Recording headset mic, speaker and ambient sound

Discussion in 'The Projects Forum' started by hang4, Jan 22, 2012.

  1. hang4

    Thread Starter New Member

    Jan 22, 2012
    2
    0
    I am a hang glider pilot and I make video recordings of my flights. I would like to be able to narrate those videos in flight. I also have a retrieval driver following me and I talk with him via a ham radio. I would also like to record those conversations as well. (He would be aware we are doing it, so no legal issues) I have speakers and a mic built into my headset that is connected the the radio and I'd like to be able to share that connection to feed a voice recorder that has a external mic jack.

    In essence there would be three "sources";

    - mic direct to voice recorder - would be active when radio is not
    - mic to voice recorder when PTT is active
    - Speaker (Radio receive) to voice recorder

    I am pretty sure I can just split the mic to go to the radio and recorder, but I can't get my head wrapped around how to get the speaker signal into the recorder without everything melting or some other bad outcome.

    A diagram is attached.

    Any help would be greatly appreciated

    Thanks
     
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Without any details then we are guessing about the level at the earphones, their impedance and the impedance at the input of the mic preamp.

    The earphones level might be 100 times too high to feed the mic input on the recorder so it must be attenuated then feed a mixer circuit that mixes the mic signal with the earphones signal to feed the recorder.
    An active mixer circuit might be needed if the loss of a passive mixer (simply using resistors) is too high.
     
  3. hang4

    Thread Starter New Member

    Jan 22, 2012
    2
    0
    I don't have the exact specs for what's in the helmet, but the radio specs are:

    Audio out - 0.4 W @8 ohms for 10% THD (@7.2V)
    Mic - 2-kilohm condenser

    I looked for other compatible headsets and they are very consistent about the 2k ohm for the mic. On the speaker side, they seem to all be 32 ohms.

    I am far from an EE - so I am not sure if I am answering your question.. but that's about all I could find.
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    How about setting up a second microphone to catch all your speech, and mix off the radio output to catch the other side speech? That takes the PTT and input impedance of the radio out of the loop.
     
  5. K7GUH

    Member

    Jan 28, 2011
    191
    23
    Check into anti-noise mikes. I know they make them for modern aircraft. If all else fails, use the WWII technique of the throat mike. You may need a pre-amplifier on the mike input(s) and some kind of impedance matching on the recorder input. You don't need an EE degree to make things work.
    Another idea: if you have normal hearing, there is enough signal from your voice going out through your ears to make a reasonable attempt at an in-flight audio source.
     
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