power-down the mixer in the event of a generator failure)?

        I'm getting used to my Allen & Heath QU mixer and would prefer to use it all of the time if possible.
        The unit you linked is a line-interactive unit. While it should be okay handling over and under voltage conditions, I'm not certain it will do much with frequency instability. You should contact the manufacturer and ask (or maybe there's a useful spec available).
        "If you don't know where you are going, you might wind up someplace else" - Yogi Berra, 1925-2015

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        • #5
          When you sleep with snakes in your pocket, at some point you are bound to get bit. I don't think it will matter all that much which mixer you are using ultimately.
          -------------------------------------------------------------------------------------------------------------------------------------------------------------------
          Former product development engineer: Genz Benz, a KMC Music/FMIC/JAM Industries Company, continuing factory level product support and service for Genz Benz

          Currently product development engineer: Mesa Boogie

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          • #6
            $94? I don't need to read the spec to know that it will not correct frequency problems.

            In fact, I was surprised to find that it can even correct voltage, but the spec sheet says it can. This is likely one of those guys with a multi-tap auto-transformer and relays to pick the right tap based on the input voltage, to keep you close to your 120V target.

            https://www.tripplite.com/avr-series...-port~AVR550U/

            Good news, non-inverting generators tend to have nice waveforms, and most of this equipment is not overly sensitive to minor frequency variations (especially gear with world-compatible power supplies). But What Andy Said.

            Wes
            Last edited by wesg; 08-02-2016, 12:38 PM.
            Do daemons dream of electric sleep()?

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            • #7
              When the cheapie generators start to run out of gas (or malfunction) they start to hunt and slow down - the resultant brownout and low frequencies aren't equipment friendly . The inverter generators should just drop out without sending nasty power to your gear .

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              • #8
                Say, that's a good advantage!

                The reason I mentioned "world-compatible" power supplies was that they are, by definition, good down to 50Hz. This means beefy iron if they are linear supplies! Hopefully a non-inverting generator would never dip below 3000rpm (for a 3600rpm governor) but you're right, it could totally happen under those circumstances.

                Wes
                Do daemons dream of electric sleep()?

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                • #9
                  The problem is the cheap gennies struggle with correcting the field current (which is what regulates the voltage) under dynamic loads, especially with the loss of mechanical frequency integrity.
                  -------------------------------------------------------------------------------------------------------------------------------------------------------------------
                  Former product development engineer: Genz Benz, a KMC Music/FMIC/JAM Industries Company, continuing factory level product support and service for Genz Benz

                  Currently product development engineer: Mesa Boogie

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                  • #10
                    Thanks, Andy. That's very useful information. Every time I learn something new about how inexpensive generators operate "in the field", the less like I am to use one on a gig.

                    I'm wondering now if I should even plug my (modern) fridge into the unit I use for power outages in my home. Maybe I should just keep the water pump and USB charger on it.
                    Do daemons dream of electric sleep()?

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                    • #11
                      Generators are in concept very simple, the control systems straight forward. In practice, the prime mover (engine) is not ideal, leading to frequency and voltage variations, plus the feedback from the output voltage to field current conversion is less than precise because the changing load simultaneously affects voltage and current. At the voltage falls, the field current increases which increases the load on the prime mover, which causes the voltage to fall some more (in addition to frequency). The control loop can't be too fast (too much gain) or the voltage will hunt (oscillate). The engine speed is controlled by a governor, which has its own control loop to try to maintain frequency. These two control loops can interact as well.

                      This is why commercial generators are usually more heavily built, with more ideal curves and properties. The bigger the generator, the more sophisticated the entire control package (including the mechanical "idealness" of the basic process)
                      -------------------------------------------------------------------------------------------------------------------------------------------------------------------
                      Former product development engineer: Genz Benz, a KMC Music/FMIC/JAM Industries Company, continuing factory level product support and service for Genz Benz

                      Currently product development engineer: Mesa Boogie

                      Comment


                      • #12
                        Indeed, the larger the generator package, the more forgiving the weight requirements can be, so it's possible to have an engine with sufficient rotating mass to sustain RPM's through minor running problems...which are far less frequent with a larger and higher quality engine. Adding the mass of a flywheel is a big weight penalty, but goes a long way to maintaining consistent speed easily.
                        "If you don't know where you are going, you might wind up someplace else" - Yogi Berra, 1925-2015

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                        • #13
                          Just wondering would a 50 amp. Generac Generator which I have in my Motorhome work ? It has a 20 amp and a 30 amp circuit breaker on the Generator.

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                          • #14
                            Also would it put anyone on the spot to recommend a particular Generator? Thanks

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                            • #15
                              Originally posted by Stingray5 View Post
                              Also would it put anyone on the spot to recommend a particular Generator? Thanks
                              Any of the Honda inverter generators, they have 1000, 2000, 3000,and 7000 watt versions I think. Yamaha has some inverter generators too.

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