i think i doesn't have a built-in mic, but, surprisinly, the manual tells about one. Just to add some confusion CL561-CH1-rev3.doc
pag. 2, line 33, under "I/O Ports" section:
w One MIC In port
pag. 5, line 21, under "Audio CODEC Realtek ALC250" section:
2 MIC inputs: Software selectable.
So, I don't know if it's an abandoned feature, but i think you guys should know.