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Thread: Z97 Extreme4 - grounding problem - audio hum when mic plugged in




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    Default Z97 Extreme4 - grounding problem - audio hum when mic plugged in

    I recently installed the Z97 Extreme4, replacing my old P5k board.

    I hear a hum when I plug my microphone in. The hum goes away when I touch the case of my computer.
    The hum is louder when plugged into an UNGROUNDED plug power. - So much so that i'm unable to record with mic.'
    There is no hum at all when mic is NOT plugged in.

    Firstly is this hum damaging to the motherboard?
    Clearly there is some electricity going into my case - and I'm not sure if that is normal or not - I'm not feeling too happy about it though ;)

    Secondly, I'm wondering if this is related to bad assembly on my part. Perhaps anything to do with the "back plugs"? (I mean the small plugs; that the screws that fasten the motherboard to the case go into)
    - Could I have 'missed' one of those as I switched motherboards? Or wouldn't this matter? Are these the only 'metal connections' between MB and case? )

    Thirdly, does anyone have a solution or has encountered this before?

    Thanks!

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    Default Re: Z97 Extreme4 - grounding problem - audio hum when mic plugged in

    I had the same problem with x79 and W8.....try update BIOS
    Hope thai helps
    Best
    Quote Originally Posted by ocoini View Post
    I recently installed the Z97 Extreme4, replacing my old P5k board.

    I hear a hum when I plug my microphone in. The hum goes away when I touch the case of my computer.
    The hum is louder when plugged into an UNGROUNDED plug power. - So much so that i'm unable to record with mic.'
    There is no hum at all when mic is NOT plugged in.

    Firstly is this hum damaging to the motherboard?
    Clearly there is some electricity going into my case - and I'm not sure if that is normal or not - I'm not feeling too happy about it though ;)

    Secondly, I'm wondering if this is related to bad assembly on my part. Perhaps anything to do with the "back plugs"? (I mean the small plugs; that the screws that fasten the motherboard to the case go into)
    - Could I have 'missed' one of those as I switched motherboards? Or wouldn't this matter? Are these the only 'metal connections' between MB and case? )

    Thirdly, does anyone have a solution or has encountered this before?

    Thanks!

  3. #3
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    Default Re: Z97 Extreme4 - grounding problem - audio hum when mic plugged in

    Quote Originally Posted by ocoini View Post
    I recently installed the Z97 Extreme4, replacing my old P5k board.

    I hear a hum when I plug my microphone in. The hum goes away when I touch the case of my computer.
    The hum is louder when plugged into an UNGROUNDED plug power. - So much so that i'm unable to record with mic.'
    There is no hum at all when mic is NOT plugged in.

    Firstly is this hum damaging to the motherboard?
    Clearly there is some electricity going into my case - and I'm not sure if that is normal or not - I'm not feeling too happy about it though ;)

    Secondly, I'm wondering if this is related to bad assembly on my part. Perhaps anything to do with the "back plugs"? (I mean the small plugs; that the screws that fasten the motherboard to the case go into)
    - Could I have 'missed' one of those as I switched motherboards? Or wouldn't this matter? Are these the only 'metal connections' between MB and case? )

    Thirdly, does anyone have a solution or has encountered this before?

    Thanks!
    Microphone hum is common, and is normally not caused by a voltage accidentally applied to the chassis/case that has the microphone input.

    Which microphone input are you using, the one on the board's I/O panel, or a microphone input on the PC's case?

    If it is mic input on the PC case, then the cable running to the audio input on the board may not be grounded correctly.

    If the hum stops when you touch (ground/earth) the PC case, you can ground/earth the case with a piece of wire connected to the PC case (bare metal spot) with a screw, and the other end connected to the screw that holds the cover plate on the AC wall outlet.

    Are the "back plugs", or mother board standoffs, you are using black, or a metallic bronze color? Are the screws used to hold the mother board black or bronze in color?
    If they are both black, which is paint, and are quite commonly supplied with PC cases, they may be not grounding the board to the case correctly. Mother boards have solder points around the screw holes on the top and bottom of the board. They are ground points for the board, although the PSU has many ground connections between the board, PSU, and AC ground. The paint on the standoffs and/or screws will insulate them from the board, and not ground the board to the case through the screw hole ground points.

    Whether or not the ground points around the screw holes must be grounded to the case is a question I can't answer.

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    Default Re: Z97 Extreme4 - grounding problem - audio hum when mic plugged in

    Both front panel and I/O panel gives the same hum.

    Last night I removed the motherboard to check all screws and standoffs(ty).
    The motherboard standoffs are in a bronze color - the screws are metallic (not painted), same type of screws used all over the pc.

    They look like this: http://www.pcityourself.com/images/c...oardScrews.jpg

    (I noticed the MB has 7 screw holes - I have only got 6 standoffs.(and use 6 screws to fasten) The missing standoff/screw is slightly low,left and to the center.))

    Perhaps the first thing I should do is look into acquiring some of the screws you mentioned?

    Thanks for the wiring guide you mentioned, ill look into that as well - but maybe I should get an electrician for that. My apartment is very lacking in grounded power outlets to begin with - so would be good to have more of those anyways. The distance from where I have my PC and a grounded outlet is 5-6 meters - so PC has been plugged into an ungrounded outlet for years..

    See if I find some new screws first. Thanks for the replies

    ((oh, you meant the screws should not be 'painted' .. so my screws are all right then..?
    Last edited by ocoini; 06-12-2014 at 01:42 AM. Reason: screws

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    Default Re: Z97 Extreme4 - grounding problem - audio hum when mic plugged in

    Yes, unpainted screws so they are not insulated, the standoffs and screws you have are fine.

    If the AC outlet you use is not grounded, that may be the main problem with the hum you get. If you used the same outlet with the other board, clearly something has changed related to the new board.

    Check the plug and cable on the microphone, it might have lost the ground connection for some reason. Do you have another microphone you can test?

    Did you check in the audio configuration software for your board, if the microphone inputs are configured as such, not set up for another purpose. That is a rare feature some boards have. Check the levels, etc, for anything that is not right.

    Your hum problem might be related to the change in mother boards, and with it the change in audio circuitry compared to the other board. Such as, the input impedance or sensitivity of the microphone input is very different on the new board, and is not compatible with the microphone.

    Your previous board seemed to have a different or better grounding configuration than the new one. If the case is the same, can you identify any changes in the cables between the PSU and board.

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