I wired in a female 3.5 connector as you did, but for the mic and tested two different mic types in hopes it would help. Neither helped, always came back with a weak output. I believe the built-in amplifier just isn't robust enough for higher amplification. Heck I went so far as to add a amplifier after the PCB, still no luck, hence the reason I've been watching this thread to let someone else beat their head against the wall for a while Maybe you'll have better luck.