Could look at the Wavelength Proton DAC - in addition to Async control, it has a headphone connection, volume control from computer, and built-in battery (to supplement the USB power)...Could be a one box stop for you...
Netbook to USB DAC to Headphone Amp on Batteries
Are there any good DACs that I can use with a laptop or netbook, which are either USB powered, battery powered, or rechargeable for at least a few hours?
I am very happy with my Lenovo netbook for traveling, and have a spare 6 cell battery which means I can work and/or listen to music for most of the flight to London.
My Grado headphone amp travels easily and runs for hours on 9 volt batteries.
So all I need now is a good DAC?
Would the HRT Streamer or Musical Fidelity VDAC work this way?
Thanks for any ideas.