I just tested my PDB's audio part, which is a "reflow" of Paul's Audio Board.
The Guitar sketch works (synthesis), line input, phones, lien out work.
The microphone works, but the sound is like the "phaser" guitar effect, like it's going though a long paper tube, like "bouncy" sound.

Does anybody have a clue?
Here is the diagram and the PCB part for the audio.
I copied it from here (Schematic, Rev D): https://www.pjrc.com/store/teensy3_audio.html
There is a mistake there: RX and TX are reversed connecting to pins 7 and 8.

Click image for larger version. 

Name:	Schema.jpg 
Views:	7 
Size:	139.0 KB 
ID:	18353 Click image for larger version. 

Name:	pcb.jpg 
Views:	3 
Size:	299.5 KB 
ID:	18354