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Horrible noise through monitors when laptop is plugged in...

Discussion in 'Monitoring / Headphones' started by qwerty11, Jan 4, 2009.

  1. qwerty11

    qwerty11 Guest

    I have tried all different types of connections and I get horrible noise when the laptop is plugged in. I have tried plugging up stuff all over the studio, putting them on power grids, and what not. Is there anyway to get around this problem. I figure the converter is creating some crazy feedback.
  2. Greener

    Greener Guest

    Ground loop problem.
    You need a better power supply for the laptop and something like what was suggested to me by GentleG, I haven't tested it but here is the link.
  3. Link555

    Link555 Well-Known Member

    When you say plugged in, do you mean to power?
  4. qwerty11

    qwerty11 Guest

  5. Link555

    Link555 Well-Known Member

  6. qwerty11

    qwerty11 Guest

    $80 seems a lot for that little dude. Is their cheaper alternatives or can you make your own?
  7. Link555

    Link555 Well-Known Member

    Its a transformer, yes you can make you own. But after having made a few myself, $80 is a Bargain ;)
  8. pr0gr4m

    pr0gr4m Well-Known Member

    The cheap and dangerous solution is to use a ground lift. It's a little plug adapter that converts a 3 pronger into a 2 pronger.

    It's cheap cuz those things are like 98 cents. It's potentially dangerous because you are removing the ground which could cause your equipment to fry if there was a power surge.

    I've used them before without any problems.
  9. Link555

    Link555 Well-Known Member

    Sorry Program, I would never consider that as a option. Its a fire hazard at the very least, it could lead to death. The grounds are there for a reason, they shunt any dangerous spike to earth with a lower impedance path than your body does.

  10. Greener

    Greener Guest

    I agree.

  11. Codemonkey

    Codemonkey Well-Known Member


    God doesn't like it.
  12. qwerty11

    qwerty11 Guest

    How about taking a wire from the ground wire of the power grid and running it to a grounding rod stuck into the ground outside?
  13. Codemonkey

    Codemonkey Well-Known Member

    I think that's essentially what already happens...
  14. Boswell

    Boswell Moderator Distinguished Member

    This has very little to do with the quality of the ground and much to do with the quality of the laptop power supply. Isolating a noisy supply using a transformer doesn't make it any less noisy. Get a better mains power supply, or run the laptop off a 12V car adaptor fed from a 12V d.c. linear mains supply.
  15. GeckoMusic

    GeckoMusic Guest

    Don't remove the ground pin on your AC outlet.

    I've been able to eliminate the power supply noise by using a DI with the ground lifted.

    Also try plugging the laptop and the mixer into the same outlet. In residential electrical wiring half of the outlets are out of phase with the other half. This makes the power company happy, but audio engineer ... bald.

    Using a USB sound card that has a transformer isolated output can also work.
  16. qwerty11

    qwerty11 Guest

    What is a DI?

    I have been thinking about getting a cheap desktop (i.e. - http://cgi.ebay.com/Dell-Optiplex-GX280-P4-2-8-1024-40-Combo-Speakers-LP_W0QQitemZ120361369623QQcmdZViewItemQQptZDesktop_PCs?hash=item120361369623&_trksid=p3286.c0.m14&_trkparms=66%3A4|65%3A15|39%3A1|240%3A1318)

    Would the humming likely stop with a desktop?

    Would this computer be good enough to run everything?

    My laptop is top of the line however.

    Where can you buy mains power supplies?

    I didn't understand what you was saying about the power inverter thing. Could you elaborate more?

    I have a deep cycle 12v battery that I could hook an inverter up to to run the laptop. Would that work?
  17. GeckoMusic

    GeckoMusic Guest

    1. DI = Direct Inject. This is probably your cheapest option if the free ones didn't work. Search your favorite online gear dealer for "DI" or "DI box" or "Direct Box"

    2. Desktops do not have this problem
    3. The computer you have selected should be fine for home recording, but it depends on the load that your plug-ins have. Simulated synthesizers and cabinet cims and other resource hogs will kill it for you.

    Or just use a power conditioner or UPS (uninterrupted power supply) if that is really the problem. Make sure to get one powerful enough for ALL your audio gear.
  18. qwerty11

    qwerty11 Guest

    So this is what you are talking about?

    How would I hook it up to my system?
  19. GeckoMusic

    GeckoMusic Guest

    Yes, that is a DI. The variable pad is overkill for the application. Any passive DI will be easy to use. If you get a 2 channel DI (or two DIs) you can run stereo. Or get one with a linked input and connect the left and right to the two linked inputs. Or get two cheep passive DIs.

    Computer -> DI -> Mixer
  20. dvdhawk

    dvdhawk Well-Known Member

    This is what I use on my installs if connecting the 1/8" stereo mini from a computer to a sound system.


    I agree with Link555 you would hard pressed to build one for much less. What you would save would hardly be worth the bother, burns, and band-aids.

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