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Making a mic pre-amp

Discussion in 'Pro Audio Equipment' started by z120129, May 31, 2007.

  1. z120129

    z120129 Guest

    Hey - I am interested in learning about the internal workings of mic pre amps. Obviously, one of the best ways to do this is to build one from scratch. after i get comfortable, i want my final project to be a stereo pre. what kind of things really make or break a mic pre? some of the things i am thinking of adding would be a M/S decoder on one channel, DI on both inputs, switched gain (with continuous knobs for trim), obviously phantom power on both. what else would you add to a pre amp to make it stand out ?
     
  2. Boswell

    Boswell Moderator Distinguished Member

    My recommendation would be to build a good preamp in kit form first, then consider designing and building your own. The Green preamp is a good compromise between sound quality, features and ease of building.

    You'll find several like-minded construction folks and info on the Green preamp over at the Prodigy Pro forums.
    http://www.prodigy-pro.com/forum/viewtopic.php?t=5150

    Good luck, and let us know how you get on!
     
  3. therecordingart

    therecordingart Well-Known Member

    http://www.groupdiy.com - They'll teach you everything you need to know

    http://www.seventhcircleaudio.com - Awesome preamp kits to build if you don't know how to make your own PCBs and don't want to source your own parts
     
  4. z120129

    z120129 Guest

    im asking more about after i learn about the basics, what features would be cool to add(so i can start learning about them now)
     
  5. Boswell

    Boswell Moderator Distinguished Member

    "The basics" includes learning about what features are useful and what are not. I would start there.

    Actually designing a good preamp with those features is several levels up in competency after you have mastered the basics. Things like switchable HP filters, selectable M-S decoding (which involves two-channels not just one) and variable clip level indicators are all things that feature-rich preamps would offer after the standard items of gain trim and phantom power out.
     
  6. audiotec

    audiotec Guest

    You might want to check out PAIA kits for a basic preamp kit at http://www.paia.com/ to learn basics. These are not high end, but good for experience.
    _____________________

    http://audiomusicalresources.com
     
  7. Kev

    Kev Well-Known Member

    go to Group DIY and look at the Metta Threads

    JLM Audio
    and as mentioned above
    Seventh Circle
    Green Mk1 and Mk2
     
  8. Link555

    Link555 Well-Known Member

    The Pre-amps I have designed in the past have been pretty simple. The main points I typically concentrate on are:

    1)The power supply-very import to get a very clean rail or rails.

    2)The differential Input to Single sided converter-Either XFMR or solid-state. OR you could make completely differential amplifier, much more difficult.

    3)The Amp itself-Opamp, FET, Tube etc... Your choice

    4)Differential out put conversion- xfmr or solid state.

    5)The Phantom Power supply- Make sure you have enough current to drive your mics.

    6)A Polarity Switch-This one is typically a simple wiring change.

    7)A Pad -lower the gain of the amp.

    8)A High Pass Filter- Usually tuned at 80Hz typically 2nd order.

    After those are good, and then if you still wish to add gimmick features, go for it. Although for your first time I think you will have enough on your plate.

    Get access to an oscilloscope, and waveform generator, multi-meter and a decent soldering iron.
     

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