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microphone preamp

Discussion in 'Electronic Design' started by [email protected], Jan 15, 2007.

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  1. Guest

    I need to record sound coming from a large space (a room) with a
    microphone connected to a PC soundcard. So far the results have been
    disappointing, and I've been suggested that I need to preamp the
    Can you kindly suggest a <VERY SIMPLE> circuit design (I'm a begginer)?
    I don't need anything complicated, since I can sustain without problem
    reasonable amounts of noise and distortion.


    Alessandro Magni
  2. Eeyore

    Eeyore Guest

    At what volume level roughly ? Similar to ordinary speech for example or much
    quieter ?

    What kind of microphone ?

    The cheap type that plugs into your PC soundcard or a 'decent' low impedance
    balanced one ?

  3. Guest

    i don't know from which place ur from, if ur in Bangalore, visit to SP
    road were u find all types of electronics gadgets, if ur in any other
    places visit to ur near places were all types of electronics goods are
    sold and serviced,
    when u go there ask for VEGA KITS booklets, in which u find all type of
    electronics project for beginner and expert using this project u will
    improve ur skill in electronics

    there many types of microphone preamp,
    1. type of microphone,
    2. type of enviroment
    3. economy circuit
    all this is available in VEGA KITS try this out or log on to
    WWW.VEGAKITS.COM, and build ur own circuits

    take care when assembling components
  4. What is the problem:

    (1) Is the recorded sound too weak?

    (2) Is there too much background noise in the recording?

    (3) Is there too much echo in the recording?

    (4) Is there too much bass or too much treble?

    (5) All the voices sound like xylon robots?

    (6) One or more of the above?
  5. Guest

    the cheap one!

    Ancient_Hacker ha scritto:
    the problem is (1): recorded sound almost inaudible [on the software
    side the rec levels seem to be allo OK]
  6. Eeyore

    Eeyore Guest

    OK. Electret presumably ?

    I don't quite follow.

    When recording do you have a decent recording level on whatever meteting your sound application
    provides ?

    When playing back, is the wanted sound inaudible in a sea of hiss ?

  7. Phil Allison

    Phil Allison Guest

    ** See:

    Provided you have a decent balanced dynamic mic and not a POS electret

    ........ Phil
  8. John B

    John B Guest

    A PC sound card is designed to work with an electret mic. You are
    probably using a dynamic mic.

    Try typing "microphone amplifier" into Google, It's amazing what turns
  9. D from BC

    D from BC Guest

    Maybe try:
    Just power it up with 10Volts..
    Just something left over from my audiophool days :)

    D from BC
  10. Well, this is puzzling. If the record levels, as shown on the "VU
    Meters", are okay, then the recording should be okay.

    How about you post the audio file somewhere where we can all listen to
  11. Rich Grise

    Rich Grise Guest

    I built one of these once, albeit I don't remember the component values

    It was a Radio Shack dynamic, marked "600 ohms", for what that's worth.

    It boosted the mic so that the sound card could "hear" it. One difference
    is, I dropped RL, replaced RC with a pot, and connected CL to the pot's
    wiper, then went right from CL to the sound card input.

    Good Luck!
  12. jasen

    jasen Guest

    I found this helped with a 600 ohm microphone.

    tip ---------+-[4m7]-.
    | |
    \ |
    0.1uF \| | || 2.2uF
    |/| || \_ |
    /~ BC547 ( )|
    | /~ |
    sleeve ------+-------------------'

    1 simple
    2 draws power from the soundcard

    1 performance varies from mediocre to bad
      depending on parts and temperature

    try differemt resistors 3.3M 3.9M 5.6M etc

    | This is an ascii schematic, if the diagram appears garbled |
    | try switching to a fixed-pitch font (courier works well) |
    | pasting it into notepad works well on ms-windows. |
    | in google groups selecting 'fixed font' (top right of page) |
    | or view source (options) work too. |
  13. Guest

    jasen ha scritto:
    Hi Jasen - thanks for your help!
    One problem only, I'm slightly confused on the diagram (even reading
    it at fixed-width):
    1) the component labeled 4m7 is a 4.7 mOhm resistence?
    2) I see the label 0.1uF but I dont see the condenser in the drawing!
    3) the "thing" at the right represents the soundcard?
    4) your comment " try differemt resistors 3.3M 3.9M 5.6M etc" meaning
    in place of the 4.7 milliOhm?

    .... sorry, but as I told before, I'm not exactly a great-master in

    thanks for your help!

  14. jasen

    jasen Guest

    oops! should be a big M there 4.7M Ohm resistance.
    that was an accident in editing, there is no second condenser.
    ignore that.
    that's meant to be the microphone.
    Sorry, as above, that was intended as megaohm.

    Revision 2: (use fixed-pitch font)

    tip ---------+-[4M7]-.
    | |
    \ |
    \| | +|| 2.2uF
    soundcard |----+----||------------.
    mic socket |/| || \_ |
    /~ BC547 ( )| mic
    | /~ |
    sleeve ------+--------------------------'

  15. Rich Grise

    Rich Grise Guest

    You've drawn this backwards! It should be:

    .-[4M7]-+--------- tip
    | |
    | /
    2.2uF ||+ | |/
    .------------||----+----| soundcard
    | _/ || |\| mic socket
    mic |( ) BC547 ~\
    | ~\ |
    '--------------------------+------ sleeve

    The signal should go from left to right, just like we read. :)

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