Pros: Clean, balance, can drive 4 headphones at the same time, cheap
Cons: Not portable
This is the amp I am looking for. It is better than any portable amp which costs around 200USD.
It can substantially enhance the soundstage, the speed and the bass of your headphone.
I am using it to drive my RS1i and it's perfect. BTW, It works great with any device I plugged in.
I even tried apple's earbud and it suddenly become my favorite earbud.
However, I still hope you can distinguish its quality with your own ear rather than sb. else's reviews.