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Stereo to mono adapter

Discussion in 'General Electronics Discussion' started by yagsirepusrj, Jul 7, 2011.

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  1. yagsirepusrj

    yagsirepusrj

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    Jul 7, 2011
    I'm trying to make and adapter that would go from a 1/8th inch stereo jack to this mono headset and just want to make sure I get this straight. Is all I need to do is to add a low ohm resistor to the left stereo output and one on the right output and bridge them together? Here is the schematic for the headset I'm trying to use.
    [​IMG]
     
  2. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Yes. that's all that should be needed. I'd suggest using resistors somewhere between 12 & 22 ohms.
     
  3. yagsirepusrj

    yagsirepusrj

    3
    0
    Jul 7, 2011
    Thanks for the reply but do you have an explanation on why I should use on of those. I'm new to this stuff and I'm just trying to figure out how and why it works
     
  4. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Modern headphones usually have an impedance of 32 ohms, and the resulting load should end up somewhere in that vicinity. I'tll be a compromise but it's not critical.
    The resulting impedance after the stereo-mono adaptation will depend on the phase of the stereo signal, where low frequencies are usually in-phase while high f's are not.
    The impedance of your present headphone is 19 ohms / 2 = 9.5 ohms.
    For in-phase signals the ideal resistor values are: ((32 ohms / 2) - 9.5 ohms) * 2 = 13 ohms.
    For 180 degrees out-of-phase signals the ideal resistor values are simply 32 ohms.
    To retain maximum volume it's best to use low resistor values though, and its at low frequencies where it matters most anyway (where the most power is present).
     
  5. MagicMatt

    MagicMatt

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    Jun 15, 2011
    Something to be aware of converting stereo to mono is whilst what you're doing works from an electronic point of view, it often fails from a sound point of view. Modern recordings often use "Stereo Wideners" which create out of phase signals to throw sound beyond the speakers. If you combine them the way you are, they often cancel each other out to some degree, so you may find the balance of sounds changes significantly and some instruments sound much quieter than normal.

    Presumably you're leaving the microphone disconnected, or taking it to a seperate jack?

    You're probably already aware, but the schematic you posted isn't a stereo jack, as it has 4 poles not 3. It looks like the ones that used to come with the foreign language teaching machines I used at school.

    Unless this is a very high fidelity headset, or you're doing this for the experience/learning, I must admit I'd just go get a Skype headset which will be stereo and have a mic on a seperate jack (I use mine with a Minidisc as they're very universal headsets).
     
    Last edited: Jul 9, 2011
  6. yagsirepusrj

    yagsirepusrj

    3
    0
    Jul 7, 2011
  7. MagicMatt

    MagicMatt

    70
    0
    Jun 15, 2011
    Cool! You did have me curious! I really couldn't work out why you'd want to do what you were describing, but it makes sense now.:)

    My solution to that when I did some work on a building site was just to wear my little "in the ear" things under the ear defenders... but then I have an aversion to spending money.
     
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