On-ear (left and right parts have their separate ear-clip), pretty linear characteristics (no particular "bass boosting"), with an analytical, somehow "cool" (as opposed to "warm") output.
In my opinion, the Yuin G1A and G2A are excellent for classical and voice music, including solo instruments and quartets.
Enthusiasts of Hard Rock and Heavy Metal would be disappointed, though. They'd rather look elsewhere.
If your mobile audio device will not drive high impedance earphones, the G2A (low ohm) will do fine.
Last time I checked, the G2A was $49 in the U.S., around £45 in the U.K.
One can get Yuins from Hong Kong as well, see the offerings of your preferred auction house on the internet.
(Most portable devices will need a portable amp to drive the G1A, due to its high impedance. And it is way above the price limit)
Note: Both the G1A and G2A do *not* isolate the user acoustically, they let pass a good portion of environmental sound (and noise).