Line out from an mp3

Discussion in 'General Electronics Chat' started by amjg92, Apr 12, 2011.

  1. amjg92

    Thread Starter New Member

    Dec 14, 2010
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    Hi I need to know what is the maximum peak voltage that can be measure from and mp3 playing some music at full volume. If no one knows a numerical value guide me to how to find it. thanks
     
  2. matty204359

    Member

    Apr 6, 2011
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    use digital multimeter? probably want to do it with your load attached whether is external amplifier or headphones... but why on earth would you need that information? I suspect the voltage would be different depending on the make and model of the MP3 player and the load because different speakers have different impedance.
     
  3. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    it would be around 400mV to 775mV. The standard value is the latter. ( Voltage is RMS value)
     
  4. matty204359

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    Apr 6, 2011
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    Wouldn't the peak be higher than RMS? isn't the RMS the average?
     
  5. bertus

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    Apr 5, 2008
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  6. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    RMS is not the average.

    RMS is the 70.7% of the Peak Value.
    Average is 63.6% of the Peak Value.

    Now u do the math.

    In some low grade players, out put is lower.
    By standard I meant in Good quality brands like, Sony, kenwood and the likes.

    These guys had a standard out of 775mV level. If other that, it will be stated in the manual. Some DJ mixers and and pre-drives have a higher output up to 1V
     
  7. Audioguru

    New Member

    Dec 20, 2007
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    A multimeter accurately measures the 50Hz or 60Hz mains voltage, not other audio frequencies.

    The peak and RMS voltage of every recording is different. That is one reason why radio stations have audio compressor/limiters.
     
  8. nigelwright7557

    Senior Member

    May 10, 2008
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    My mp3 player wont drive my amp to full power on line in so the output must be considerably lower than 0db.
     
  9. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    To drive high power amp u will atleast need approx 1.0V without distortion
     
  10. amjg92

    Thread Starter New Member

    Dec 14, 2010
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    Thanks Everyone it was very helpful. I need to know the value because I am designing an audio amplifier and i have to take in consideration the input voltage. thanks again
     
  11. Audioguru

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    Dec 20, 2007
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    Most audio power amps have more than enough gain so that the volume control can turn down or turn up the loudness.
     
  12. W123

    New Member

    Apr 27, 2011
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    What kind of amp? If youre looking to design a headphone amp, use the Chu Moy as a layout. Im listening through an 18v version right now. Thats a heck of a solid layout and it fits perfectly in an Altoids tin.
     
  13. Audioguru

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    Dec 20, 2007
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    A Cmoy opamps headphones amp can drive expensive 600 ohms very, very, very, very expensive headphones perfectly. It drives ordinary cheap 32 ohms headphones poorly.
    You need a power amplifier to drive 32 ohms cheap headphones.

    Don't you trhink that very, very, very, very expensive 600 ohms headphones sound better than cheap 32 ohms ones??
     
  14. W123

    New Member

    Apr 27, 2011
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    Exactly. Im listening to AKG K240 Sextetts now through one. Amazing sound. Great design.
     
  15. Audioguru

    New Member

    Dec 20, 2007
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    Yes, high quality (expensive) headphones sound a lot better than cheap ones.
     
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