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  • YANT (Yet another Noise Thread

    Help!!

    I just added a high-power amp to my setup and now I get noise added to my
    running setup.

    My question. As the amp is in the back, the plus is connect to the battery, the minus to the chassis.
    Since the HU is up front, I am assuming that it too, is connected to the chassis. I have solved noise on my setups before by connecting ground to the chassis, do I also have to connect the HU to this ground point. I do not want to use a GL isolator, I have had them before and they cut off highs and lows in addition to ruining stereo separation.

    o/______\o
    (oo_OO_oo)
    []o-----------o[]
    '94 320i


  • #2
    then youll need to either reground your radio, your amp, or reroute your RCA's. these are the three most common sources of alternator whine.

    the groundings are more than just a quality ground, too. It has ot be a ground thats free from interferrence, just like the RCA's. So if it turns out to be a bad ground, moving it two inches wont cut it. gotta find a totally separate location thats known to be clean.

    Comment


    • #3
      Thanks WhiteRabbit. I'll try moving it this weekend.
      BTW
      The common Ground principal. Does this apply to the positive connection as well?

      o/______\o
      (oo_OO_oo)
      []o-----------o[]
      '94 320i

      Comment


      • #4
        thats a good question. I dont have a universal answer for you, but I can tell you what I do know for sure.

        it does matter, but in my experience only with respect to cable routing. Its generally an accepted fact that routing RCA cables next to the power wire can lead to induced noise, due to the amount of currrent flowing through the power wire. an equal amount of current flows through the negative "wire" as well! this is how dirty grounds are created. power flows through teh chassis of the car in the path of least resistance (duh). So, if the path (we can think of the path as wire sized) happens to cross teh RCA cable path, then we have the chance to induce noise in the system through the ground wire.

        The reason it happens in many cars without stereos, is because there is a ton of stuff in the car that draws large current besides aftermarket amplifiers. Your fuel pump is a great example. if you have an install that you know for a fact is getting induced noise through the RCA cable rather than from a dirty ground, you can lay the cable across the fuel pump, and youll get noise. that fuel pump also draws current all the way from the battery! so any point along that ground path might cause noise too. It can be a royal pain to try to figure out where a theoretical clean ground is!

        In the shop, we would always just make a note of it when we found a clean ground. the only one that comes to mind is the steering wheel shroud mounting points on a toyota sequoia. we never had noise issues grounding to that, so when we got one of those cars, we just always used that as a grounding point.

        so, ground or positive wire, its the same idea......

        Comment


        • #5
          Regrounding your head unit is generally a good idea. When the HU's get installed, usually you connect the ground as part of the wiring harness, and it goes to the universal ground in the car. I know, in mkII MR2s atleast, that this ground is absolutely worthless.
          Carputer Progress Meter
          {[|-------------------]} 5%
          Research and planning.

          Car: 1991 Toyota MR2 Hardtop
          Stereo: Planet Audio TT4300 & TT1250D, Kicker Resolution RS6 (front) & RS5 (rear), Image Dynamics IDQ12V.2 D4 (2x), Sony CDX-M610

          Comment


          • #6
            Originally posted by WhiteRabbit
            thats a good question.
            The reason it happens in many cars without stereos, is because there is a ton of stuff in the car that draws large current besides aftermarket amplifiers. Your fuel pump is a great example. if you have an install that you know for a fact is getting induced noise through the RCA cable rather than from a dirty ground, you can lay the cable across the fuel pump, and youll get noise. that fuel pump also draws current all the way from the battery! so any point along that ground path might cause noise too. It can be a royal pain to try to figure out where a theoretical clean ground is!


            ....
            I think you may have something there. The noise that plagues me does not rise with the motor rpm ergo, I surmise that it is not coming from the generator (lichtmachine here it is a steady sound ..can be the fuel pump.. anyone know which side the fuel pump cables route on an E36?... My next step was to get a heavier shielded RCA cable (I think one of the first cables are rather inexpensive). Thanks Guys for all the advise. I shall try several things and report back if you're still interested.. GREAT FORUM!!!!

            o/______\o
            (oo_OO_oo)
            []o-----------o[]
            '94 320i

            Comment


            • #7
              I got it!!! it was a cheap RCA cable pair. Never, Never go cheap on wires.. I'm looking at least a 3 hour job to remove and re-install a proper cable.

              o/______\o
              (oo_OO_oo)
              []o-----------o[]
              '94 320i

              Comment


              • #8
                conratulations on finding a solution!

                Comment


                • #9
                  GREAT FORUM!!! Your're never alone here!! Never, never buy cheap cables...

                  Thanks for the great advise everyone!!!

                  o/______\o
                  (oo_OO_oo)
                  []o-----------o[]
                  '94 320i

                  Comment

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