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Aftermarket Head Unit Wiring Question

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by 93Akkord, Apr 26, 2014.

  1. 93Akkord
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    93Akkord New Member

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    [Apr 26, 2014]
    I'm hoping this will be an easy one for you guys. I've done hours of research up until this point lol.

    Quick Info: I installed a Pioneer AVH-X4600BT with my stock Symphony II (non bose) setup.

    Quick story. I had a shop install my head unit incorrectly. It was producing hiss from the back speakers and a buzz when I turned on my headlights. Well after all the reading I did, I finally got up the courage to hook up the RCA cables so that the hissing will go away. Well I did it, all came out fine. Hissing went away and I found out the shop never grounded period so the hissing went away.

    My question (which may sound dumb to some, but I'm new at this) involves my sub. It is not working now. I am almost positive on what I need to do, but I wanted to make sure as to not mess anything up. This is the back of my head unit.

    head unit.jpg

    ​TLDR

    The top two RCA are for the front two speakers, the middle are for the rear and the bottom are for the subwoofer. Well, I never hooked up the sub RCA's. Would I just connect two more white and red RCA cables and connect them to the corresponding RCA wires prior?

    Edit: Or I do not have it wired correctly for my AMP to come on. Still trying to figure that out.
    Last edited: Apr 26, 2014
    #1
  2. sabaxter
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    sabaxter Active Member

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    [Apr 26, 2014]
    You need to put a set or rca from the ueadunit to the amps location. Then you need to run another cable from the rem input of the amp to the remote wire on the rear of the headunit. Go into your headunit menu and ensure loud is selected. So when you turn your headunit on it will send a signal to the amp to turn it on.

    Hope this helps if not pm me your phone number and I will call you and explain :)
    #2
  3. dualmono21
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    dualmono21 Well-Known Member

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    [Apr 26, 2014]
    loud setting has nothing whatsoever to do with remote signal or subwoofer
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  4. dualmono21
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    dualmono21 Well-Known Member

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    [Apr 26, 2014]
    are you using the standard non bose amplifier for the sub-woofer ?
    or are you adding a separate amplifier to power the sub-woofer ?
    #4
  5. sabaxter
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    sabaxter Active Member

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    [Apr 26, 2014]
    My after market headunit requires loud to be selected to enable my subwoofers.
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  6. 93Akkord
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    93Akkord New Member

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    [Apr 26, 2014]
    Sorry, long night lol. I'm using the standard Symphony (NON-Bose) speakers and amp with my head unit.
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  7. dualmono21
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    dualmono21 Well-Known Member

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    [Apr 26, 2014]
    the loudness button is designed to compensate for high and low frequency at low levels
    your ears hear frequencies different at higher levels
    aka.. fletcher munson curve

    if your using the standard amplifier you may as well the standard wiring ... no need to run a seperate rca cable
    just buy the correct lead to match your new after market headunit to your old non bose system
    #7
  8. easy going Si
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    easy going Si Member

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    [Apr 27, 2014]
    I presume there was an amp in the back ??? look in the boot on the left hand side your amp should be there (behind the trim panel) if one was fitted if you can get to the amp you can easily find the pin in/out connection diagram via google you may have to take the amp out but with this you can type audi part number in to the search bar and you will see lots of pics

    Grounding the unit back to the battery is most important (clean earth) where your battery is on the right hand side just behind it is a grommet (it means taken the glove box out) but you will be able to wire the stereo direct from the battery I took the grommet out and was able to feed 4x 41 amps red and 2x 17 amps red and 2 x 37 amps black cable and then wrapped 12mm spiral wrap around the cables the grommet needs to have the all the centre cut out if you don't need all that cable just cut a hole in the grommet as required

    Also I would strongly suggest you get an alternator suppressor Audi,s are prone to noise see if you have a durite dealer near you they do a 4.7 microfared suppressor ( £7 ) that bolts onto to the alternator and makes a world of difference (metal tab bolt's to earth case of the alternator, lose blue lead goes to the positive output of the alternator (red m8 crimp eyelet) m8 nut with a plastic cover over it you know this wire as it goes to the main cable on your starter
    #8
  9. lilnizzel
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    lilnizzel New Member

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    [May 1, 2014]
    you know you said audis are prone to noise, as in it affects the sound of the stereo or noise in general from the engine bay?
    #9
  10. dualmono21
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    dualmono21 Well-Known Member

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    [May 1, 2014]
    cars in general have a noisy electrical environment
    simply because most manufacturers choose to use multiple earth's as opposed to a star ground with one single ground differential

    install the stereo correctly with a proper star ground and you do not need any suppression
    #10
  11. easy going Si
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    easy going Si Member

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    [May 6, 2014]
    Hi yer Lilnizzel

    Daulmono21 is correct cars have very noisy electrics remember how many wires are in a car and all the electrical components they can all induce or create noise, when you send electrons down a conductor (Wire or Cable) you produce an electro magnetic field and this creates noise which travels down the to the power cables which give your amp power it's how you deal with this that's important I.e. when your alternator is brand new it has a suppressor fitted but this is like any electrical component which has a finate life span it wear's out

    As an alternator produces current (electricity ) it produces AC but what a car wants is DC so it has a set of rectifying diodes which are fitted they chop the alternating waveform so you get a very smooth dc current but you always get a small ripple of Ac current in with the dc its this that give's you alternator whine it may not be the suppressor but the alternator that could be at fault i.e. the diode pack or the alternator itself, that's where an alternator suppressor comes in it chops the AC ripple out of the alternator's output

    I cannot agree with Dualmono more in car stereo filters and suppressors only chop out the frequencies that are the problem they are more of a sticky plaster than a cure it is far better to plan your install properly and if you do end up with noise as I did, you have find out the noise your getting and work back from there I recently worked on an install and found ferrite beads did the trick they don't stop a cable from picking up noise but stop it irradiating noise so other wires in the loom are less likely to pick this noise up it was also the first time I've used 2 x 2 core 4mm copper shielded CWA cable as speaker wire but this helps to shield the speaker cable

    plan your install properly
    #11
  12. lilnizzel
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    lilnizzel New Member

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    [May 6, 2014]
    Had to eras that 5 times to understand it, think I may have some more work to do to reduce the noise, I also have a new alternator fitted to. Thank you for the great advice guys!
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  13. dualmono21
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    dualmono21 Well-Known Member

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    [May 6, 2014]
    if you read what i actually said it doesnt mention anywhere about using more filters or suppressors
    what i suggest is getting the correct grounding (star grounding or single point grounding)
    people who are very serious about car audio found out a long time ago that having one single grounding point for the system is the best way to eliminate noise from the entire system ... not filters suppressors and other ********
    #13
  14. PetrolDave
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    PetrolDave Well-Known Member

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    [May 6, 2014]
    +1

    A couple of years ago I was working at a company that installed very sensitive radio equipment into cars, we would often find up to 3 VOLTS difference between the chassis at the front of the car and the rear when cranking if the battery was rear mounted - car bodywork is high resistance so it's really bad for an electrical connection.
    #14

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