Microphones Direct to Headphones - Audio Amplifier?

Discussion in 'The Projects Forum' started by yugi4542, Nov 2, 2014.

  1. yugi4542

    Thread Starter New Member

    Jan 30, 2014
    4
    1
    I'm attempting to build a circuit in which audio from two separate electret microphones are amplified separately and piped directly to the left and right channels on headphones (kind of like a complicated hearing aid). I'm relatively inexperienced with audio projects, and was wondering if anyone had any suggestions on an amplifier that might work for my needs?

    I built a working prototype with 2 LM386 ICs from RadioShack, but I'm looking for something I could buy in bulk to make a small production run in a year or two if my idea works out; I just have no idea where to even start looking for that information other than asking other, more knowledgeable people.

    Ideally, I'd like an amp with low noise that's simple to wire up. Being able to amplify both channels through one amp would be even better.

    Thanks for your suggestions in advance! :D
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,085
    3,024
    You need a stereo audio power amp IC. If you search on that, you'll find lots of options. Basically fancier versions of the LM386. Someone here will hopefully name some of the favorites for you.
     
  3. DickCappels

    Moderator

    Aug 21, 2008
    2,647
    631
    What kind of headphones? Some earbuds can produce over 100 db SPL at 1 milliwatt and an LM380 or other speaker amplifier would make a dangerous combination with such transducers.

    Can you provide more details about your earphones and how you plan to use this device?
     
  4. yugi4542

    Thread Starter New Member

    Jan 30, 2014
    4
    1
    Thanks for the advice! I'll keep it in mind.

    To be honest, I hadn't given much thought to the headphones being used. They will likely be small earbuds that clip on to the ear (workout headphones or the like), but that decision would be up to the person wearing it.

    A friend of mine had a costume for Halloween that obscures his hearing almost completely, and I had the idea to rig up a pair of microphones on the outside of the costume's head, wire the audio feeds in to a control circuit with the amplifier chips, and pipe the separate amplified outputs to a female stereo headphone jack that my friend then plugged his headphones into so he could hear directionally in costume.
     
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  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
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    Start at the headphones and work back. Start at the microphones and work forward...
     
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  6. DickCappels

    Moderator

    Aug 21, 2008
    2,647
    631
    You should be able to get what you want if you start with the circuit at this link.

    http://amplifiercircuit.net/electret-microphone-pre-amp-based-ne5532.html/electret-mic-pre-amp
    [​IMG]
    I suggest making the following changes:

    C1 to become 22 uf or 47 uf
    R3 to become a 50k variable resitor
    C4 to become 100 uf
    R5 to become 1k
    C3 is probably not needed, but can be used to roll off the higher frequencies if you want.
    If you want stereo, use the TL072 or TL082. Many other opamps such as the lowly but still useful LM358 will also work.
     
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