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Thread: need some noise help

  1. #1
    Variable Bitrate spyhunter's Avatar
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    need some noise help

    ok i have an aftermarket headunit with rca outs and the computer with a 1/8in to rca cable.

    the both lead to an rca switch box which then goes directly to a 5 channel amp.

    when listening through the stock headunit, there is no noise at all. when listening thought the computer i get horrible noise. so i put a filter on the computer line, it corrects most of the noise however it kills the sound quality (lows and highs are cut off).

    with the filter in place, there still is a lot of static coming through the system and moving around the rca does not cure it.

    setups i've done to help correct the problem....
    the computer's 12v PSU gets its feed directly from the battery with a relay inbetween (the relay is switched one from a power lead from the stock headunit, acc) then to the PSU. it is grounded to the same spot as the amp.

    i've also tried a usb sound card with the same resulting noise and static.

    note: i had this exact setup in my old car and had no noise problems at all. well the wiring was a bit different, power routing was the same accept rca's from the factory headunit was wired much differently.

    what else can i do/try to fix it? i think i'm gonna return my usb sound card and get something better perhaps...maybe the extingy. any recommendations?
    Alex
    90 300zx twinturbo conversion
    Epia C3, 512 ram, syntax mobo, 80 gig WD, Mediacar, GPS w/Routis, all behind drivers seat, 7in Lcd Lilliput VGA with Touch, wireless adapter for stumbling, Consult ODB1 adapter and data scanner.

  2. #2
    FLAC bosstone74's Avatar
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    try regrounding in some different unpainted areas...
    BossTone74

  3. #3
    FLAC guitar333's Avatar
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    yeah try to use seperate grounds and see if that helps
    92 Taurus SHO - Daily driver - Epia M10000 80GB 512mb 7" touchscreen, Opus PSU etc

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    90 Silver SHO - 419whp fun/project car, CarPC to come (for tuning)

  4. #4
    Constant Bitrate
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    Have you taken a reading on the voltage difference on the grounds between pc and amp to get an idea of how much noise is there? When I did my quick and sloppy test install I had a 47v difference and the ammount of noice was hilarious. After a nice 8 guage copper speaker wire for ground I tested again and got 36mv. Sound is only there if you turn up all the way and don't have audio playing. Good luck.

  5. #5
    Maximum Bitrate osirisdon's Avatar
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    Have you tried to get your accesory 12v from another location, example directly from the battery "for testing purposes?

    You also mention a RCA switch box, that sounds kinda fishy. Try eliminating that switch, and go directly to your amp with the computer.

    What kind of noise is it? The "rev whine" or some type of static noise? Also what kind of pc are you using? Does it happen with specific players only or just the PC in general?

  6. #6
    Variable Bitrate spyhunter's Avatar
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    i'll do some testing with different grounds eventually...changing the clutch has priority right now

    it is not alternator whine...mmm i'll make a recording of it and post it when i get a chance, its horrid. my website has the details on the computer...its an epox motherboard with onboard sound...
    www.mattoree.com/z
    i get static and a constaint high pitch sound with the filter, without the filter there is more noise than i can recognize included alternator whine and what sounds like the cooling fan on the cpu
    Alex
    90 300zx twinturbo conversion
    Epia C3, 512 ram, syntax mobo, 80 gig WD, Mediacar, GPS w/Routis, all behind drivers seat, 7in Lcd Lilliput VGA with Touch, wireless adapter for stumbling, Consult ODB1 adapter and data scanner.

  7. #7
    Variable Bitrate spyhunter's Avatar
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    ok so i did some more tests tonight and i think i have most of it solved.

    1. the rcas from the head unit are picking up noise from the lcd invertor whose power lines run right next to it. only the right side ironicly... when connected it unfiltered to the rca box it effected all the inputs with noise, connected with the filter it just gets the invert noise.

    2. the audio out jack on the motherboard is on the fritz if i wiggle it the sound cuts in and out.

    3. i also tried a different rca cable from the computer to the rca box and that cured part of the noise as well.

    something that still erks me is that the sound quality is so much different...it sounds like it needs a strong bass and treble increase. it is not going through a filter of any kind now. any pointers on this? there are no software adjustments that can be made accept through winamp's eq
    Alex
    90 300zx twinturbo conversion
    Epia C3, 512 ram, syntax mobo, 80 gig WD, Mediacar, GPS w/Routis, all behind drivers seat, 7in Lcd Lilliput VGA with Touch, wireless adapter for stumbling, Consult ODB1 adapter and data scanner.

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