Previous 1 2 Next 22 Replies Latest reply: Jun 19, 2006 1:29 PM by Band On The Run
Jack Q Level 1 Level 1 (20 points)
I know a lot of people on this board are knowlegeable about recording studios and equipment and was wondering if you could help me out.
I record with Logic Pro and a MOTU Traveler into a MacBook Pro. When I am holding my electric guitar when it is plugged into my guitar amp, and I attempt to touch my computer (to start recording, for example) I get an intense static shock. I'm not sure what the problem is, but it might be bad grounding in my room. I was wondering if anyone has experience with this and has an easy way to remedy the problem. You help is much appreciated.

Mac book Pro, Mac OS X (10.4.5), 1.83 GHz
  • Steven von Kampen Level 3 Level 3 (850 points)
    That's because you ROCK!

  • Blumpy Level 4 Level 4 (1,090 points)
    Grounding will follow the path of least resistance. So something is trying to ground though you. Ground lift your amp and probably your traveller too.

    Also, plug everything into the same circuitbreaker if it is, try all into the same jack so the grounding distance is the same.
  • blayzay Level 3 Level 3 (630 points)
    You need to find yourself A gloves and A hard boot, before you attempt to use your setup.
    Get A electrican, and make sure your stuff is pluged into A surge adoptor before you blow stuff up, are hurt yourt yourself.
    I dont want to see you in,
    Safe that is.
  • Jack Q Level 1 Level 1 (20 points)
    Are you serious? This is the only problem I have. When doing anything else with my equipment, besides holding my guitar, I never get shocked.
  • Blumpy Level 4 Level 4 (1,090 points)
    He's right, it is potentially dangerous.
  • xs4is Level 4 Level 4 (2,800 points)
    to you and your computer!!

    And your computer
  • dmacintyre Level 1 Level 1 (70 points)
    Slightly different situation but similar results for me. When I had my 17" Powerbook, I would connect it to my TV with the S-Video cable to watch DVDs. When it was connected, I could feel a constant mild electric current when I touched any part of the metal case of the Powerbook. Not painful but noticeable.

  • Freddie Woolfe Level 4 Level 4 (1,175 points)
    It's definitely that... When I was using my Powerbook in Italy with a continental adapter that didn't support UK grounding pins, my PB 's surface would fell rough, due to the electricity.
    By sorting out your earthing, you will probably notice less hum from your guitar too...
  • tsvisser Level 3 Level 3 (755 points)
    that is likely because you are using a Japanese guitar or Mexican guitar. They have twice the voltage over there and that is translating to extra power on U.S. 110VAC, or the Mexican factory had their power hooked up backwards, and it has flawed the wood veneer so you are getting -110VAC. ...uh, seriously...

    I find that a lot of amplifiers, especially if vintage or of vintage design, are very poor at earthing the signals. I have a silvertone tube amplifier that seems like it transmits a portion of the AC voltage through the instrument line in from one of its primary transformers.

    If because of the equipment that you are using you simply cannot earth ground everything, and even if you do, the source of the voltage is in fact dirty leakage from a piece of equipment, I would highly suggest that you transformer a few key connections. use a jensen transformer (or other high quality transformer) between you computer and your sound gear. because you are using a MOTU that is likely hooked up via Firewire to your computer, you should place the transformer between you amplifier(s) and the MOTU. what this does is electrically isolates your computer rig from your equipment. to protect yourself, you could also place a transformer between your guitar and your amp. you might have to use a separate line driver (preamp) first, as i'm not sure you can or would be pleased with the results of transformering an instrument level feed, would likely have to be line level before it works well.
  • tsvisser Level 3 Level 3 (755 points)
    the TV situation might be different... do you have cable service? see if this stops when you disconnect the cable feed from your box. it is quite common for the cable companies to have an unusually high DC offset from their incoming lines, or a small AC potential on the shield. this happens, even if you aren't watching the cable box, just the fact that it is connected electrically to the system, which is in turn connected to the tv, in turn to the computer, etc...

    if this is true, you can buy a DC block, but cheap ones mess up with the digital portion or "interactive" communication of digital boxes. again, jensen makes some nice transformers that address DC offset from digital cable lines too.
  • jord Level 5 Level 5 (5,230 points)
    Potentially lethal is more the word. I would definitely get the amp checked to see if it has a grounding problem. As some others have stated, some isolation transformers and going off the same electrical circuit can only help.

  • SteveDjokes Level 2 Level 2 (370 points)
    Jord is 120% right..It could B leathal..I heard about at least one guy buying the farm this way...I cannot recall exactly what happened...But I would ASAP Repeat ASAP go to the dealership and state the problem..They'll know and they'll fix it...It is VERY dangerous...Dont fool around with it...I aint kidding..........................!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !
  • Randall Thomas Level 3 Level 3 (555 points)
    When I am holding my electric guitar
    when it is plugged into my guitar amp, and I attempt
    to touch my computer (to start recording, for
    example) I get an intense static shock.


    There may be no solution. It could simply be your electrifying personality. But, barring that....

    A static shock is less indicative of a poor electrical grounding scheme than if you had, as others have described, a constant noticable current when you touched the Macbook.

    As you strum your guitar, you and your rig are building up a static charge which likely has nowhere to go because your amps input scheme doesn't tie your instrument cable shield to earth ground. Even if it did, you and the strings may not be connected to it, so the amps grounding may have nothing to do with it. You may notice it more when you're plugged into the amp because that's when you're "strumming".

    Strumming your guitar and then touching the Mac is analogous to shuffling your stocking feet on the carpet and touching a metal doorknob.

    This is less hazardous to you than it is to your computer and its data. But there is a solution. Check these out:

    Something for the table:

    Something for the floor:

    You can get a mat for the floor that you simply step on before touching the Mac, or you can put a mat on the table and touch it before you touch the Mac. Setting your Mac right on it wouldn't hurt either. The mats provide a resistive path to ground that slowly and safely discharges the static charge. So, no more shock.

    Regardless of what you do, be sure you have a good ground available and that everything grounds to the same place. Hopefully that's 2 copper rods driven into the ground somewhere outside your studio.

    Many products, probably your Mac too, do not have a grounded case. This isn't a bad thing. But, like the doorknob, they can still have enough of their own ground potential to discharge a static charge.

    Good luck Sparky.

  • Band On The Run Level 3 Level 3 (505 points)
    Shocks suck. It is most likely (and please don't be offended) poor wiring on your guitar, OR you have a ground fault in your house wiring where you're plugged in.

    I don't care where you're recording, even on the road, you need to have proper grounding for all your electrical. Go get yourself one of these puppies, and it will let you know if there is a problem with your ground, but also protect YOU and your equipment at a very reasonable price. If you don't go much on the road, get a model higher that has more features and filters.

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