Your Questions: Fixing Laptop Hum When On AC Power?

If you're plugging in to a mess of other cables and gear, try and make a clean break and distance yourself from potential causes of AC hum. Pic from: milestek

If you're plugging in to a mess of other cables and gear, try and make a clean break and distance yourself from potential causes of AC hum. Pic from: milestek

Regular reader and DJ Big Clive asks: "Having trouble with laptop noise through my speakers when my power supply is plugged into my laptop. Thing is, if it's on battery there is no noise. Can you help?"

Digital DJ Tips Says:

This is thankfully not as common a complaint with today's gear as it used to be, but nonetheless it is annoying, because it's sometimes hard, if not impossible to diagnose what exactly is causing it. Even if you can, it can be tricky to rectify.

Three things to try

Here are two things that helped for us when we had a similar problem two laptops ago, and a suggestion that we didn't try but that may solve the issue. These ideas come in cost order, cheapest first!

  1. Try putting the power supply as far away from the laptop as you can - It's probably the transformer that's causing this, so if you keep the distance between that and the laptop big, it may reduce or even cure the problem. That includes keeping it away from other messy AC cables
  2. Try an alternative power supply - In my experience, power supplies can vary a lot, and a different one may not give you this problem. Worth trying out the replacement first though - you don't want it to make things worse
  3. Try an external audio interface - I am assuming you're using your laptop's internal sound card for your music at the moment. Instead, you could invest in an external audio interface. This is a good investment anyway for sound quality purposes, and I'd be surprised if you had the same problem when using a sound device that isn't actually part of your computer

Hope one of the first two helps you, and if not, why not borrow an external audio interface from a DJ friend and see if that cures it? At least that way you'll know before shelling out the green stuff.

Have you suffered from buzz or hum when connected to AC, but not on battery power? How did you solve it? Please share your thoughts with us and try and help Clive by sharing in the comments.

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  1. Battery chargers from laptops as well as power supplies from pc’s can cause interference in your setup. If you use a desktop pc, try NOT to ground it, even if your wall outlet isn’t grounded at all. The buzz is mostly caused by the laptop charger when using a notebook, so see if unplugging the power cable (running on batteries), helps. Changing a sound card might not help.

    Make yourself a dedicated groundless socket outlet hub! Buy an AC hub and a separate AC plug. Cut off the hub's plug. Open your new separate plug with a screwdriver and connect the wires, but not the yellow ground. Just don’t connect the ground wire to the plug, leave it out or cut it off. Now by connecting your prepped AC plug to the hub the whole hub becomes a hum free outlet. This way you’ll always have several groundless power sockets standby! Use this box for your computers only, then you’ll always be hum free.

    Forget di-boxes and ground isolators! They will destroy your sound without killing the buzz!
    I’ve been using digital vinyl systems since 2003, and this little thing saved my life many times during outdoor setups!

    • Yes! Years ago I encountered the same problem. I found that the new, smaller laptop power supplies had more hum than the larger, heavier, older power supplies, but they both had hum. I learned that grounding the power supply effectivly turnes it into a an antena. The solution is to use use an AC adapter, three prong female to two prong male, eliminating the ground. Always plug your laptop into a power conditioner (not just a surge protector), and pluf that into an outlet apart from all the rest of your equipment. Assure that that outlet is on a different circuit (not the same breaker) as the outlet that the rest of your equipment is pluged into. That will eliminate the hum and protect your laptop. Remember, your laptop is your lifeblood, protect it! Now if I can just get the hum out of my wireless mics!

  2. Every safety warning in the world will tell you not to do this, but I use a 3rd prong isolator on both my laptops to eliminate hum. So, Kids - don't do this - I'm just sayin...

  3. Prof. Deusc says:

    You could also try to remove the battery from the laptop when you plug it (btw it will also lengthen the life of the battery 😉

  4. Called ground splitter xan help

    • andreanegri says:

      Sorry, exists a magic compnent called ground splitter, maybe this can solve the problem, i think the main problem is power plug is the same for laptop and amplifier/speakers.

  5. Ground loops a very common problem for audio and video equipment, that that sounds what you have going on here. While it's great to have the ability to lift the ground (through a 3-2 prong adapter or a modified power strip), it's not an ideal solution for obvious safety reasons. So lifting the power ground should be a testing and emergency solution ONLY.

    There are many ways to address ground loops that won't also possibly involve someone getting electrocuted. First thing to try is to simply plug your computer into another outlet (if one is available). Sometimes that alone will fix your issue.

    If that fails, or there's no outlet available, you're going to need some props. Really, no DJ gig bag should be without one or more of the following...

    GLI (Ground Loop Isolator)
    This is a device you put in the audio signal path that will usually get rid of your hum. For a DVS setup, you will probably need more than one of these (one for each RCA pair between the audio interface and the other powered equipment connected). The upside is that these are cheap and easy to use. The downside is that they negatively effect audio quality a bit. Still, a good thing to have handy.

    Along these lines, you can also use a direct box that has a ground lift. I personally don't like using direct boxes because they're big and usually not RCA. But in a pinch they'll work.

    Next,(and my favorite) is the Ebtech HumX.
    These things ROCK. They live in the power chain, not the audio chain, so they don't impact audio quality. And they work really well, even if you plug the other end into a power strip and use that strip to power all your equipment. VERY worth the money.

    Finally, we can lift the USB ground. Also a good solution that doesn't impact audio quality at all. You can use a USB isolator for this...
    This device has the same kind of galvanic isolation chips used in products like the Serato/Rane SL-1. Plug your isolator into the computer, and your audio interface into the isolator, and you're golden.

    Hope this all helps!

  6. A-Dag-Io says:

    I had the same dilemma, ground hums on my laptop when connected to a PA, running on battery means silence. Then somebody told me that an extra universal power supply might be much better, but you have to be sure it's a groundless one. Most Notebooks have cheap power supplies, most of them grounded, for reasons I don't know.
    Macbooks don't have these problems, as all parts fit perfect together.
    Well that's what I bought, and I never had hums again.

    • Don't be so sure about Macbooks don't having these problems.
      I own a Macbook and a Line 6 UX1 Tone Port External Audio Interface.
      If i unplug the ac cable from my macbook it sounds cristal clear. If i plug it back it starts humming.
      If my hands are on the Macbook, the hum decreases substantially (it remains but almost inaudible).
      Depending on my position with my guitar, for instance, it hums or not.
      I'm considering getting two extra arms so I can play the guitar and touch the Macbook at the same time for grounding. Hehehe
      I've already had two macbooks, always had the same problem.

    • Updating:
      I changed my newest Macbook Ac Adaptor to my oldest Macbook Ac Adaptor and surprinsingly it did the thing. Hasta La Vista damn humm.

  7. Grounded laptop power supplies (3-pin into charger) generally cause ground loop hum. MacBooks and other pcs that only have 2 pins (no ground) usually don't. If you have a 3-pin laptop charger avoid the ground loop and connect the computer to a different wall power outlet than the speakers.

  8. Dj Tom p says:

    Safety first! never work without grounded gear!! Especially when you work next to drunk people+alcohol. The ground connection is a lifesaver from getting electrocuted
    This hum noise is a very common problem and it can be solved easily by adding a ground loop isolator!!! Search YouTube for "ground loop isolator".

  9. Keep one of these in your DJ box.

    This is not a good/permanent solution, but sometimes a three prong to two prong adapter does the trick.

  10. I too think the cause is likely a ground loop. That means your equipment is grounded in two places, the connection to the PA closes the circle. That circuit circle captures the magnetic field from the AC power and converts it into electricity. Not much, but enough to be audible in the sensitive audio input, as hum. The larger the surface area of that circle, the louder the hum.

    So disconnecting the ground on one piece of equipment not only solves the problem, but it doesn't make it less safe because the equipment is still grounded. You just disconnect the surplus of ground connections.

    • "So disconnecting the ground on one piece of equipment not only solves the problem, but it doesn’t make it less safe because the equipment is still grounded. You just disconnect the surplus of ground connections."

      You couldnt be more wrong or dangerous!

      Removing the safty ground from one bit of kit may break the loop but it WILL make that bit of kit dangerous. If you have a fault with that bit of kit and live goes to chassis you WILL be electrocuted!

  11. I had the same problem a while back. Did a bit of research and ended up buying a ground loop isolator. Only cost me about £8 off ebay and it sorted the problem straight away. I've bought another since to stop the hum from a few other connections so I don't have to keep unplugging stuff. I have one on headphone jack (from computer) to phono, which I use to connect my computer to my mixer for just general listening through my dj monitors and phono(from external souncard) to xlr for producing on my KRKs. They really clean up the sound and its a simple solution

  12. totaly agree with 'bbryte' and 'dj willi',,, thats what i did .i actually replaced the laptop cable with and old stereo 2 pin cable (no ground).
    most laptop power adapter have a universal connection so replacing the cable is pretty easy.
    works fine for more then 6 years now...

  13. Chris Argueta says:

    DO NOT LIFT THE GROUND (also known as: removing the ground prong).

    Use an Ebtech Hum-X on laptop's power supply power plug.

    Still have a problem? (You shouldn't if you're using the Hum-X)

    Use a ground loop isolator for all of the channels leaving your sound card. This is a ground loop isolatgor:

  14. With my laptop live rig I'm using balanced TRS cables which are fine with my KRK's at home but when i plug into a Mackie 32/8 at the studio/live there's that loud hum again! Must be honest I was not expecting it as all connections are balanced. I don't really don't to go down the un earthed route but seems my only option after a days searching. I've got a ground loop isolator but that's only got RCA connections so NFG.

  15. john shaw says:

    To solve the static noise when on charger issue get a 2 pin equivalent (NOT cloverleaf type mains connector) charger to solve the problem safely and cheaply, (you can even get them for Dell's...Grrr) the problem is caused by the earthing of the 0v (DC) pin (on 3 pin chargers) and then using the PC with any audio equipment that is then also referenced to the same 0v line..i.e earthed amplifiers,mixers etc. You could use a "fully floating" (as opposed to balanced) 1:1 transformer if you've got one handy. Ebay has these, just ask the seller if 2 pin or 3..hope this helps someone.

  16. Be sensible about this people, removing the earth from a plug is not only dangerous but if you have a fire it WILL invalidate your house insurance!
    There are a few ways to resolve this issue WITHOUT making equipment dangerous, if google around you will find plenty of info on resolving this.
    If you are going to "lift a ground" make sure its on the audio cables, NOT THE MAINS CABLE!

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