Adding a source to an existing closed radio/headset

Discussion in 'The Projects Forum' started by sydcomebak, Dec 13, 2011.

  1. sydcomebak

    Thread Starter Member

    Dec 13, 2011
    I will be adding photos as soon as I get home and can take good ones, but here's the situation: I have an existing radio/headset combo that I use at work. I have spliced in a new 1/8" jack to allow an alternate source to play through the same earpiece, but not all of the channels seem to come through.

    The wires to the earpiece: Yellow & Orange
    The wires from the stereo 1/8" jack: Yellow, White & an unshielded(ground?)

    Should I be looking into a specific type of 1/8" jack knowing that the earpiece is mono? The sources could be a variety of stereo items (mp3, phone, portable radio).

    Thanks everyone!
  2. tracecom

    AAC Fanatic!

    Apr 16, 2010
    If the earpiece is mono and the output from the new device is stereo, then you will have to combine the left and right channels in order to hear them both. In the best case, this would be done through a mixer circuit, but it is possible to simply connect the left and right channel wires together via two resistors, and connect that plus the ground to the earpiece. It's done all the time; google "stereo to mono".
  3. elec_mech

    Senior Member

    Nov 12, 2008
    Welcome to AAC!

    Some questions:

    Is this is wireless headset, e.g., battery-operated radio headset? Or is it wired to something? If yes, what?

    Where did you make the splice? Did you solder the 1/8" jack directly to the earpiece or to something else?

    What do you mean by channels? What are you trying to feed into the headset? Another radio, an MP3 player, etc.?

    Note you may need to feed the input through an amplifier then into the earpiece before you hear anything depending on the input signal type. Also, the input signal has to be, for lack of a better word, matched to the impedence/resistance of the earpiece. I'm not an audio guy, but cars used to use 4Ω speakers while many speakers found in your home theather are 8Ω and smaller speakers such as headphones may have 16Ω or 32Ω speakers.

    So you only have one earpiece/speaker on the headset not two?

    Tracecom is correct if you are feeding a stereo (dual) signal into a single earpiece. If you have two earpieces, then one of the signal wires goes to one earpiece, the other signal wire goes to the other earpiece and both earpieces share the ground connection to the signal.

    You could also use a mono 1/8" jack instead of a stereo one which should combine the two signals from a stereo input. Or just do what Tracecom suggested. :)
  4. sydcomebak

    Thread Starter Member

    Dec 13, 2011
    The headset in question:
    The idea is for the headset to remain as "stock" as possible so that casual inspection doesn't notice the difference.

    The end on the upper left is where the headset attaches to the radio, upper right is the mic/push-to-talk/accessory button. The center is the earpiece.

    I have already determined which wires/pins are for the audio to the earpiece. They are colored Yellow and Orange. I drilled a hole in the housing (UL) to slip in the wires that come from the external source. When I went to Radio Shack, I got this:
    Cut off the male end, and insert into the drilled hole.
    3 "wires" inside: White, Yellow, unshielded untwisted mess(Ground?).

    Just poking and praying, I found that yellow to yellow and white to orange produced sound, and if I twisted in the unshielded mess to the yellow/yellow, I got more channels, but not all where I could hear them WELL. Also, at full volume, it is about half what I would expect.

    I'd really like to avoid too many parts, because they all have to make it inside the enclosure again. If you are telling me that this:
    will pick up all channels and spit them out on 2 wires, then I'll head out to the shack right now. I have a torn apart earpiece to play with before I go ripping apart the one that kinda works right now.

    As far as the ohm rating on the speaker, I can't tell you. Suggestions?