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Thread: noise w/XP even worse

  1. #1
    Mod - all of it. SapporoGuy's Avatar
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    noise w/XP even worse

    Didn't want to post until i got more details.

    alpine HU (volume 30 max), voompc case, m2atx power, jetway board, xp+cf, pata HD

    My HU with RCA via alpine connector produces normal static noise when I crank the unit up to around 25. If I remember right without the connector basically no noise even around 30.

    Plug in old ipod and have no noise.
    Bench the voompc and have no noise.

    Plug in power and ground lines and connect to HU with RCA cables -- get some noise at around 23.

    Now this gets interesting, I start up my unit and all the way through bios and get a tad more noise than when it's off.

    Once XP gets to the startup screen I get all kinds of static, noise and a beep like pulse noise that matches HD access (verified by watching the mobo blink.

    I have tried:
    battery to m2
    body ground to m2
    body ground to m2 + battery ground to case (reduces noise by about 1/2 or more)
    battery ground to m2 + body ground to case (reduces noise by about 1/2 or more)
    * ground to case refers to the bottom panel, screws to mobo and m2
    I have not run the power straight from battery to m2 yet, I am going through a switch and the molex connectors.
    I have checked and redone connectors that looked skeptical.

    Of course the noise gets worse when I have the car running.

    I have also tried mono plug to jack on back of the mobo and running cables to the voompc mini board that has usb/rca jacks. Location and different cables make no difference.

    err, I even ran ground to the screw on the HD, thinking that the HD might not be grounded right ....
    lolo, I think I fried my XP install again.
    school boy move!!!!



    Ok guys, I'm at a loss what to do next.
    Any suggestions?
    Also, why would XP make things all the worse?

    Thanks in advance!

  2. #2
    MySQL Error soundman98's Avatar
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    i don't think that xp is causing it, but the audio driver that xp loads--once the audio is started, then you get the ground loop..

    you can also try powering the hu from the same power and ground location as the m2, or try grounding the negative of the rca cable...

    you didn't mention whether you sanded the paint off the location that your ground wire is attached to, so i also recommend that if you haven't done it already.

    you could also try to move the ground location for the hu and/or the carpc as well

  3. #3
    Mod - all of it. SapporoGuy's Avatar
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    Thanks!

    I'll go ahead and give the pc+hu suggestions a try.

    grounds are double checked and sanded.

    I too thought it was the audio driver but when I use the pc on my bench I have zero noise and clear audio. Just a tad strange that once the startup screen for XP comes on the unit spews lots and lots of noise and static. Maybe a power consumption difference that makes the original noise worse?

    Thanks

  4. #4
    Mod - all of it. SapporoGuy's Avatar
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    narrowed down my noise problem.

    My lilliput is causing havoc with my system.
    * HU+pc=not much of a problem (grounding to same point)
    * add in the monitor and egad!!! (turn it on makes you want to turn it off asap)
    - been playing with power and grounding ... not much helping.
    ... straight power from battery, using acc / power harness from radio, taping the fuse (all prove horrible)
    ... grounding from battery, same point as pc/radio, separate area (not much of a difference)

    I'm gonna try go straight from the m2atx ...

    any other suggestions?

  5. #5
    Variable Bitrate djvillar's Avatar
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    Quote Originally Posted by SapporoGuy View Post
    I'm gonna try go straight from the m2atx ...
    I was going to say to power it via your smart ATX. Get an extra molex connector. Cut off the one of the black wires and the red wire its next to, thats the 5 volt rail (not needed). Run some line from the yellow and the paired black (this is the 12v rail), put an inline fuse holder for a 2amp "fast-acting" 250v fuse. This is the same fuse you'll find in the cig adapter that comes with the lilliput. Now get a barrel plug size "m" from radioshack (barrel plug and solder that in. There's your power. Things should be more stable that way.

    Good luck.

  6. #6
    Mod - all of it. SapporoGuy's Avatar
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    djvillar,

    Thanks for the heads up! I am glad that you posted because I would never have thought there would be 2 different rails. I did something similar with the adapter but used one off of a unit I had laying around from an old telephone or something.


    Also thanks for the reminder of using a fuse. I probably would have forgotten.

    @update
    By moving my lilliput to the m2-atx power supply I cut my noise basically in half. However, I'm still getting alternator whine from 20/35 on my HU (35 is max).

    aghhhhhhhh

  7. #7
    Variable Bitrate djvillar's Avatar
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    Do you have component speaker that use a crossover? My crossovers were originally placed under the dash near the front speakers and they picked up every once of EMI from anything they could (the fuse box, the ac fan, anything). I then moved them back to the trunk near the amp and just ran two separate wireing for tweeters and mids to each door... Zero noise.

    Where's your pc. The pc itself and component crossovers I find are susceptible to emi.

  8. #8
    Mod - all of it. SapporoGuy's Avatar
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    crossover??? hmmm, now that is an interesting question. I have stock speakers with a alpine HU. The speakers are separates ... I didn't come anything that resembled an aftermarket crossover in my console.

    currently, pc is out of the voompc case and put between the 2 front seats when I'm playing with it right now. Allows me to keep an eye on it and it's in a better location to accidentally short out (xp doesn't like that very much ...)

    The car is a legacy and has like oodles of space to poke around in.

    I tried about 10 different ground points including direct to battery (this made it worse!)
    I also broke down and plugged the pc in with my bench test unit and the system started howling....

    So far the best situation is pc+radio at same ground point. (with other grounds or just 2 seem to make no difference)

    I also tried a few other power sources from the main harness that aren't being used. No luck so I went back to the straight line from battery. Which reminds me, I still need to test HU+pc from the same power ....

    Things to still try:
    ground loop isolator -- have to find one in this country first!!!
    alternator line suppressor (err, whatever it is called)
    ground my pc + atx + case several times over

    Just in case I haven't written already:
    I ran ground cables from HU to rca plugs ...

    Thanks for the input!!!

  9. #9
    Variable Bitrate djvillar's Avatar
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    Quote Originally Posted by SapporoGuy View Post
    ground my pc + atx + case several times over

    Just in case I haven't written already:
    I ran ground cables from HU to rca plugs ...
    Each item should have no more then one ground point. If elec. have more then one way to flow you'll get noise, which is the elec. oscillating from one ground to another creating a wave that will be amplified into sound (noise). So, if you're grounding your rca's which is connected to the head unit and the pc and the amp, and they're all grounded themselves... this might not be the best setup. Also you don't want to ground your board to one location (or multiple locations) and then the case to another. It would be fine to ground you're MB to the case then the case to the car chassis, that creates one path out. Inlets of energy enter the components at different locations but exit using the same one outlet.

  10. #10
    Mod - all of it. SapporoGuy's Avatar
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    Thanks for information.

    I read this yesterday and have been planning how to lay out my grounding.
    KISS method sounds like the best.

    However, I still have figure out were the ground leak is occurring.

    monitor is connected to m2 power and video cable to obvious location.
    pc is grounded to same location as HU, power from battery, connected to HU by rca
    Hu is grounded with pc (screwed into OEM audio frame that's welded to car) and power is from the harness

    I still need to check pc with headphones for noise (bench test is clear)
    noise is obviously introduced with the connecting of rca between pc/hu ..

    gonna keep at it

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