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Thread: How to combine a mono and a stereo line inputs

  1. #1
    Senior Member
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    How to combine mono and stereo line inputs

    I'm making a guitar effect "pedal" based on Teensy 4.1 and the Audio Board.
    It also has a Line Input, for "play along".
    The problem is that the guitar has only one channel, but I have to split one channel into 2 separate preamps only not to cross-connect the stereo Line In.

    Is there a better way? How do I add one guitar channel to the 2 Line In channels without mixing the 2 channels together.
    Hope I'm explaining it right. I want to have a stereo Line In and add one guitar preamp to it.

    Thanks
    Last edited by Andy Belov; 07-21-2020 at 03:49 AM.

  2. #2
    Senior Member
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    Assuming whatever's driving the line inputs is low impedance output, there won't be a problem passively mixing in the signal to
    each channel. Something like a few k ohms resistors would be suitable.

    Most audio equipment these days is has output impedances around a 100 ohms or so, and input impedance of 10k to 50k.

  3. #3
    Senior Member
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    Mar 2019
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    Hoboken, New Jersey, USA
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    Silly me, totally forgot about it.
    Looked it up and see the resistors suggested ranging from 1K to 220K.

    What resistors would be good for the Teensy Audio Board?
    I guess 220K will loose more signal and 1K will add too much crossover, no?

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