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Mic Pre-Amp Chips?

Discussion in 'Electronic Basics' started by LightBoy, May 9, 2005.

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  1. LightBoy

    LightBoy Guest

    Hello all,

    Does anyone know if anyone makes a "chip" to do microphone
    pre-amplification? I know cobbling such a circuit together with a
    couple of transitors resistors and capacitors is fairly easy to do -
    but I'm wondering if a chip exists that would be quicker - easier and
    better. If such a thing exists - what would be a part number for it so
    I could research it?
    Thanks for any an all help!

    Don H.
     
  2. Michael

    Michael Guest

    There are tons of chips that do what you need. Really any audio
    amplifier would work, TI has several in both analog (class AB) and
    digital (class D) varieties. Search through the audio section of
    TI.com and see if can find one that meets your needs (supply voltage,
    output power, load impedance etc.). They also do free samples of
    certain products.

    Another option is to use a simple op-amp circuit. A couple of
    resistors to control the gain and your done (unless you want to get
    fancy).
    happy hunting!

    Michael
     
  3. LightBoy

    LightBoy Guest

    Michael !

    That is such a great idea! The op-amp route I mean. I will look into
    that for sure. I will also check out your suggestion of looking to see
    what TI might have.
    Thanks so much for your very helpful reply.
    Many Blessings!
    Don H
     
  4. Ban

    Ban Guest

    If you want a professional quality pre one chip solution try this
    http://focus.ti.com/docs/prod/folders/print/ina217.html
    this is meant for balanced operation. But if you just have a small electret
    mike capsule, an inverting opamp stage will do as well.
     
  5. LightBoy

    LightBoy Guest

    Thank You, Ban,

    I looked at the link and at the product in your posting. It would be
    perfect - as would other op-amp soulutions, except for the fact I would
    have to completely re-do the power supply to provide + (plus) and -
    (minus) voltages.

    As this is for installing in an existing product - I really hope to
    find a solution that does not require a plus and minus voltage supply.
    I will keep looking and very much appreciate the suggestions I am
    receiving here. I am sure I will find some solution - probably through
    all the great people in this group.

    My best to you!

    Don H
     
  6. Ban

    Ban Guest

    Don, maybe you should scan the circuit or at least specify what voltage you
    have available and what kind of microphone you want to connect.
    Some mikes require a small DC-voltage (electret-capsules) to function,
    others (professional condensor-mikes) need phantom-power (12 to 48V), some
    have built-in batteries and some (dynamic) do not need any DC supply to
    function properly.
    Also the above chip doesn't necessarily need a bipolar supply, it also works
    as well on a unipolar supply between +8 and +36V. There are ways to create a
    virtual midpoint when you couple the signal via capacitors.
     
  7. LightBoy

    LightBoy Guest

    Ben,
    Now you have asked, I will explain a little further.
    I don't require a high quality as I will be using the sound output to
    modify the intensity of a string of LED's only. I have available 12 and
    5 volts DC - filtered. I will be using a cheap 3 wire "Radio Shack"
    minature mike - placed within 6 inches of the amplification stages. I
    have used a one transitor pre-amp - driving an LM386 amp module. This
    works - but I need a little more sensitivity.
    You are most kind to be of such help. A professional circuit designer I
    am not - but have managed to put together lots of things that work
    well.
    The idea behind what I am doing is to get the string of LED's to
    respond to voice and music input - much like the "color organs" so
    popular in the early 70's.
    I hope this all is a little more helpful by way of an explanation.
    Blessings to you in beautiful Italy!
    Don H
     
  8. Paul Jones

    Paul Jones Guest

    I'm in Thailand .... Just bought 120 mikes for $6
    They are cap type w/ built in FET amp
    But i'd still need a current amp for long distance
    There's plenty of voltage so just do a curr amp
    It makes the mike look like it's a 1 ohm mike
     
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