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Custom Headset Adapter

Discussion in 'General Electronics Discussion' started by ShowMeCablesDrew, May 11, 2012.

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  1. ShowMeCablesDrew

    ShowMeCablesDrew

    3
    0
    May 11, 2012
    I am going from 5pin din to TRRS.. (please see attached photos)

    tip - left audio
    ring 1 (closest to tip) - right audio
    ring 2 - mic
    shield - ground


    Tip------------------------5
    Ring1----------------------4
    Ring2----------------------1
    Sleeve---------------------2

    With the two grounds (pins 2 & 3) tied together. This is the best method I can think to do this. I asked a few of my colleagues and one of them expressed some concern that tieing the mic in and audio out ground could cause quite a bit of feedback. Some equipment will work fine like this, but other equipment will not function properly.

    I was wondering if anyone has ever tried anything like this, or can offer any insight as to whether this will work or not.

    Thanks!
     

    Attached Files:

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    10,090
    2,157
    Nov 17, 2011
    Your colleagues are right. If you have a chance to feed different grounds for mic and audio aou: do it.
    If both share a common ground, any current though audio out will generate a small voltage drop on the GND wire because this wire has a nonzero resistance. This voltage drop will be amplified by the microphone amplifier. In the worst case you get a feedback loop as this amplified signal is returned to audio out.

    Harald
     
  3. ShowMeCablesDrew

    ShowMeCablesDrew

    3
    0
    May 11, 2012
    Meh

    That's what I was afraid of. What if I soldered a wire onto pin 3 of the DIN connector and grounded it somewhere on my bike? (this is to connect a headset that has a TRRS connector to my Goldwing motorcycle that has the 5pin din connector for its intercom system) That way everything is grounded, but they're not tied together.

    Thanks.
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    10,090
    2,157
    Nov 17, 2011
    A separate wire can make matters even worse. While reducing DC resistance, it is an inductor with AC impedance plus it is an antenna (since it is not shielded within the cable assembly).
    I suggest you try your scheme and test how big the influence from audio out to audio in is. Maybe it is tolerable. Since you mention using this setup on a bike, there will so much noise from the outside that the feedback probably will be all but inaudible.


    Harald
     
  5. ShowMeCablesDrew

    ShowMeCablesDrew

    3
    0
    May 11, 2012
    That's very true.. I didn't even think about the wind noise. It just may be enough to conceal some, if not all, of the feedback.

    Another possible problem raised to me was connecting a 3.5mm plug to a 5pin din jack and the power handing difference between the two being an issue. I was told that 5din jack will put out more power than what a 3.5mm plug can/will handle and that I should be cautious connecting the two. I know I don't have any specs of the system the 5din is coming from, but does this sound like it has any legitimacy to it?
     
  6. Harald Kapp

    Harald Kapp Moderator Moderator

    10,090
    2,157
    Nov 17, 2011
    It's not an issue of the type of connector. The DIN type can handle emough power for that purpose. What you have been told is most probably connected with the system standards (voltage levels, current levels and resistances) which typically differ between components using DIN connectors and components using Cinch or 3.5 mm plugs.
    Without concrete technical data you'll have to give it a try, The chances are very very small that something is destroyed due to this issue. Worst case is that either everything is too loud or too hushed.
    If it's too loud, some series resistors can help.
    If it's too hushed, you will need an amplifier.

    Harald
     
  7. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    Balanced and unbalance audio mixing as well, you can create some crazy feedback loops with the ground if you don't design it properly...
     
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