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Please help! Microphone preamp needed.

Discussion in 'Electronic Design' started by Lynton, Aug 18, 2004.

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  1. Lynton

    Lynton Guest

    Hey chaps. I've been searching high and low, and the only commercially
    available mic preamps I can find are all over $250, which I can't
    really justify spending. I'd love to buy a kit and have a bash at
    doing it myself, but I've never done any electronics before, and I
    feel like I'm in over my head! Basically, what I'm after is a preamp
    that provides up to around 40dB gain. I want one powered by a 9v
    battery, is stereo, has 3.5mm in and out jacks, a hard case to protect
    it, and if I'm lucky a gain adjusting knob. Does anyone know where I
    can find the plans/kit for such a device? I live in Adelaide,
    Australia, and I'd be more that willing to pay someone to assemble it
    for me if it's a complicated custom job. I really don't want to have
    to take the suckers option and shell out the $250 for something that
    could probably be built for a lot less. This is the one I'm
    considering purchasing:

    Any help or ideas would be very much appreciated.


  2. Rich Grise

    Rich Grise Guest

    If you're interested in learning to solder and work with other hand
    tools, and build it yourself, you could check with some of these websites:

    If you're looking for someone to build it for you, ask around tech schools
    or ham radio clubs or anyplace where techies hang out.

    Have Fun!
  3. Pooh Bear

    Pooh Bear Guest

    You can build a *pretty damn good* mic amp for maybe $3-5 in active
    parts. One that has a thermal noise figure at max gain of little more than
    2dB. Gain is easily variable over a 45 dB range. Typically 15 - 60 dB

    You *won't* acheive this on a 9V battery though ! You'll need split
    supplies of typically +/- 15V ( the more the merrier ) but less than the
    voltage limit of the op-amp ( usually +/- 18V for commercial parts +/-22V
    for industrial ). I use +/- 17V.

    Best performance for mic amps is achieved with balanced inputs on an XLR

    3.5 mm jack plugs / sockets are unsuitable for high quality audio due to
    poor contact noise / resistance / intermittencies.

    If that interests you, I can point you to a schematic.

  4. Can you point me to a schematic for a matrix mixer?

  5. Well, you can get little complete mixers for way less than this., this one is about 40 uk

    Kevin Aylward
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
  6. Take a look at Rane's web site.
  7. Might this help? See page 7.
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