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Noise!! AARGH!

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  • Noise!! AARGH!

    OK, so I finally did some more troubleshooting on my carpc to find out where the source of the noise is coming from.

    The noise is basically like faint white noise which doesn't really change with RPMs, it's just static and annoying when music is low or not playing.

    BTW, this noise occurs anytime the RCA is plugged in from the carpc to my amp. The noise comes from my speakers, obviously.

    I found out that the cause of the noise is both my carpc's power cable (via an ITPS mind you) and also the VGA cable when the LCD is plugged in. Nothing even needs to be on (LCD/carpc), it just occurs when the engine is on.

    So clearly the engine noise is coming in from +12v. But why is it going out through my amp and not somewhere else? Do I have a crappy ground somewhere? My carpc is grounded to the same place my amp is, and it's a pretty good ground (4awg with a huge ring terminal and the ground point was filed/sanded to bare metal). I also tried adding a chassis ground to the carpc case, but no luck.

    Or maybe my sound card needs to have an extra ground added? If so, where? I have the Audigy 2ZS. I should probably try the Via M10000 native audio out and see if they, too, exhibit this noise.


  • #2
    I'm pretty sure its a problem with the ground somewhere, make sure everything is grounded properly.

    Originally posted by sq_geek
    The noise is basically like faint white noise...
    I never knew noise had colors, must have been smoking the good stuff when listening to the noise. j/k
    Asus A7N8X-VM - AMD Mobile Athlon 2400
    512 Ram - 60GB HD - Opus 150w
    Lilliput 7" - Rikaline 6010
    [00000000000001100010-] 98% Completed

    Check Out My Install!!!


    • #3
      Ok, so let's assume it is a ground issue (I hope it is, cuz that means I'm close)...

      Would the issue be the ground for the source of the noise (LCD or ITPS), the sound card/chassis or would it be the output device (Amplifier)?


      • #4
        White noise

        Just to define

        White Noise - Acoustical or electrical noise of which the intensity is the same at all frequencies within a given band.

        just a little different than

        Pink Noise - random white noise that has been adjusted so there is equal energy per octave

        which is used in the audo field for tuning and testing and what not.

        carry on.
        ** Denotes an "in car" post
        In-Car posts made from passenger seat - Be safe, Don't Post and Drive.


        • #5
          are u using the lilliput egg adaptor to power the lcd?


          • #6
            i am, why do you ask. can this cause the noise?
            MII 6000; 256 MB; lilliput touchscreen; 40GB; bluetooth SE 68i; software still experimenting switched from mediacar to frodopayer, phonecontrol, destinator 3 (NM), and others.


            • #7
              I am not.


              • #8
                Mine caused alot of noise. I could cup it in my hands and hear the noise go away. When I opened them up the noise came back. So I got rid of it and now power the lcd from the opus.


                • #9
                  I had the same problem when I was using my Xbox-Linux in car setup. I attached a seperate ground cable to the metal chassis of the Xbox and it went away.

                  If your carpc is not powered using a UK-style plug which has 3 wires including a seperate ground wire (i.e you have a power cord like the Xbox with only +ve and -ve) it's not getting a good enough earth. Put a grounding strap/cable from the chassis of the computer to the body of the car. Solved all my problems - no hum or interference.
                  -= Supra Twin Turbo MK4
                  -= Lotus 7 replica
                  -= Escort MK1 with 2.0 16v XE
                  -= Xbox-Linux-in-car-system (v1)
                  -= EspressoPC, 256Mb, 40Gb, WinXP (v2)
                  -= Pioneer AVHP6400 6.5" headunit, MEHP9100 MD/CD, CDXP1230, Infinity Reference 605cs/6502i & 2x RA7502


                  • #10
                    id idnt read all the replies,, not enough time... but ground your VGA shielding cable,, solder a piece on that *****,, then ground it,, itll do wonders,, just watch
                    throw a moon

                    heuvos vin chevos


                    • #11
                      It's not just my VGA - it makes this sound even when only the power is hooked up.

                      So I spent the last hour or so troubleshooting this some more. I experimented with adding a ground direct to the battery from a variety of locations. Still won't go away. It didn't even reduce slightly, this sound is just not budging. It's kind of like a static noise which matches the clickings from my engine ( = engine noise).

                      So I'm really getting frustrated with this now.. I have no idea what is going on.

                      One thing I noticed while poking around with my voltmeter.. When the computer is plugged in (note: NOT on just plugged in), I see ~5vAC (yes AC) between the chassis and the common ground points. I see the same on my amplifier's RCA cables (which makes sense since they are basically connected to my pc). But when I unplug my pc's power supply, it goes way up to like ~ +100vAC easily (I didn't really look how high it went).

                      What is causing this?

                      Where else can I test ground points to get rid of this noise? I tried my pc case (sanded a spot), my pc's psu ground lead, my sound card mounting screw, etc..

                      Any ideas???



                      • #12
                        Put a 47.000 uF 25V (min.) capacity plus 10 capacity of 10 uF all togheter in parallel to your supply line.

                        You should resolve the problem! ;o)

                        Bye bye, paperinics!


                        • #13
                          That would basically be a separate battery for the PC, no?

                          I have a feeling something is not right and that would just be putting a band-aid on the problem..

                          If it is a ground issue, how can I tell if my grounds are "good" ??


                          • #14
                            no, those Farrad values are way too low to be considered a seperate battery for the pc, however i am not so sure that doing that will fix your problem.

                            what got rid of my noise problem was completely ungrounding my motherboard from the PC case...
                            CarPC install is starting to come along again...


                            • #15
                              For me it worked well... all noise was killed! It was mainly introduced into the power line by the Lilliput 8" touch screen, when the engine was running...

                              I'am quite sure that this capacity trick should remove or attenuate your noise.
                              Putting a big capacity plus some minor capacity in parallel will decrease the internal resistance of the toal parallel capacity permitting a better filtering!

                              Just try ) capacity doensn't cost too much!

                              bye bye, Mauro.