FOSTEX HP-A3 32bit DAC FOSTEX Headphone Amplifier Built-in 32bit D/A Converter, High-Resolution Audio Compatible You can listen to audio sources from optical digital or USB with headphones. Power and headphone connection have been tested and confirmed to work. Upon close inspection, there are some minor scratches, but overall it's in good condition for a used item. It seems to pair well with HD650 and K701 headphones.