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Amplified speakers have engine noise?

Discussion in 'A3/S3 Forum (8L Chassis)' started by russwuss, Feb 22, 2014.

  1. russwuss

    russwuss Active Member

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    Hi All,

    Well today has been a waste of time!

    Driving along one day and the rear amplified speakers started squealing, the higher I revved the higher the pitch... At this point I just thought the standard amp was knackered.

    Ripped out the standard unit today, brought a decent 4 channel amp - wired all up and the engine noise is still there!

    Tried it with the front speakers also, exactly the same noise.

    The ground for the amp is the ground behind the standard sub, also tried it on the sub but same thing happened..

    Anyone have any ideas? Started this at 11 and just finished / gave up.

    Thanks in advance!
     
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  3. Rrobson

    Rrobson Member

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    I was always under the impression that this was to do with running the power cable alongside the amp cables.

    Electricity creates a magnetic field as if flows through a cable (or any object in fact) so if the power cable is close to the speaker cables the magnetic field can disturb the audio signal. The frequency of the disruption is subjective of the engine revolutions (obviously as faster revs means the alternators spinning faster and created the frequency)

    Best thing to do is either run the speaker cable a little further away from the audio cable , or better still run them on either side of the car. That should sort things out
     
  4. russwuss

    russwuss Active Member

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    Unfortunately I'd tried that one.. Ran the wires straight from the stereo to the back between the seats to test and although it was better, the noise was still there...

    I accidentally forgot to put the alternator lead on the battery and that stopped the whining but noise was still there..

    A 3 year old American Kid on YouTube suggested to put speaker wire inside the RCA adapters? I would have thought that would introduce more noise....


    Thanks for the suggestions!
     
  5. lol4fun

    lol4fun Member

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    You have dodgy earth somewhere, maybe on the CD player or maybe on the amp.
     
  6. russwuss

    russwuss Active Member

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    The CD player is probably the only earth I haven't checked haha, checked all earthing points under bonnet (I think) and the one behind the sub.. They were a little rusty so cleaned up and noise was still there :( you happen to know where the CD player earth is? My guess is under the dash?
     
  7. lol4fun

    lol4fun Member

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    Try as a temporary fix running battery ground to the chassis of the CD player. Also there will be a ground going alongside the left and right lines to the amp which will be worth checking
     
  8. russwuss

    russwuss Active Member

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    Ahhh okay will give that a go tomorrow.. It must just be a loose cable or something - just started as I was driving, thought it was my fuel pump knackered at first haha.
     
  9. lol4fun

    lol4fun Member

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    Alternator noise is definitely a ground issue somewhere, another possible is engine to chassis ground and battery to chassis ground, make sure they are solid and not corroded
     
  10. russwuss

    russwuss Active Member

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    Battery to chassis ground I have checked, the battery wire itself has lost it's plastic coating in places, ground point was rusty - cleaned it up and still there.. Going to have a look on Elsawin to see if it point out where the engine to chassis ground is.. Thanks!
     
  11. Gops

    Gops 6th gear @7000rpm
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    What adaptor did you use? I remember AndyMac suggesting it was one of the PC adaptors..
     
  12. Stevieb2905

    Stevieb2905 Active Member

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    Had same issue years ago, cant even remember what car it was, but cured it with a gizmo called an 'in line choke'. Just a small hard plastic tube, think it contains magnets, which clips over the power supply (and possibly earth) connections to the head unit and amp. I think it dissipates or prevents the build up of magnetic fields. I used quite a few, they are not expensive. If all else fails may be worth a try.
     
  13. russwuss

    russwuss Active Member

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    I was using one of his hi-lo convertors to make the rear speakers work.. but now it's wired with new RCAs, new power & remote cable to the new amp and still doesn't work :-(

    The only thing that's common between the new amp and the old audi unit is the pioneer head unit..
     
  14. russwuss

    russwuss Active Member

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    Ahhh I will get one and find out, hopefully this does sort it once and for all - thanks a lot!
     
  15. Gops

    Gops 6th gear @7000rpm
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    I see.. I Rembrr Andy saying something sbout having a pc9-404 in a thread somewhere..
     
  16. russwuss

    russwuss Active Member

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    Do you have a link to one of the ones you've brought?

    I seen this one https://www.bluearan.co.uk/index.php?id=EVNB070C&browsemode=manufacturer# which sounds like it would do the job, just worried my amplifier will run higher amps than 20A and blow it - if i'm honest I'm a complete electronics novice.
     
  17. russwuss

    russwuss Active Member

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    Oh sorry.. I thought I brought the lead off Andy, yeah I did have one on those installed - not anymore though, wired the rear speakers directly to the aftermarket HU. To say the speakers are standard they are not that bad, focal comps in the front make up for it :)
     
  18. bi_a_op

    bi_a_op New Member

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    You have ground loops. Google it for explanations but basicly just try other ground points. If you have multiple amps make sure they all use the same ground nut. Try grounding directly to - terminal
     
  19. russwuss

    russwuss Active Member

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    I've tried going to a different grounding point also.. the noise was still present. I'm starting to think it's not the amplifier at all.. it's something to do with the head unit - apparently the older Pioneer head units (I have a Avic F900BT) are known for not having the best internal grounding - I think the RCAs are picking up on that as the noise disappears as soon as the RCAs are unplugged, so the head unit must be putting out that noise. Going to order one of those in-line chokes to see if that fixes the issue, if it doesn't I'm stealing the brothers head unit and see if that works :)
     
  20. bi_a_op

    bi_a_op New Member

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    Yeah, try a different head unit. You could also try grounding RCAs but I read somewhere that it's not recommended, can't remember exactly why.
    Prelude158.jpg
     
  21. russwuss

    russwuss Active Member

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    I saw another head unit with wiring like that and never knew what it was for! I'll do the power line filter and if that doesn't work i'll try grounding the RCA - thanks - 10 hours spent on this issue!
     
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  23. russwuss

    russwuss Active Member

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    well... noise was still there after fitting a ground loop isolator, was better but no perfect - think it's killed 2 focal tweeters in the process..

    turns out it's my head unit at fault, pioneer units are known for blowing an internal 'pico' fuse when an issue is detected with an RCA.. all that time spent looking for issues with the car and it's the unit all along - POS!!
     
  24. bi_a_op

    bi_a_op New Member

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    Yeah thats right. I remember that when researching my own problem. Blown tweeters usually doesnt play a single sound when blown or just sissly noise. Like my 210 gbp pair :(
     

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