Hi Kevio,

E5 is a Portable Headphone Amplifier designed to improve the sound quality and volume of any Digital Audio Player such as a MP3 or MP4 Player, Mobile Phone, Laptop, or Notebook. It is an upgraded model of E3 Headphone Amplifier which is very popular around the world. It retains all the advantages of the E3, and yet still has very small slim case! Now with a volume control so you can connect directly to the line out of a Digital Audio Player and control the volume directly!
But it is more than just an upgraded version of the E3! It has a higher power output, better Signal to Noise ratio and Lower Distortion! And with the new TI’s headphone amp solution, E5 have better sound qualilty and can work better with high impedance headphone. With a sound effect switch which will remove any Bass Boost., E5 will be a good pair with more different headphone.

http://fiio.com.cn/en/showproduct.asp?id=309