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Thread: does electromagnetic interference caused by carPC are possible ?

  1. #1
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    does electromagnetic interference caused by carPC are possible ?

    Hi ,


    I looking to find if I have the cleaner signal as possible between source and amplifier because I heard just a little few noise ( which is for me a normal thing ) but next I open my VST host or VLC I can clearly heard a bad noise even if I have desactivated all the useless device of the sound card ( a Xonar HDAV ) .

    I even tried to unplug the RF mouse transmitter but it is not it .

    Is it a software problem or a hardware I don't know but there is only one thing which make me feel there is an hardware problem : when I turn ON the carPC it jams my smartphone FM radio .

    Is it the same signal which cause the noise in the amplifier and the FM jamming ???

    I use Audimulch but still searching for another ; "VSTHOST" don't work very good .


    Thanks by advance

  2. #2
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    I definitely have a parasit problem ; whatever is the PC volume I get a buzz only when I do an action :

    - for example just using the mouse to create a framework ( the square you create to get multiple files or folders for "drag and drop" ) even if there is no objet in the framework ( I just create the framework over empty areo of destop )

    - another example , if I launch a large search on disk like just one letter which make the search very long , I have the buzz very strong but I use a SSD so there are no mecanical parts .... and next the search is stop the buzz stop

    tomorrow I will test with OCCT to see if it is the hard drive which cause the buzz or CPU % but it is very strange .

    I'm not lucky because Audiomulch cause a massive buzz

  3. #3
    Maximum Bitrate Mickz's Avatar
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    Any cable carrying digital data or fast rise time voltages can radiate noise. Everything you describe is common to some degree in most installations unless steps are taken to rectify it.

    Major noise source is the Switch Mode Power supply then the PC and so on, some are worse than others, some are just noise generators.

    1st thing to check is the earthing of components, the PC and PSU earthed to the chassis with very short thick cables, supply to the PSU and LCD should be run straight from the Battery with heavy cables. Good quality Video cable if it’s a long run from the rear of the car, cable dressing by keeping audio cables away from power and data cables on long runs, incorrect earthing and cabling causes most of the noise problems in an average system.

    Some SSD’s can be bad noise generators; others are as quite as a church mouse. A lot of builders use ground loop isolating devices between the PC and amplifier to remove the last of the noise in difficult installations.

    If you search the forums you should find a lot more detailed discussions on noise problems.
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    Sorry , I'm not a spécialist of electronic so when you advise me " the PC and PSU earthed to the chassis " you think about the case or each ground ? I guess it is the second but I prefer to ask .

    I have not earthed the RCA and I use the PC motherboard without case ; just mounted over a plexiglass board ( for the moment because I was not sure which configuration I will definitely use ) .


    With OCCT it doesn't change the noise level so it seems it could be the SSD .

    Only a windows volume change make the noise higher ; it is like if an input was used but they are all diseable except Virtual Audio Cable but it is the same without it .

    Another tips , if I diseable the sound card I get no noise so it is the PC or RCA which are touched ; I hope it is not the Xonar because she is not fixed very well as she is a PCI-E 1X ; I'm furious against the PC standard consortium because the 1X is ridiculously insecured and not deep like old PCI . And I have two card as the 8 output version of the Xonar use an small additional card for 6 output ...

    The most stupefying thing remaining in my mind is to hear the noise moving the mousse or with Audiomulch


    Thanks a lot for yours answers

  5. #5
    MySQL Error soundman98's Avatar
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    search for ground loop

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    ok thanks ,


    Mickz ; when you said "the PC and PSU earthed to the chassis" I understand to earth the ground of PSU but for PC which ground as the 24 PIN ATX is a complexe supply connection ?

    I precise that With OCCT it doesn't change the noise level so it seems to be the SSD as a long search among the disk cause a massive noise .

    Only a windows volume change make the noise higher but even with engine OFF or ON the noise is the same .

    The most stupefying thing remaining in my mind is to hear the noise when moving the mousse pointer ( even with touchscreen instead of mouse )

  7. #7
    MySQL Error soundman98's Avatar
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    Quote Originally Posted by BenTSH View Post
    Mickz ; when you said "the PC and PSU earthed to the chassis" I understand to earth the ground of PSU but for PC which ground as the 24 PIN ATX is a complexe supply connection ?
    you usually only need to make sure that the screw holes of the pc motherboard are grounded-- usually to the same point that the psu uses for ground.


    but you do have a ground loop. i am intentionally vague as there are tons of guides on how to correct that.

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    ok I understand ; firstly I was not aware that the screw holes of the pc motherboard could be grounded and equally I use a distribution bloc for amp and PSU , may it be a wrong option .

    Thanks,
    Last edited by BenTSH; 08-14-2011 at 03:43 PM.

  9. #9
    MySQL Error soundman98's Avatar
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    usually, a distribution block would not affect the power- as long as it can carry enough power to feed both the amp and the carpc.

  10. #10
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    ok ; does a PSU is grounded to the case ; the motherboard can be grounded by its screw but does they should be grounded between them only ( by the case ) or with another ground .

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