Need to make a good quality mic amplifier.

Discussion in 'The Projects Forum' started by kuera, Jul 1, 2016.

  1. kuera

    Thread Starter New Member

    Aug 17, 2012
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    Good evening.

    Short story here. Im trying to find a circuit to make a decent audio amplifier. The idea is to amplify a mic plugged into an audio jack so that I can plug earphones into the output and get sound with very little distortion and volume control. Also trying to make this portable so low voltage is a must (5 or 9 volts, to either use rechargable 4AA batteries or 9v batteries). The application is basically a hearing aid. I know it seems very retro but its something im toying with for an almost deaf family member and while I enjoy messing around with electronics my understanding of it is basic at best and limited to building kits with some random tweaks.
    I would really appreciate help with this if possible and patience with my limited understanding ^.^
    I did find advice on using an LM386. Is this alright or is there a better IC to use?

    Many thanks in advance if you took the time to read this and answer.

    Gordon
     
  2. Lestraveled

    Well-Known Member

    May 19, 2014
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    First, what kind of microphone will you be using? (Dynamic, electret, etc.)
     
  3. kuera

    Thread Starter New Member

    Aug 17, 2012
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    0
    Damn you're quick :D
    Well im not sure of the exact difference but I was messing with a electret. The idea is that I can plug in a normal pc/laptop mic or use a 3 mm audio jack and plug it straight into some other audio output like a phone or radio just to let her hear either general conversation with the min plugged in or the radio jacked into it.
    Sorry I cant give more technical needs but ill try with what I know
     
  4. Lestraveled

    Well-Known Member

    May 19, 2014
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    @kuera
    I was about to post a schematic of an amplifier but it sounds like you would do better with a kit or a pre-built board.

    How about, search on EBay for "headphone amplifier board". You will see a lot of options and some pretty cheap prices.

    How does this sound??
     
  5. kuera

    Thread Starter New Member

    Aug 17, 2012
    21
    0
    I'll take a look.
    I did brows around a few local electronics stores for a kit but had no luck. I wanted to leave ebay as a last resort due to the fact that in SA getting anything posted that isnt from here takes and age and not even sure it would arrive.
    If it wouldnt be too much trouble would you mind posting up that schematic you were referring to? I'm trying to self learn all this stuff and it would give me a nice chance to play around with the gear and components I've hoarded like a pack rat.
    Thanks for replying and what you've done so far.
     
  6. dannyf

    Well-Known Member

    Sep 13, 2015
    1,825
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    electret mics come with some amplification built-in, through a jfet.

    You may also salvage a mic from cell phone heatsets (wired types). They come with everything wired up and all you need to do is to provide amplification.

    Most opamps can do that, and do that very well. Tricks come in in terms of handling gains under different loudness or background noise, which you may or may not care.
     
  7. bertus

    Administrator

    Apr 5, 2008
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  8. Lestraveled

    Well-Known Member

    May 19, 2014
    1,957
    1,215
    @kuera

    Gordon
    There are plenty of low voltage headphone amplifiers on the market but that would require you to order them. So, the challenge is to build a headphone amplifier that runs on low voltage from low tech parts.

    If you could increase your operating voltage to 10 - 12 volts, this circuit could get real simple, real fast.

    Download the data sheet for an LM380. Its minimum voltage is 10 volts. It has been in use for 30+ years. It uses very few parts.

    What do you think?
     
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