audio input for VU meter

Discussion in 'Wireless & RF Design' started by shinigami.alv, Apr 24, 2012.

  1. shinigami.alv

    Thread Starter New Member

    Feb 23, 2011
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    [​IMG]


    I have a VU meter circuit as above with a condenser mic which i bought online http://www.cytron.com.my/viewProduct...ondenser Mic and is wondering how can i apply the output of the mic to the audio input of LM324? do i simply amplify the mic output then connect to the circuit? and will 9V suffice for this circuit?
     
  2. TecknoTone

    New Member

    May 20, 2012
    21
    1
    There is no single input to the LM324. This chip is an op-amp array with four amps per chip. Your diagram shows eight amps and therefore two LM324 chips. The 1K resistors act as a voltage divider giving an incremental reference to each amp. If the audio level exceeds the reference level on a given amp, the LED will light.

    Yes, you will need to amplify the signal from a mic in order to drive this circuit. Mics only produce microvolts and you'll need a few millivolts at least to drive his circuit. Half wave rectification and a little bit of capacitance for smoothing an DC blocking wouldn't go amiss either

    This circuit is odd as everything is referenced with respect to +V rather than 0V
     
  3. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
    363
    It's strange to call it a VU meter when the resistor ladder steps are all equal value instead of semilogarithmically stepped like a VU meter.

    http://www.ti.com/litv/pdf/snvs762a
     
  4. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    2,039
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    Alas....in recent years, many folks consider ANY kind of audio meter a VU meter. A true Bell Standard VU meter has precise logarithmic level calibration as you mention AND very specific ballistics!

    This takes some care and expense to achieve....unfortunately it has fallen victim to language inflation. :)

    Eric
     
  5. TecknoTone

    New Member

    May 20, 2012
    21
    1
    What are you trying to achieve Shinigami ? Perhaps if you can set out your aims, we will be able to help you more
     
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