The STAX SRM-D10 Battery Powered Electrostatic Headphone Amp/DAC.
It is the world's first compact portable electrostatic amp/DAC. Now, you can enjoy the freedom of using all modern Stax electrostatic headphones (PRO bias) anywhere you go. The built-in High Res DAC is capable of playing music files up to DSD128. It also has a 3.5mm analog input.