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High pitched noise from rear speakers

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by Jay4, Aug 28, 2007.

  1. Jay4
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    Jay4 Member

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    [Aug 28, 2007]
    i've recently swapped the Concert 2 headunit in the car for another (non audi) headunit and am getting a high pitched noise from the rear speakers when the headunit is switched on. The noise is constant so is not too bad at high volume but if the headunit is fairly low on volume, the high pitched noise can be heared through. Any ideas what this could be?
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  3. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Aug 28, 2007]
    Is it alternator whine (does it go up & down with the revs) or something else?
    If it is then try earthing the chassis of the HU to the cars chassis behind the glovebox. Also what adapter are you using to connect the new HU to the rear amp?
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  4. Jay4
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    Jay4 Member

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    [Aug 29, 2007]
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  5. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Aug 29, 2007]
    that's the speaker input adapter which could be the issue. Essentially it's taking the amplified speaker signal from the new HU and reducing it down to a pre-out signal, only to be re-amplified again by the Audi rear amp. This is prone to creating electrical noise as the hi-lo converter is bound to be poor quality.
    Maybe worth trying the RCA input adapter (as long as the new HU has rear RCA's) as this is a far cleaner solution.
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  6. jase0851
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    jase0851 Member

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    [Aug 29, 2007]
    i just ran new wires from the headunit to the connector block in the rear which was pluged into the amp, under andys advice, and the rears work a treat now much better than before. need to wire up the head unit properly next
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