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Thread: Question about power wire interference

  1. #1
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    Question about power wire interference

    I think I may have some trouble with interference. My set up is going to include a couple amps and then my computer will be built into the glovebox on the passenger side. I will be running 4ga down the driver side to power the amps, and from what I hear, I need 8ga to power an opus. I will have 3 sets of RCAs 1 pair for each amp and then one set coming from the onboard sound of my motherboard into the AUX of my cd player, which will need to be run down the passenger side(to avoid the 4ga power wire)

    Since my computer is in the glove box and I'll need to run all sets of RCAs behind the dash to get to and from the passenger side of the car, I can't see any way to avoid the 8ga power wire going to the opus, especially the set that is coming from the computers line out.

    What are your guys' thoughts on this.

    Thanks,
    Mears

  2. #2
    Maximum Bitrate Snootch's Avatar
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    What will determine the gauge of wire you need to run to the Opus is determined by the distance from the battery. if you were putting the computer and powersupply in the back of the car, you would probably want to use 8ga. wire feeding the Opus from the battery, because using a smaller wire that long would result in a voltage drop. You would see maybe 11 volts in the trunk due to the resistance of that 12-10 gauge run to the trunk. BUT you seem to be locating the computer and powersupply in the dashboard. You've got maybe, what, 6 feet or less to the battery? i don't think 8 Gauge wire is really necessary. Since the distance is short, use 10 Gauge wire. Make sure you also fuse it within 8 inches of the battery terminal also. The main thing you will have to pay attention to in order to prevent noise will be your grounding.
    1. Make sure your ground wires are the same gauge as your power wires.
    2. Make them as short as you possibly can.
    3. Ground to an area free of rust, paint, grime. CLEAN METAL CONTACT.
    4. Best ground connection is made Like this:
    Attached Images Attached Images  
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  3. #3
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    Thanks. I'm still curious if having two different ground points will be a problem and if I'll run into any problems with interference on my RCA cables from the power wire to the opus.

  4. #4
    Maximum Bitrate Snootch's Avatar
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    Try to run it like you want to, and test it out. Should you have problems, check the integrity of your grounds, and then try to connect both devices at the same ground point. Then check your RCA's and make sure theyre okay, and lastly, try a ground loop isolator. but try all of the above first, as the GLI is just a band-aid.
    See these similar threads:
    Whining/Ground Loop
    Audio Distortion/Interference

    Good luck on your install!
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  5. #5
    Low Bitrate jdaniels's Avatar
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    Quote Originally Posted by Mears
    Thanks. I'm still curious if having two different ground points will be a problem and if I'll run into any problems with interference on my RCA cables from the power wire to the opus.
    2 different grounding points shouldn't do much. Unless one of them isn't grounded good. The metal of the chassis is all connected directly.

    Make sure your ground wire isn't ridiculously long in length...

    I had a huge problem with a nasty ground loop on my carputer, then I installed a ground loop isolator in-line with my soundcard. No more noise!

  6. #6
    Maximum Bitrate Snootch's Avatar
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    You would have a difference in potential between two grounding points on the car, if one ground was to a solid, chunk of metal on the frame, and the other was grounded to a panel welded to another panel,then welded to the frame. If one or more of those welds are bad, resistance will go up enough to cause a ground loop.
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  7. #7
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    use a seprate wire to ground the cases (using the case screws) of each componet to one another (do not ground this wire just go from case to case), this is to be done beside its seprate grounds, daisy chaning the cases helps alot. using realy good rcas twisted pair with a thick shield is a good idea, power can be as long as you want but try to keep it a away from any wires even facotry if possible. ground should b no longer then 24" if you can help it.

    almost forgot i know theres a company out there that makes cat5 into a RCA it has a reciving head and out put unit with rca connnections

  8. #8
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    I'm not sure I understand what you are referring to when you say to ground the "cases".

    My computer is going to be a Epia M10000 mounted on a piece of plywood.

  9. #9
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    Case groundin "common grounding"

    Your car stereo has a metal case, all your electrical componets inside in one form or another also ground to that case. This also goes for amps, Eq's, Computers Etc.

    The stereo, computer etc. cases or frame or Metal box, cover, what ever you want to call it has a screw(s) that hold it together.

    un-screw one of those case screws, terminated a ring terminal to the end of a wire put the screw thru the ring terminal and screw it back to the case. At the end of that wire do the same thing to your next componet and from that componet make another wire and do the same as above to the next componet.

    Some times its not possible to ground all your componets in the same place, sensitive ones can create noise, due to a many number of problems but normaly all from the same effect GROUND LOOP the elussive hum. weak welds, rust, bad componets, back feeding etc also create grounding to be weak in some areas. running a wire from 1st componet (head unit) to your last comonet (amp) assures they have some common ground. Doesnt always work but helps and for the most part is a good idea for many other reasons.

    Enough of my babble, i found this sight pretty well writen and alot of people here asking and answer these type of questions should read it.
    http://www.epanorama.net/documents/g...oop/index.html

  10. #10
    Constant Bitrate gubon13's Avatar
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    Quote Originally Posted by Snootch
    4. Best ground connection is made Like this:
    Just out of curiosity, is there a reason why the split washer is on the bolt side of the panel, and not on the nut side? I always thought it was supposed to be on the other side.
    "Is Wayne Brady gonna have to choke a b@$#*??!!"

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