Originally Posted by Gordon Scott
The iPad input wouldn't handle stereo as it's a single mic only. Stereo headphone and mono mic.
You may also have an issue with the mic input being too sensitive for the keyboard output.
You might also run into issues as the microphone input provides power for the microphone (I believe around 1.5v). This isn't likely to damage anything you plug into it as there are likely current limits, however it may adversely affect the sound quality (adding a DC offset which could cause asymmetrical distortion). You can get around it by adding a capacitor in series to block the DC, but that can also adversely affect sound quality (it would act as a high pass filter and would affect phase).

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