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  • Class D amplifier question.

    I know I have been talking about busking etc. etc. but I one more question.

    A friend loaned me a 350w inverter and tried to convince me that was ll I needed. When I hooked it up to one of PRX 612's it kicked the breaker in the inverter. There was nothing plugged into the JBL.

    Question -

    Do class D's consume power with nothing being demanded of them just sitting at idle? This inverter was 350w ~3 amps. I would think that this amount would at least fire it up. Could it be that it wasn't a pure sine unit? I'm baffled. BTW, I was not going to use this inverter but just thought I'd try it. JBL gave me a future of 510w ~4.25 amps. Could it be that this was with it doing nothing?

  • #2
    The inverter had inadequate current capabilities to sustain startup of the SMPS. Made even worse with non PSW inverters, but I think the inverter is not large enough. You really do want a PSW inverter though.
    -------------------------------------------------------------------------------------------------------------------------------------------------------------------
    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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    • #3
      Thanks AH for the reply. Like I said, this guy loaned it to me telling me that it would do the trick (I knew it wouldn't) but I was surprised that it wouldn't even do it with the 612 in a no load situation. I have an 1800w PSW on the way which should easily power both 612's.

      BTW, what is a SMPS?

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      • #4
        You want the pure sine wave inverter when you are dealing with computer chips and such and they cost more quite a bit more than the . I seriously doubt you need a 1600 watt inverter. I would bet a 750 watt PSW would run your speaker no problem.
        Dan Snyder is bad Karma

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        • #5
          I know I could have gotten by with less but I have always been the type of person that buys more than I need. Plus, I got a good buy on this one.

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          • #6
            A better quality supply producing a true sine wave will certainly run 99% of your digital fx equipment, amps, synths and laptops etc. with no hassle at all, just as you would expect if you were plugging in at home.
            The best advise if you are unsure as whether to take the risk and go for a cheaper MSI would be to test it out before you buy. Any respectable dealer will allow you to test the inverter on your set up and give you the opportunity to return it, if it’s not right for your system

            MSI is the modified Sine Wave=cheaper unit squares off the wave

            I think the important thing is get a Pure Sine Wave
            Dan Snyder is bad Karma

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            • Telecruiser
              Telecruiser commented
              Editing a comment
              Nope, like I said, I have an 1800w PSI on the way. Got a good deal and it's new.

          • #7
            Originally posted by Telecruiser View Post

            BTW, what is a SMPS?
            Switch Mode Power Supply. That's what makes the new generation of power amps light in weight (not class D). There's a lot of voodoo in the design of SMPS. They are reasonable difficult to initially turn on (which is what Andy was referring to). Basically you set off a small nuclear device to get them started and then they run.
            Don Boomer

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            • agedhorse
              agedhorse commented
              Editing a comment
              Yup, kaaaa-boom!

              PSW inverters are just as important (or more-so) with analog gear where the noise floor depends on a low THD power source. Stable voltage that follows the sine wave laws is also helpful.

          • #8
            With 1800 watts you will have no problem using your power saws and powering up most things in your home in case you lose power.
            Dan Snyder is bad Karma

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            • #9
              I made the mistake of connecting a pair of Class D Peavy IPR's to a MSW inverter. They went down immediately. Actually had a lot of problems with those amps so they went away.

              A&H GL2800 console, BagEnd Crystals over D-18's, 12"and 15" BagEnd and EAW wedges powered and processed by QSC, Klark, BSS, Symetrix, Valley, Sabine, Peavey and BagEnd INFRA.

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              • #10
                Thanks guys, you helped me a lot! This whole process I'm going through for a one time project has taught me a lot.

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                • #11
                  Originally posted by dboomer View Post

                  Switch Mode Power Supply. That's what makes the new generation of power amps light in weight (not class D).
                  So SMPS is not class D?

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                  • #12
                    Correct. SMPS is a type of power supply. It could be used with any class of amplifier.
                    Don Boomer

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