Earphones/headphones from the junkbox

Discussion in 'General Electronics Chat' started by atferrari, Mar 2, 2014.

  1. atferrari

    Thread Starter AAC Fanatic!

    Jan 6, 2004
    Earphones and headphones.

    Audio was / is one of my stumbling blocks. I am at lost here.

    I need to test a small directional microphone whose sensitive element is an electret mike.

    I collected earphones / headphones for years, some probably from OLD hearing aids or portable radios, walkmans, cellular phones, CDs reproducers, even those given away by airlines and much more unknowns. The awful diversity of their jacks (or are they plugs?) I find it overwhelming.

    Any simple way or rule of thumb, to get a rough idea of their impedance, if that matters at all, and to select one or two I could use, no risking to damage the audio amp? Sole thing I know for sure I can forget stereo.

    BTW, I am going to build a (tested-working) preamp for my electret mike. What should follow? Maybe my LM386 based amp that works OK with an 8 Ohms speaker?

    The unavoidable suggestion to Google, is surely to be followed later by an equivalent amount of critics on the circuits I could propose.

    For the moment I would prefer a one / two chips solution.

    Gracias for any help.
    Last edited: Mar 2, 2014
    PackratKing likes this.
  2. KJ6EAD

    Senior Member

    Apr 30, 2011
  3. #12


    Nov 30, 2010
    The end of the wire has a plug on it. The hole in the box is a jack.
    You can slap an ohm meter on just about anything. "Low" impedance is called 600 ohms but you might only get the DC resistance of a coil. Anything else is high impedance. If you see several k or nearly infinity, you can be sure it's called high impedance.

    We've had several threads about the 386 being noisy. Perhaps a TDAxxxx chip or a nice, quiet, TL071 and a fixed gain of 20 on the LM386?
  4. BMorse

    AAC Fanatic!

    Sep 26, 2009