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The Kings guide to elimanating stereo noise.

Discussion in 'Car Audio' started by Tasmaniak, Sep 2, 2005.

  1. Tasmaniak

    Tasmaniak Not a valid input....

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    My speakers make this high-pitched whine which matches the engine's RPMs. What is it, and how can I get rid of it?

    This is a set of instructions to debug a stereo installation if there is any noise present after it is completed. Follow each step carefully! If you have more than one amplifier, repeat level one for each amp to be sure that none of them are responsible for the noise.


    Level 1: Check out the Amplifier(s)

    After you have determined that there is noise in the system, determine if the amplifier is causing the noise. To do this, mute the signal at the inputs to the amp by using shorting plugs. If there is no noise, then the amp is fine, and you can proceed to level 2. However, if there is noise, then use a test speaker at the amp's output. If this stops the noise, then the problem is originating in the speaker wiring, or the passive crossovers. Check to make sure that none of these are shorting with the body of the car, and start again at level 1. If noise is still present when using the test speaker, then there may be a
    problem with the power supply on the amp. Try connecting an isolated power supply - if this does not get rid of the noise, then there is something seriously wrong with the amp, and it should be replaced. If the noise goes away, then there may be a problem with power supply filtering or isolation. This can be fixed by changing the amp's earth
    point or b adding external supply filtering.


    Level 2: Reduce the System

    The amps have been determined to be noise free. If you have any processors between the head unit and the amps, disconnect them and connect the head unit directly to the amp. If this gets rid of the noise, then one (or more) of the processors must be at fault, so proceed to level 5. Otherwise, try running the signal cables over a number of different routes. If you are able to find one that does not produce any noise, permanently route the cables in the same manner, and proceed to level 5. If not, then you must isolate the head unit from
    the car's chassis (except for its earth!) - don't forget to disconnect the antenna, since it is also earthed to the car. If isolating the head unit does not solve the problem, the move the earthing point of the head unit. Hopefully the noise will be gone, and you can install the head unit with a quiet earth and proceed to level 5, otherwise go on to level 3.


    Level 3: Move the Head Unit
    ----------------------------------

    The amplifiers are fine, but moving both the earth for the head unit and the signal cables does not solve the noise problem. Take the unit completely out of the dash, and put it on either the seat or carpet, and run new signal cables to the input of the amp. If this solves the problem, re-install the head unit, one step at a time and skip to level 5. But if the noise persists, then move the head unit as close to the amp as possible and use the shortest possible signal cables. This will verify that the original signal cables are not causing the problem - assuming the noise is gone, reinstall the head unit one step at a time and go to level 5. Otherwise, there may be a problem with the power filtering for the head unit. As with the amps, power the head unit with an isolated power supply (again making sure that the head unit isn't touching the car's chassis at all). If the noise goes away, you can add power supply filtering or an isolated power supply; go to
    level 2. But if the isolated power supply does not solve the problem, then you can either replace the head unit and go to level 2, or check the car's electrical system in level 4.

    Level 4: Testing the Car

    There does not seem to be a problem with either the head unit or the amplifier, and the car's charging system is suspect. To see if this is the case, we can use a system in a car that is already known to be "quiet." Bring both cars together as if you were going to jump one, and use jumper cables to connect the two batteries. Start the engine of the car with the noise problem, and listen to the "quiet" car's system. If the noise does not go away, there is a SERIOUS problem with your car's electrical system (possibly a bad alternator). Have a qualified mechanic check the charging system out. If there is no noise in the "quiet" car, then the "noisy" car's charging system is definitely quiet, so continue with level 5.


    Level 5: Adding Signal Processors

    We have proven that the amplifiers are good, the head unit is good, and the car's electrical system is good. Now we need to reconnect each signal processor. Repeat this level for each signal processor used in your system; if you have added all of your signal processors, and there is no longer any noise, CONGRATULATIONS! You've removed the noise from your system! Connect the signal processor. If there isn't any noise, then go on to the next signal processor. Otherwise, try re-routing the signal cables. If this cures the problem, the route them permanently over the quiet path, and install the next processor. If not, then isolate the processor from the car's chassis except for a single earthing point. If this works, then permanently isolate the processor, and move on to the next processor. If isolation does not help, then advance to level 6.


    Level 6: Processor Isolation Tests

    Now, noise enters the system when one particular processor is installed, but reearthing it does not help. Move the processor very close to the amp, and check for noise again. If there isn't any, then re-install the processor, carefully routing the cables to ensure no noise, and continue at level 5 with the next processor. Otherwise, use an isolated power supply to power the processor, making sure that no part of the processor is touching the car's chassis. If this solves the problem, the consider permanently installing an isolated power supply or possibly a 1:1 transformer, and go to level 5 with the next processor. Otherwise, separate the processor and isolated power supply from the car by many feet and re- test. If there is still noise, then there is a serious problem with the processor's design. Get a different processor, and continue at level 5 with it. If separating the power supply and processor from the car does solve the noise problem, then either the processor is damaged, or your tests were inaccurate. Repeat level 5.
     
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  2. RichardW

    RichardW New Member

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    I tried all of these and in most cases they will work, in my case it didnt. So I solved the problem, not the most cost efficent way though. I brought a new head unit, ever since I have had great quality music with no engine, alternator interference. So glad I got rid of the stock HU, the sound quality is a 1000 times better.
     
  3. tropical^fish

    tropical^fish New Member

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    I had bad engine noise with the engine running - so i went out to jaycar and purchased a noise filter... that worked for a while then i started to hear a slight humming noise from the speakers... again.
    The only difference this time was it wasnt matching the engines RPM, and was happening with the engine running also with the engine not running (key switched on accessories).
    This has me confused... any idea what i can do? The HU is relitivly new, and only had this problem since i had a second amp installed - but unhooking the second amp has no effect on the noise, so it has me stumped!
     
  4. Tasmaniak

    Tasmaniak Not a valid input....

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    tropical fish. follow the guide above and you will find out where the problem is.
     
  5. tropical^fish

    tropical^fish New Member

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    i did, but last night i also did a bit of playing and worked out that a fan in one of the amps was making the line noise!
    the amp will be on ebay soon, lol
     
  6. Tasmaniak

    Tasmaniak Not a valid input....

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    well, thats not a nice thing to do. I hope you buy something off of eBay and it's hums and rattles like a MoFo at you to the point that you are disgusted with it and want to rip the arms off of the moron who sold the dodgy item.....oh wait. *******
     
    Last edited by a moderator: Oct 20, 2005
  7. tropical^fish

    tropical^fish New Member

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    its a common problem with the associated model of car amplifier... **************also thats where i originally got it from, and i had the problem since day 1... just never got around to doing anything about it
     
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  8. svs500

    svs500 Guest

    Thanks 12v you're the king. I had noise and it was caused by amp being screwed into metal on the car.I unscrewed it and the noise is gone, but how do i mount it now?
     
  9. Tasmaniak

    Tasmaniak Not a valid input....

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    svs500, thats interesting that you say that, often the case is that by screwing it to the car eliminates noise, not cause it. But hey, if it works!

    Mount your amp to a piece of board and then mount the board to the car....
     
  10. svs500

    svs500 Guest

    Thanks 12Voltking , this is where i read about moving the amp http://www.caraudioaustralia.com/forums/index.php?showtopic=42644 , i had noise when it was mounted behind back seat, car is old, its solid metal, i unscrewed it and sat it on the carpet of the boot (trunk) and the noise is gone.(i'll recheck for noise though now) also my speakers are popping when i turn on/off the car, they are brand new , amp is not, its a 4 channel boss 1200w.
     
  11. tropical^fish

    tropical^fish New Member

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    hey 12 volt - my electric aerial control module seems to be emitting some kind of interference (into the amps) when its up... when you press the down button the noise dissapears, sometimes for a while but usually comes straight back. As soon as i removed the module the noise was gone for good... but then realised that whats the point of an electric aerial if you cant use it, at all!
    any assistance would be appreciated
    thanks
     
  12. Milkman

    Milkman New Member

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    i fixed a m8s car last nite,

    problem: rear(non-amped) 6x9s were popping and sub amp would not turn on.

    system faults: - B+ had slipped off terminal on amp
    - amp was not correcetly grounded

    upon correcting these faults 'popping' noise was eliminated and amp would turn on :D
    -dont ask why :S
     
  13. davey g-force

    davey g-force I'm a sceptic...

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    Awsome instructions 12Volt - well done.

    I'm just not sure what you mean by your comment above???

    Ive just installed new speakers / amp and it all sounded unreal - while the car was stationary!! When I put it all back together and started driving, I noticed that annoying high-pitched whine.

    The amp is under the passenger seat and is earthed to one of the seat mounting bolts. After speaking to Phreddy, he reckons I should've sanded/scraped the black paint off the seat mounting first?? Anyhow, that's the first thing I'll try, but yeah, please explain what you mean above. :thumbsup:
     
  14. Tasmaniak

    Tasmaniak Not a valid input....

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    shorting plugs are simply a little ende cap that go over your RCAs that short them out so there is DEAD silence down the lines. Can be done with anytihng metal.
     
  15. 253@7k

    253@7k 300rwhp supra. yay.

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    So they bridge the + and - of the RCA's?
     
  16. davey g-force

    davey g-force I'm a sceptic...

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    Can I just poke a bit of wire inside the RCA plugs and run it from one RCA plug to the other?

    OR:

    Can't I just unplug the RCA's from the amp, then turn the engine on, stereo on and see if the noise is still there?
     
  17. phree

    phree New Member

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    Seat mounting bolts are notoriously bad earths. Try somewhere else before you do anything else. Make sure it is bare metal and solid.
     
  18. davey g-force

    davey g-force I'm a sceptic...

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    How bout just straight back to the - of the battery if worst comes to worst??
     
  19. phree

    phree New Member

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    The chassis is best. Drill a new hole, clean the paint off the contact area. Use a "star" washer, nut and bolt. Paint over the top after connecting to prevent rust.
     
  20. davey g-force

    davey g-force I'm a sceptic...

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    Thanks phree, good plan.

    Only trouble is, if the problem is still there after I do all that - I don't wanna go drilling heaps of holes in the car just trial & error...
     

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