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"no laptops used may be plugged into ac power" how to get round this

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  • "no laptops used may be plugged into ac power" how to get round this

    a gig i'm working with in mid january is being run by someone who, from past experience, is very stubborn, and also very smart. he tends to do things that make little sense, except to him. heres the latest one, and i'd love some input for this.



    we have dances each night of the event which require djs. most of the djs are using laptops with external controllers, external hard drives, etc. the guy in charge of the soundsystem has insisted that no laptops can be plugged into ac power because they create to much crosstalk and noise in the soundsystem.



    i have experienced this, but it was solved effectively with a di with ground lift switch and some 1/4 to 1/8 cables. it has never been a problem after this is done.



    if i can not convince him that di boxes and 1 to 1 transformer isolation can solve this problem, i will lose half or more of the djs. i want to present reasoned arguments and handle this diplomaticly, because thats the only way i'm going to get things done with this guy, and besides its more professional.



    please help!

  • #2
    Have you considered a different soundguy that is capable of working the gig?
    <div class="signaturecontainer">Good judgment comes from experience, and a lot of that comes from bad judgment. -Will Rogers<br><br><a href="http://facebook.com/SpitShineRocks" target="_blank">http://facebook.com/SpitShineRocks</a></div>

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    • #3
      I guess the first thing would be to ask him if he'll even listen to the proper way to do it. If he's so stubborn that he won't then getting a bunch of info is a futile effort. I've used an 1/8 to 1/4 mono into a do and out to foh for years and never had one problem. You know the same. Are you hoping that he'll believe you or are you trying to find another way to convince him?

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      • #4
        The first plan of attack would to use ground lifted, transformer isolated DI's (not active). Under some conditions a special transformer with dual electrostatic shields can be necessary due to RF capacitively coupled across the transformer.



        Now this works 95% of the time, but there are some switching power supplies that are very noisy, and on some laptops they can cause HF ripple currents to flow where they should not flow and cause noise that can not be resolved with a DI (because the because the cause is unrelated). This is where eliminating the power supply can really help. Just had this happen with an apple notebook, fully transformer isolated but HF noise was being coupled across the transformer. He plugged the power supply in at intermission and I saw signal on the meter but could not hear it. It was oscillation >20kHz, something that you want to avoid because of the potential for damage. Unplug the supply, the interference was gone.

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        • #5






          Quote Originally Posted by Mutha Goose
          View Post

          Have you considered a different soundguy that is capable of working the gig?




          Maybe one that doesn't suck?

          "We Have Met the Enemy and He is Us" - Walt Kelly​

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          • #6






            Quote Originally Posted by agedhorse
            View Post

            It was oscillation >20kHz, something that you want to avoid because of the potential for damage. Unplug the supply, the interference was gone.




            No LPF's on the channel strips? Guess I'm spoiled with running digital .

            "We Have Met the Enemy and He is Us" - Walt Kelly​

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            • #7






              Quote Originally Posted by RoadRanger
              View Post

              No LPF's on the channel strips? Guess I'm spoiled with running digital .




              Sometimes the problem is ground current related... ie. injecting RFI into the grounds via the LPF's if the signal is strong enough.



              If it's getting in over the audio inputs, generally, the LPF's are set (by design) with the -3dB point around 30kHz, so if the noise is even 40-50kHz and strong enough, it can certtainly be a problem.



              It depends on how the noise is getting in, and what it is. I didn't have the equipment on hand to analyze this, and certainly not DURING the show

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              • #8
                the guy in charge is grandfathered in for years and years..one of those "he'll do it for free" type things and i'm regretting my involvement with this whole thing at this point, but it'd be rude to back out now. anyone else ever worked a fan based convension like for anime or treckies? i shouldnt have.

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                • #9
                  Nope, I don't have the patience to do so, certainly not for free.

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                  • #10
                    So I'm assuming that you can't get enough power with the built-in battery? Does your laptop have an extended range battery available? How about swapping to a new battery mid show?
                    Don Boomer

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                    • #11






                      Quote Originally Posted by spottyaudio
                      View Post



                      we have dances each night of the event which require djs. most of the djs are using laptops with external controllers, external hard drives, etc. the guy in charge of the soundsystem has insisted that no laptops can be plugged into ac power because they create to much crosstalk and noise in the soundsystem.





                      if i can not convince him that di boxes and 1 to 1 transformer isolation can solve this problem, i will lose half or more of the djs. i want to present reasoned arguments and handle this diplomaticly, because thats the only way i'm going to get things done with this guy, and besides its more professional.



                      please help!




                      I'm not sure what you're function is at this gig, but why not ask him to allow the DJ's to use an isolating device (supplied by him) UNLESS he is still experiencing noise. Then he gets to literally pull the plug. The DJ's would have to be warned in advance, but most would probably still be willing to do the gig, because humans usually reckon that things will work the way they want them to.

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                      • #12
                        Bring a bunch of stereo direct boxes and small sub mixer
                        <div class="signaturecontainer"><a href="http://www.rock-bot.com" target="_blank">www.rock-bot.com</a><br />
                        Live-Band-Karaoke<br />
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                        bassist and sound reinforcement</div>

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                        • #13
                          all valid points, i thank you. i have a good few stereo diboxes i plan to make available, some of which are customized with rca and 1/8 inputs specificly for this purpose. i just have to get past someones obstinence to use them.

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                          • #14
                            What is your role in all of this?

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                            • #15






                              Quote Originally Posted by spottyaudio
                              View Post

                              the guy in charge is grandfathered in for years and years..one of those "he'll do it for free" type things and i'm regretting my involvement with this whole thing at this point, but it'd be rude to back out now. anyone else ever worked a fan based convension like for anime or treckies? i shouldnt have.




                              Yup, you screwed yourself there for sure. Always remember "No good deed goes unpunished" . Personally I'd just pull out saying you can't work with the sound provided - no reason to ruin your rep dealing with those idiots .

                              "We Have Met the Enemy and He is Us" - Walt Kelly​

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