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would a VGA "amplifier" solve LCD hum??

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  • would a VGA "amplifier" solve LCD hum??

    hey guys. i'm tired of not being able to solve the noise problem in my car, so i decided to just hide it. so i was wandering. has anyone tried using an active vga splitter or amplifier, to "Clean" the signal? do you think this will work??
    also, if my vga-card had an HDMI (it does not), would , hooking a hdmi to vga converter solve it??

  • #2
    You need to describe the noise.
    link to my CTS-V project:

    http://www.mp3car.com/worklogs/153699-a-macd-v.html

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    • #3
      the classic hum. its preiodic, with some spikes now an then, but, it gets stronger with longer vga cable. 1.8 meters, and i have no noise. add enother 1.8 , and i got enough noise. 5 meters are noisy as ****.
      although i dont know if it is the same noise, but in the speakers, you can hear noise that has its peak at 1khz , and goes up with my RPM (2000rpm = 2khz and so on... )

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      • #4
        Sounds like alternator noise to me.
        link to my CTS-V project:

        http://www.mp3car.com/worklogs/153699-a-macd-v.html

        Comment


        • #5
          Certainly signal degradation - ie, decreasing S/N ratio. But whether it's loss of signal thru the cable or induced noise....

          A better cable may solve it, or maybe suppression caps or toroids, or even breaking of the shielding at the LCD end.
          Otherwise an amplifier may be required, but more info or investigation is required.


          CORRECTION... - corrected "...breaking of the signal GND (maybe shielding) at the LCD end." to "...breaking of the shielding at the LCD end."
          Last edited by OldSpark; 08-18-2013, 08:16 AM. Reason: CORRECTION...

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          • #6
            well. i opened both cables i've been using . 5m (LOTS of noise) and the 1.8( clasic blue vga cable wich comes with new LCD. NO NOISE at all, (if it is alone) ) .

            both seemed to be exactly the same from the inside. what troubles me, is that you cant really "Cut the shielding of the isolation"... the rgnd,bgnd,ggnd, are all striped inside smaller insulations, that in turn, touch the cable insulation. so in a way, it is just ALL the grounds are connected together, with the shielding... any idea if it has anything to do with the noise??

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            • #7
              so i was thinkink. what if i cut ALL the grounds from the vga cable?? will this be bad?? also, if i cut them. do i ground them somewhere else on the chasis, or do not cut them at all?

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              • #8
                Sorry, I meant the shielding - not the signal grounds (they are required).

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                • #9
                  well, shileding is sorted with the signal grounds, in all the cables i have seen so far so... :/ . tommorow i will try to make a cable with CAT5 cable. see how this goes otherwise i will buy an amp!

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                  • #10
                    What do you mean by "shileding is sorted with the signal grounds"?
                    Either the cable has a shielding sleeve or sleeves, or it doesn't.

                    "Analog" cables usually have shields whereas "digital" cables like Cats 5 & 6 may or may not have shielding. (Yes, I know there is no such thing as digital transmission and that analog & digital maybe somewhat arbitrary as asigned to cables.)

                    Do you mean that cables with twisted pairs tend to "cancel" noise? If so, I understand what you mean, but that is not "shielding".
                    Apparently most Cat 3 to 5 or 6 cables are unshielded though I almost exclusively used shielded Cat 5 & 5e etc - not that I/we terminated the shield(s).
                    And I know that for digital comms, if the (Cat 5 etc) shield is used, then it "must" be continuous and that that may contradict noise elimination methods in analog systems (ie - discontinuous shields).


                    Not that I want to get into the subject of shielding etc, but just in case you confuse (multiple) ground wires with shielding and might therefore overlook a good solution.

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                    • #11
                      [QUOTE=OldSpark;1496322]What do you mean by "shileding is sorted with the signal grounds"?

                      i mean that, each of the 3 signal cables, has its ground twisted around it (un-insulated), and in touch with the "shield sleeve" wich in turn, touches the overal shield sleeve. i know that those sleeves are suposed to conduct only from one side, but if you mesure resistance across the 15 pins, you will see that all the grounds, have resisstance to one-enother (meaning they touch), and all have resistance with the shield...

                      i have read that CAT5 is better for longer distances, (maybe cause of the solid cooper inside??) , than a normal VGA cable. and yes its not shielded, nor do i think that the twisted cables will do everything about the "noise". i just wanna check if, properly insulated grounds, and maybe better quallity cable has to do anything with the signal degradation.

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                      • #12
                        That IMO sounds like crap cable. There is little point having grounds (and shields) touching each other when the interface and connector keeps them separated.


                        Anyhow, the Cat-X will certainly preform better than that (as might a "proper" video cable).

                        Cat-x is better because of its twisting method which tends to cancel noise - including what one conductor induces into the others (which builds up with increasing length unless "cancelled").

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                        • #13
                          There is a BIG difference between CAT5 and VGA cable.

                          CAT5 relies on twisted pair and differential for noise cancellation whereas VGA is shielded (for noise) and single ended.

                          A "good" VGA cable has each video signal individually shielded and then wrapped with an overall ground.

                          Most CAT5 cable is several twisted pairs and a ground.

                          Reference this:

                          http://www.dougburbidge.com/vgaovercat5.html

                          Some more info:

                          http://answers.yahoo.com/question/in...8230023AAfh3mY

                          The bigger the resolution, the more noise you get.
                          Last edited by heavymetals; 08-18-2013, 04:36 PM.
                          link to my CTS-V project:

                          http://www.mp3car.com/worklogs/153699-a-macd-v.html

                          Comment


                          • #14
                            well. vga over cat5 certainly did not solve anything >_>. in addition to the noise, it has some extra distortion in picture (shadows or something like that, behind the icons. ghosting i it's called)
                            Last edited by settra; 08-19-2013, 10:15 AM.

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                            • #15
                              Originally posted by settra View Post
                              the classic hum. its preiodic, with some spikes now an then, but, it gets stronger with longer vga cable. 1.8 meters, and i have no noise. add enother 1.8 , and i got enough noise. 5 meters are noisy as ****.
                              although i dont know if it is the same noise, but in the speakers, you can hear noise that has its peak at 1khz , and goes up with my RPM (2000rpm = 2khz and so on... )
                              In my humble opinion (and I may be wrong) you are tackling the noise problem from the wrong end.
                              While the VGA cable is indeed contributing to the noise with the extra length I assume the noise(hum) is coming from the audio side not the video.
                              If I am right that means you are getting the hum but the video itself is not corrupted.

                              If that is the case, I say leave the VGA cable alone and try to isolate the noise from the audio end by trying to clean up the audio not the video.
                              Ground loop isolators would be a good place to start.
                              I also had a really loud humming noise in my setup originally and to clean things up I first properly grounded the CarPC, then installed ground loop isolators at both ends of the audio path.
                              I made a custom cable by splicing in the GLI (ground loop isolator) where the RCA cables connect to the PC and another where it connects to the head unit.
                              I can remove one or the other of the GLIs without any noise any more but prefer to keep both.
                              This is a bit of overkill if you ask me but I wanted to make sure I am not chasing the problem ever again

                              If however your video itself is affected because the noise is getting into the VGA cable itself then disregard my post.

                              I wish you luck getting to the bottom of your problem as I know how annoying that hum can be.
                              Last edited by Dluvr22; 08-20-2013, 04:00 PM.
                              2002 Chevrolet Avalanche
                              Gigabyte Z97 mITX Intel Mobo, 8GB RAM, Intel Core i5-4590S 3.0GHz Proc, 320 GB Hard Drive, Dual 12' VGA HDMI DVI touchscreen monitors,....
                              http://www.mp3car.com/show-off-your-...avalanche.html

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