Aiptek A-HD firmware 1.5, replaced internal mic test. Added 1/8" mic jack wired as MONO, tip signal, and (casing) neg/Grd, barrel (unconnected). Tested with Sima MZM-1 (setting zoom, setting this to "norm" is lower amplification, possible better for very even high SPL levels?), Also test with old Mono Sima "CamMike" SRM600 ohm. Both are low amplified powered mics with AAA or AA battery (1.5 volt). I've also tested the jack with a computer mic (not powered) and it works, but sounds close to the internal mic.

WARNING it's rather involved with heat sensitive and small closely placed together parts. You may search "digicam" and "aiptek" and "mic" maybe also "jack" to get some idea of how to do it **at your own RISK**
***update*** I found a MUCH better mic vimeo.com/994164