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Electrical Issue

  1. Jul 4, 2003 #1
    When I plug my guitar amp into any outlet in my apt. I get a local radio station coming through the speakers in low volume. If I bypass the speakers and use headphones it still comes in so it will come out of any of the outputs.

    Although I have not tested this amp at another place in a long time, I do not believe it to be the amp.

    What electrical mistakes/issues could be causing this?
  2. jcsd
  3. Jul 4, 2003 #2
    Furthermore - are there any common pieces I can add to the electrical cable plug in to stop this? It's something coming through the electrical cable...
  4. Jul 4, 2003 #3
    Make sure the signal ground is isolated from the power ground... otherwise the chasis will act as one big antenna.

  5. Jul 4, 2003 #4
    Can you explain this in layman's terms?

  6. Jul 5, 2003 #5
    You should be using a 3-prong (grounded) outlet, do not use an adapter on your power plug that eliminates the round ground pin.

    Also, you could try using a different length cable between your guitar and the amplifier input. If you can find a shielded cable for this, that would be better.
  7. Jul 5, 2003 #6
    There are usually two grounds in an electronic system. One is for power and one is for signal. The power ground is always noisy, and usually the case of the system is grounded to it. The signal ground is a clean ground. It is used as a voltage reference for the music signal. You don't want this ground to be connected to the power ground. It will cause your signal to be noisy, and it is possible that the case will act as an antenna imposing radio signal on your guitar signal.

  8. Jul 5, 2003 #7
    So entropy - My issue know lies in the fact that when I have my amp plugged through my system to my PC, I get a buzzing in the amp speakers as well as in the PC speakers.

    And when I bypass my computer and just run it to the PC speakers, I don't get the buzz.

    This led be to believe that somehow the cheap mobo soundcard or the computer itself is causing this buzzing, however the buzzing also requires my amp to be plugged into the wall. Weather or not the amp is on or not doesn't matter, just that it is plugged in.

    SO it's like it requires both those things to buzz.

    So I went and got a cheap soundcard to try it. Not only does the buzzing still occur, but when I strum my guitar the monitor get slines on it, and a hard strum causes the monitor to black out and the green light goes yellow for a second.

    So what the hell. Either my computer (not the mobo soundcard) is doing it - or the amp is sending some bad power signals into the lines and distorting the damn computer ****.

    My only guess is to take the amp in to the store. The guy said it didn't sound like my amp was the issue - but i dunno.

    Any ideas? I know it's complicated but I am **** out of luck for answers!
  9. Jul 5, 2003 #8
    Whenever you hear buzzing coming through the speaker, it means you have a ground loop. That is to say that you are grounding your signal electronics with two different grounds in two different places. Since the two grounds have slightly different voltage potentials, there is a DC current passing through your electronics. This current is generating thermal noise.

    What you need to do is protect your computer from your amp by using an isolation transformer.

  10. Jul 5, 2003 #9
    Ok Entropy - thanks alot.... a bit more questions for your smart brain.

    First off catch my other post about this - since I've isolated the issue to much fewer pieces of equipment it may help. Let me know what you think in there as well if you please.

    You mentioned the isolation transformer - since in my other post I show that this issue doesn't need to involve the amp at all, let me know what you think about that.

    Also - the type of cord i use to run the amp to the PC is a large size jack, the 1/2 inch i guess it is.

    Do isolation transfomers fit that? And would they have those at radio shack? thanks!
  11. Jul 5, 2003 #10
    Question: Is your computer properly grounded? Are you using the third grouding prong on the outlet plug? Are you certain that ground of your wall outlet isn't floating?

    All the things you have described so far, in this post and the other, are indications that you have a ground loop in your system. Since, you say that have problems even when you don't plug anything into your computer, I have to wonder if the ground of your computer is floating... that is to say, I have to wonder if your computer is not grounded at all.

  12. Jul 5, 2003 #11
    Ok entropy - I am indeed using the third prong of my computer.

    Originally I had my PC in one of those power strips to a power plug. Instead I tried putting the power plug into the same outlet that the strip was in.

    So this floating issue - is that an issue at each outlet?

    Would it be a good idea to try a different outlet? Or would the floating issue be something that would not change at a different outlet..../
  13. Jul 5, 2003 #12
    Sure, try another outlet. Maybe the wall outlet is floating. If that doesn't work... take two of these and call me in the morning.

  14. Jul 5, 2003 #13
    I will try another one and get back to you.
  15. Jul 5, 2003 #14
    I tried another outlet. Identically the same.

    DX posted in the other column trying unplugging each device to see if one is malfunctioning. Since this is easy to do I will go do it now.

    But I plan on speaking with the front desk tommorrow - I will tell them "an electrician at radio shack told me it could damage my computer". So it will give them a reason to fix it. At least send an electrician to assess the problem!

    Anyhow - with all the ****ing testing I have done I am just gonna suck it up if they won't fix it. It has to be inside the walls....

    thanks fer all the help entropy
  16. Jul 11, 2003 #15
    This sounds like a prime candidate for the problem.

    Crystal, I'm guessing you could probably get a ground tester at radioshack. If it indicates a bad ground, you may need to rewire your house or at least the outlets you wish to use for this purpose.
    ***use extreme caution if you try this yourself***
  17. Jul 20, 2006 #16
    buzzing guitar and computer

    Guitars can pick-up the AC humm from a standard PC monitor and put it thru the signal line. Turn volume all the way down on your guitar or turn off your monitor(s) from the front panel, does this change anything? If you have an LCD monitor forget about what I said. Also, are there any touch lites or flourescent lights in the room, maybe on the same breaker? Does the room you play in have a concrete floor? Bare or under carpet? Are you using any effects? Tuners, pedals etc... if so, and they use wall-wart power adapters, try using a 9 volt battery instead of A/C.
    Last edited: Jul 20, 2006
  18. Jul 22, 2006 #17


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    The do sell isolation transformers for most audio connectors. Radio Shack might not have them, but a good music store probably will.

    All of the items mentioned so far could be causing your issue.
    However, the cure might be as simple as flipping the isolation polarity switch on your amp.
    If it has one.

    Also, you might not need to use the amp if all you are trying to do is get sound in your PC.
    Try an adaptor connector and plug guitar directly into sound card.
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