Audio Hiss in simple microphone circuit, Need tips on reducing from someone who has done it before

Discussion in 'Wireless & RF Design' started by rubilacx, Mar 5, 2016.

  1. rubilacx

    Thread Starter New Member

    Mar 5, 2016
    1
    0
    Hi,

    We are building a fairly simple circuit to take a 4-6 Ohm aviation microphone and amplify it to a military headset. We are CLOSE, but there is a small amount of "hissy white noise" in the circuit that we are trying to get out.

    Is there anyone on this forum who has conquered a similar problem?
     
  2. #12

    Expert

    Nov 30, 2010
    16,283
    6,795
    I would guess, "yes". Probably half of us.
    The first problem is that we can't guess what circuit you are trying to use. How about a drawing of the circuit?
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,006
    3,232
    It may be possible to reduce the noise but, without seeing your circuit, it's not possible to give a good answer.
     
  4. Ramussons

    Active Member

    May 3, 2013
    557
    92
    The main source of a Hiss in low signal amplifiers is Thermal noise from Resistors and Shot noise from Semiconductors.
     
  5. #12

    Expert

    Nov 30, 2010
    16,283
    6,795
    That is the puzzle here. With a source impedance around 5 ohms, that circuit should be a slam-dunk. I hope the Original Poster wasn't a, "drive by" who will never be heard from again.:(
     
    Evanguy likes this.
  6. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,535
    1,251
    Sounds like a job for a common base amp, popular in home-built intercoms.

    ak
     
  7. #12

    Expert

    Nov 30, 2010
    16,283
    6,795
    I'd really like to see that compared to a j-fet input for noise quality. (I need the education.)
     
  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,535
    1,251
    No clue, but probably not as good. It strength is using an 8-ohm speaker as a current source, turning the low impedance into an advantage. In that application it is better than a traditional voltage preamp.

    ak
    intercom.gif
     
    #12 likes this.
Loading...