The prodigiously-thumbed pioneering headphone reviewer, Sasaki, published his thoughts on the Portaphile Micro (in Japanese) the same day as yours truly. Here's a bit of trivia for you: what country houses both of us?

He seems particularly ecstatic, especially when comparing the MUSES Micro version to his older 627, which delivers a plainer, less exciting sound. My take is that the OPA627 version is better for a wide range of headphones, but both work nearly flawlessly for earphones.