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sorry! ISO harness question!

Discussion in 'In-Car Entertainment' started by stapo69, Mar 29, 2007.

  1. stapo69
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    stapo69 All hail the mighty quattro!

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    [Mar 29, 2007]
    Right, I've looked and looked through this forum and I've ended up getting more confused about which lead i need for my car to connect my kenwood head unit

    I have a 1999 S4, full amped Bose. Which ISO connector do I need? The one to connect my head unit RCA's to the existing BOSE set up?

    Please help, once and for all! Even ICE specailists have given me different answers!

    PC9-401? PC9-404? PC9-408? PC9-410? AAAAHhhhhhhhh
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  3. Randomjim
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    Randomjim Active Member

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    [Mar 29, 2007]
    PC9-408 i believe
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  4. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Mar 29, 2007]
    the 408 will connect to your speaker outputs and use a hi-lo converter to take the amped signal back down to RCA/pre-out level, which then gets re-amplified by the Bose amp.
    The 410 is just a straight adapter that takes the front & rear RCA's directly into the Audi loom to feed the Bose amp.
    You can use either, but the 408 will compromise the sound quality as it's being amplified twice, so more distortion and background noise.
    The 410 is theoretically the best one, but can produce really annoying popping noises when changing CD track. This depends on the HU and the RCA pre-out/RCA voltage.
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  5. mordz
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    mordz Audi S3 (2000)

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    [Mar 30, 2007]
    i have both 408 and 410, the 410 is better if you have an amp with 2 RCA channels - as Andymac says, quallity is lower on the 408 (and quite noticable)

    im just using a sony HU and not had a any 'pops' yet.
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  6. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Mar 30, 2007]
    The pop issue does seem to be totally inconsistent, some people get it some don't. If you don't get it then you won't get it.
    It seems to be more apparent on HU's that have a high pre-out voltage. Some of the tech info does state you should use the 408 if your RCA level is 4v or higher. It's to do with discharging capacitors on the input stage to the Bose/audi amps, and can only be eliminated by fitting capacitors to the RCA line - there was a write up on here about how to do this.
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  7. stapo69
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    stapo69 All hail the mighty quattro!

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    [Mar 30, 2007]
    Lovely, cheers guys.
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  8. mordz
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    mordz Audi S3 (2000)

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    [Mar 31, 2007]
    btw If ya HU has only 1 RCA out you can use a Y splitter to hook up the other 2 RCA ins on the harness. Maplins sell some for £3-4
    #7

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