Fiio K3 is a new for 2019 usb dac + headphone amp. It has its own volume dial, low and high gain switch (for earphones & headphones), bass boost option and is a balanced amp design, with a 2.5mm output, as well as a 3.5mm out.
Perfect to use with work computers that do not allow you to download drivers, there is a switch on the rear panel for usb 1, universally compatible driverless connection with apple and windows, as well as usb 2, for high res 24 bit file decoding.
K3 uses a very good AKM dac chip, AK4452, as its core. USB connection is the new standard, usb-c. The volume control is highly accurate, providing even balance even with very sensitive earphones at low volumes.
The K3 feels solid and nicely made, is the size of a mint tin and takes up very little desk space. Fiio K3 has line out, optical out and coax out, making it easy to connect to any powered speakers you have.