Some photos on instagram:
It's an MXR Headphone Amp circuit I got from the excellent tagboardeffects layout webpage:

Sounds pretty good!
Wouldn't recommend using without an amp sim/cab sim up front as it's very neutral sounding in an unsurprising "guitar into mixer kind of way", but with the Harley Benton American Sound (Tech21 Blonde clone) up front it sounds good to my ears!