The Audi cable has 10 pins at the Phatbox end and nine at the head unit end this is because the audio input is changed from separate left / right ground to a common ground mid cable (pin 18).
Pins 10 -16 - 17 supply the power and ground IIRC 16 is always on & 17 being the trigger not sure if its a constant or a pulse trigger the phatnoise does not use pin 6.
Multi-pin connector I, 20-pin - black connector at the back of the Symphony II.
1 - Line output - left rear, to Amplifier R12
2 - Line output - right rear, to Amplifier R12
3 - Line output - Ground, to Amplifier R12
4 - Line output - left front, to Amplifier R12
5 - Line output - right front, to Amplifier R12
6 - Switched positive to Amplifier R12
7 - Infotainment CAN-Bus - High
10 - CD - Ground, to CD Changer R41
12 - Infotainment CAN-Bus Low
13 - CD data input from CD Changer R41
14 - CD data output to CD Changer R41
15 - CD-Clock from CD Changer R41
16 - Battery positive (B+) - Terminal 30 to CD Changer R41
17 - Switched positive to CD Changer R41
18 - Line output - Ground, to CD Changer R41
19 - Line output - left, from CD Changer R41
20 - Line output - right, from CD Changer R41
Phatnoise/ CD - Pin/Wire locations. Depending the on cable I have seen 2 colour codes there may be more i have seen a bit of confusion where people follow the wrong colour code .
Pin 13 = Green or orange
Pin 14 = Black or pink
Pin 15 = Orange or Black
Pin 16 = Violet or blue
Pin 17 = Yellow or yellow
Pin 18 = Blue or brown / black
Pin 19 = Red or white
Pin 20 = White or red
Pin 10 = Brown or brown
If the cable looks ok then its probably the coding