quick question about 2.5mm wiring

Discussion in 'The Projects Forum' started by magnet18, Mar 19, 2011.

  1. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    OK, I'm still building that plasma speaker, and on the schematic
    [​IMG]
    There is a positive and grounded audio input.
    The standard headphone jack is wired like this
    [​IMG]
    So my question is, is the negative line on the schematic supposed to be connected to the center neutral pin, or to the base (-) pin?
    Normally I would just try it and see, but I really don't want to risk blowing anything.
    Thanks! :D
     
  2. debe

    Well-Known Member

    Sep 21, 2010
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    Conect the headphone + to audio in (yellow). Headphone -- to audio in (blue) Neg.
     
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  3. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Thankyou! :)
     
  4. Adjuster

    Well-Known Member

    Dec 26, 2010
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    The arrangement of a 10kΩ pot. and 2.2kΩ series resistor at the input looks odd. It might not not wary the level much, unless the signal source impedance was quite high. This will not be the case if you are planning to use something like an MP3 player headphone output.
     
    Last edited: Mar 19, 2011
  5. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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  6. Audioguru

    New Member

    Dec 20, 2007
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    The original Instructable does not have a schematic. The copy that you are copying might have something connected wrong like the backwards polarity shown on the audio input capacitor.

    You are connecting only one channel of the stereo input. Maybe you should mix both channels in two resistors to make mono.
     
  7. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Yes, I noticed that, it's not actually backwards but it appears to be just poorly drawn, In any case I fixed it when I noticed I had it backwards. Positive to the audio, negative to the chip, correct?

    I thought about that, but I don't know enough about audio to mix them to make it mono, hopefully I can switch my computers settings to mono-out, or just use a mono file.
     
  8. Audioguru

    New Member

    Dec 20, 2007
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    An electrolytic polarized input capacitor alway has the negative wire connected to the input source and the positive wire connected to the chip.
    Because most input sources are at 0VDC and most chips have a positive voltage.

    Two resistors make an audio mixex to convert stereo to mono. one resistor from each audio channel. They join and do the mixing at the input of your gadjet.
     
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  9. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    thanks, I'll switch it... again

    What values should I use?
     
  10. Audioguru

    New Member

    Dec 20, 2007
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    One 560 ohms resistor from each channel of the earphones output connected together at the signal input of your circuit makes mono.

    The real schematic shows the polarity of the input capacitor correct, the pictorial schematic shows its polarity wrong.
     
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