I gave my GameBoy Advance SP a headphone jack 16 years later. It was never released with one and I had never seen anyone do it until I saw a YouTuber by the name of Makho do a video on it (https://www.youtube.com/watch?v=L5i0NNrpfFw&t). I know there is probably better, more professional ways to do this but I am not an expert and im just showing you my way of doing it!
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