Great Chris! Good workl!
I didn't know this headphone amplifier, and believe me, i was looking for it several times, but i always fail to choose the right one. I try several amplifiers modules based in the PAM8403, but i didn't get a good result.
So, it's great that you have founded. Could you document your work a little bit more in detail and add some photo, perhaps in a new topic with a good title so everybody can find it easily?
Thanks a lot!