The jack is wired for mono (2-pin plug).? The audio is only mono, and if you were to wire both the tip and mid-barrel together in the jack, you run the risk of shorting out the LM386.? Confirm that it works with a 2-pin mono plug.? I use an external 3.5 mm stereo to mono adapter to connect my stereo headphones.
A complication is when your headphones have a built-in microphone, so the plug has four connections.? Since the mic connection is at the opposite end as the tip, the jack on the board thinks the mic connection is the common, and things will get funky.
