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Mono to Stereo

Discussion in 'General Electronics Discussion' started by Tonko, Mar 29, 2012.

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  1. Tonko


    Mar 29, 2012
    Hello, I have a little problem...

    I am trying to wire up an ear piece so that both left and right audio go in the the single ear piece and not lose either channel. Essentially giving you stereo in to the one ear.

    I have already separated my ear piece and now have just won cable with Signal and Earth (red and copper). But when I connect Left and right Signal from the source to the mono signal and earth to earth, I am getting some funny results....

    If I use my PC as a source (the headphone jack on my speakers), It works perfectly through the earpiece but I still hear my speakers faintly outputting sound...

    Also if I use my SanDisk Sansa mp3 player as the source then the Audio seems to rhythmically cut in and out every second or so...

    But all works well with the iPhone as the source.....

    As you in can imagine its the SanDisk Sansa that I need this project for....

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Wiring the two stereo signals directly together to one speaker does short circuit the outputs of the two amplifiers. The effect of this obviously depends on the amplifier you are using (PC, IPhone, Sansa...).
    The best way would be to insert a summing amplifier between the output of your sound generating device and the mono earphone.
    If you don't want to or can't, try inserting a small resistor between the stereo wire and the summing point (where both channels meet at the earphone's speaker).
    The value if the resistors depends on the impedance of the speaker. Start with 1/4 of the impedance of the speaker.


    Attached Files:

  3. Tonko


    Mar 29, 2012
    Thanks for answering so quickly.

    I found a non-electrical solution....

    The Sansa has an option to turn the FM radio output (which is what I need it for) in to mono - So I just soldered earth to earth, and red to red and left the green one not connected to anything (although it appears its sending joint signals to both wires so I could have used either). So with a bit of heat shrink no one will ever know ;)

    Thanks again for the reply.
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