It is sanded off, and considering how many copy cats are in the game, I think it is every company's prerogative to protect their small or large investments in research and development by hiding what they can from the copycats. In Europe and North America you don't see so many copy cats, but here in Asia, especially China, Korea, and Japan, there are so many small companies trying to rip off the biggies. The Japanese will tell you they don't copy - that they never have, but dear me... they are blind.
Anyway, I have no idea what the op-amp is.
The better the source you can connect to the T1, the better, just like any amp. The T1 has a nice enough circuit that it can reduce hiss from poor sources or expand the line outs of good gear. If the volume gets fixed, even line-level outputs will be easy to handle.