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Headunit wiring help please !

Discussion in 'A3/S3 Forum (8L Chassis)' started by Sam-K, Jul 5, 2007.

  1. Sam-K
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    Sam-K Has a throbbing red german.

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    [Jul 5, 2007]
    i have done a search ,

    but can't find what i'm after.. basically.

    i have a 97 1.6 sport a3, and have changed the headunit to an alpine one , but the way i have wired it without the correct harness leaves the rear speakers not working, so i would like to know what harness i need for my car , it's not a bose system or anything, but has one of those funny little subs hidden in the rear passenger side bit :)

    help would be well appreiciated!!
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  3. steve1975l
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    steve1975l Member

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    [Jul 5, 2007]
    Connector I pins 1-6 connected OK I assume.
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  4. Sam-K
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    Sam-K Has a throbbing red german.

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    [Jul 5, 2007]
    my connector (alpine end) only has four pins.. so i need to know what harness i need really.. :(
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  5. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Jul 5, 2007]
    There are 2 adapters, one uses the RCA's of the Alpine to feed the rear/sub amp, the other uses the rear speaker output of the Alpine via a hi-lo converter.
    The RCA adapter is technically the best one to use, but some HU's cause the rear amp to "pop" when changing CD tracks, which is a "feature" of the stupid Audi amp design. Autoleads Part No. PC9-404
    The speaker input adapter won't induce any popping but is technically less clean as the signal is amplified at the HU then reduced back down to pre-out level by the adapter then re-amplified by the Audi amp. Autoleads Part No. PC9-401
    The popping issue seems to depend on the pre-out voltage of the HU, s if it's a 4v+ then I'd recommend using the speaker input adapter.
    The best solution is to actually rewire the rear spekers directly to the HU and cut out the 2 x 20w rear amp as it'll be completely ovepowered by the Alpine front amp driving the fronts. You can then use the RCA adapter connected to the sub out of the HU Iif it has one) to just drive the tupperware sub and also give you some control of the sub independent of the rears.

    You can get the adapters from big Halfords or online:
    http://www.bluespot.co.uk/install/show_model.asp?id=15
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