AmpTwo

A new module is up on GitHub. This times it's a dual stereo headphone amplifier, although it is 4 indepentant channels connected to 2 stereo jacks so you could do what you want with it really.

Design is a little over-complex. It has balanced to single ended buffers feeding two good old fashioned dual potentiometers. There is then an op-amp based class B amplifier for each channel. Gain is set at 0dB for initial testing as the ADAU1966 puts out good voltage, but gain could be increased where this is needed. 

I have used these type of headphone amplifiers before and they seem quite stable and they will burn out the headphones before you run out of volume/power... They can also drive small speakers if needed.

Design untest at the moment, and the 220pF capacitors on the op-amp negative inputs may be not-fitted or a different value in the end.