[solved] Electronics gurus : i'm stumped on this one :(

Discussion in 'Electronics & Electrics' started by cyrax83, Sep 12, 2006.

  1. cyrax83

    cyrax83 Member

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    Ok this may seem like a caraudio question but its more about current and impedence. I've got an amp with rca input, i want to however run both my carpc and my headunit. I tried a AV switch but i got alot of noise and background junk when both where connected.

    So i'm considering just using a "Y" splitter on the rca in and just plugging in both inputs directly into it.

    I found this on another forum :

    Is what this guy saying is true ? i.e. it shouldnt damage any of my equipment doing this ? What i'm worried about is say I turn my headunit to mute, since its not outputing a signal, will the carpc's signal travel up to the headunit and damage it ? or vice versa ? :confused:
     
    Last edited: Sep 13, 2006
  2. dakiller

    dakiller (Oscillating & Impeding)

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    It won't damage anything as such but it wont work very well at all either, most attempts I've had with mixing signals like you mention have resulted in very screwed up sound

    The easiest way would be to have a switch to switch between each input, you don't need to have both going at the same time? That will greatly simplify it
     
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    cyrax83

    cyrax83 Member

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    I wont have both going at the same time, so yes a switch is the logical thing, and i did try it first, but it didnt work.

    I tried a simple jaycar $20 AV switch. Easy enough to use, 2xrca in, 1xrca out. Connected it up. Heres the problem, when I have both inputs connected to the switch, I get loud background noise on both inputs.

    The noise isnt as bad when switched to input A but is very loud on input B. It doesnt matter which way i have the inputs going into the switch, its always this way. When i disconnect one of the inputs (either one), the noise goes away.

    I thought it might be the unit so i went to dick smith and asked if i could just try out there $40 switch. Put it in, exact same problem, except the noise wasnt as bad but it was still there.

    So i ditched the switch idea, the Y splitter is the only thing left :(

    Will it decrease sound quality ?
     
  4. dakiller

    dakiller (Oscillating & Impeding)

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    Sounds like a ground loop, you want a switch that will switch the ground connection on each as well, something like this will switch all the signals at the same time, I don't know what the AV switcher looks like but you should be able to mod this into it to switch the ground wires as well
     
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    cyrax83

    cyrax83 Member

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    the strange thing is that the carpc and the headunit are grounded at exactly the same point (stock wiring harness).

    anyway, the av switch has a big rocker switch at the top that you can 'rock' from input 1 or input 2.

    on the back of the unit is two sets of input and 1 set of output. if pictures will help let me know.

    How would i go about modding that switch into the unit ? Not sure how you would do it with rca cables. Do rca switches exist that actually switch the ground wire as well or something ?

    what about an inline ground loop isolator (ebay ones)
     
    Last edited: Sep 13, 2006
  6. LethalCorpse

    LethalCorpse Member

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    You can use a ground loop isolator to solve the noise issues where your switch is concerned. Do not attempt to mix the two signals witha Y-splitter. I think you already spotted the potential problem - If you mute one signal, it's outputs are grounded, and hence you're shorting the other signal directly to ground. It's just not a good idea.

    The only other option is a proper mixer.
     
  7. 2xCPU

    2xCPU Member

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    I'll go with the ground loop theory.

    To test the theory, unplug one pair of RCAs to the point that only the center pin is in contact. Use which ever cable has the longer pins

    Test both inputs and see how you go.

    if this works, pull the switch apart and cut the grounds to one pair of inputs.

    2
     
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    cyrax83

    cyrax83 Member

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    I tried that actually

    I had input A fully in and input B only half way in (center pin).

    This resulted in input A being 100% working no noise, and input B had alot of noise.

    If i have both plugged in, input A has a bit of noise and input B has alot, so yeah, not 100% its ground loop

    any other suggestions ? Would something like this work for an isolator : http://cgi.ebay.com.au/BEST-WORKING...ameZWDVWQQrdZ1QQcmdZViewItem#ebayphotohosting
    Bit dodgy on $10 shipping but i cant seem to find any shops like dse, jaycar etc selling the isolator
     
    Last edited: Sep 13, 2006
  9. 2xCPU

    2xCPU Member

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    The isolator might work, but you might need two of them!

    Strathfield, Gary's or JB might carry them.

    Try repeating the test above with all (4) inputs only making center pin contact.

    2
     
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    cyrax83

    cyrax83 Member

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    you guyz are champions :D

    went to strathfield and bought a ground loop isolator ~ $20, put it on the headunit line, all noise went away immediately :thumbup:

    thanks everyone for your help.

    quick question : someone explain to me what a ground loop is in lamens terms ?
     
  11. Goth

    Goth Grumpy Member

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  12. andrew_bg

    andrew_bg Member

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    I came in too late to offer assistance, but I had the exact same setup as you.

    Car head unit -> Amp
    carputer -> Amp

    on Y adapters.

    And yes I had ground loop issues and experienced the exact same issue that you describe.

    I needed two of the isolators to fix my issue, but once I did that everything was absolutely perfect.

    AD
     

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