The supply voltage of the AD8616 is insufficient to handle the output of the WM8740.
Possible solution is
1) Redesign the power supply so that the supply to the Ad8616 is at least 5v or more
2) Reduce the gain of the AD8616 so that the output is within the supply limit
(the so called 2.2K resistor mod)
3) Reduce the signal feeding the WM8740 DAC so that the output is below clipping level. Setting iTune, (Windows media player or VLC) volume to 80% or lower.
If you are using line in, you are not affected.
