Electrical Noise Getting Into Audio Amplifier In A Bus

Discussion in 'Embedded Systems and Microcontrollers' started by Abdul Razzaq, Oct 29, 2015.

  1. Abdul Razzaq

    Thread Starter New Member

    Oct 29, 2015
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    how to reduce noises of engine from bus amplifier system?
     
  2. Abdul Razzaq

    Thread Starter New Member

    Oct 29, 2015
    6
    0
    Hi all,
    I am designing an amplifier system for a bus which is serving all passengers like DAEWOO BUS
    at a time. this system is working good in normal case. but when driver accelerates, the sound
    of engine is mixed up with audio signal and causes a noise. I don't know how to remove this
    noises from my amplifier system. One thing to know that a common amplifier TV, and mp3 player
    is used to amplify audio signals and next individual passenger will be served his
    headphone/ handsfree as individual headphone jack adjacent to his seat. Also all headphone
    with all seats are connected in parallel.
    I will be thankful if someone help me out in this problem.
     
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Single-point-ground for the entire audio sub-system, including the microphone, the amplifier, the speakers, and if you are using a radio, mp3, or CD player for a music source, it must be tranformer-coupled.

    There can be only exactly one connection to the bus chassis ("ground")!
     
  4. ian field

    Distinguished Member

    Oct 27, 2012
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    Is the bus petrol or diesel?

    If its diesel, the noise is probably alternator whine - usually easier to fix than ignition noise on a petrol engine.
     
  5. Abdul Razzaq

    Thread Starter New Member

    Oct 29, 2015
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    thanx for reply!
    the bus has diesel fuel.
    by grounding with chassis, not a good noise reduction.
    should I use any filter design to remove engine noise from the audio? then how can I do?
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
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    Should be possible to buy a suppressor kit for the alternator.

    Try that first - ask again if problem isn't cured.
     
  7. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    I get paid for fixing alternator whine in aircraft audio systems. I have been doing it for twenty plus years. The problem stems from common-mode alternator currents flowing along the bus chassis and body. No amount of filtering will cure it if the ground-loops are not broken up.

    Filters that are mounted on the alternator are there to suppress RFI (brush hash at AM broadcast frequencies) and will do nothing for your audible Alternator whine issue. They are for preventing the alternator brushes from interfering with AM radio reception.

    LC Filters on the DC power going into the audio amp may create a slight improvement, but there is a very low probability that will solve your issue.

    Un-grounding parts of the audio system, especially the things like mic jacks, headphone jacks, speakers, that are the furthest from where the audio amp is mounted will do more to get rid of the alternator whine than any other single thing.

    Imagine building the wiring harnesses on a wooden table top (where there is no such thing as a "local ground"), and yet making the system work for testing.

    You would have to run explict ground wires (shields) for every branched circuit, from every remote part of the audio system back to the audio amp. Imagine that the ground wires (shields) are insulated (jacketed) such that they cannot touch the bus metal. All of the shields should be tied to the audio amp's common point (ground mecca). None of the shields are Ohmically connected to the bus chassis. Every remote jack has to the kind that is electrically isolated from the bus metal at the point where it is installed (it cannot connect to "local ground)".

    When you install the system in the bus, there will be only one wire going to the bus body (0V, for powering the amp). No other part of audio system can be grounded anywhere else but this one point.

    This method works. It is a lot of work to do it right. I have pulled miles of wire out of aircraft, and replaced the old wiring and components with new wiring that obeys the "single point ground" principle.

    If you do not do this, you will always have varying degrees of alternator whine in your audio...
     
    Last edited: Oct 30, 2015
  8. Abdul Razzaq

    Thread Starter New Member

    Oct 29, 2015
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    hi, thanx MIkeML for your valuable opinion.
    Already we have done common grounded with bus body using a choke filter which is used in Tube Lights. it works well but not satisfactory. it recomended by a professional working in electronic market.
    I want to get ride off from this choke like solutions. I want to solve this problem using an efficient amplifier r filtering design. If, in your opinion, it is possible and affordable by involving a small circuitry then I should do this, otherwise go on an old solution.
    Also I m not willing to use suppressor kit etc............!
     
  9. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    Try reading post#7 again.
     
  10. Abdul Razzaq

    Thread Starter New Member

    Oct 29, 2015
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    ok thanx got it.... thank u very much
     
  11. Abdul Razzaq

    Thread Starter New Member

    Oct 29, 2015
    6
    0
    I m using TDA2822 amplifier for individual box with every seat to amplify weak audio signal coming from a mp3, tv etc. here this is working good practically. Now I want to add base on this individual amplifier. how can I do? Any solution for this?
     
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