The output from the headphone jack is analog(ue) so a DAC (Digital to Analogue converter) wouldn't convert the signal, even if it accepted an analogue (line level) input, which most don't I think.
It would be best in this case to use a headphone amplifier which would connect with a simple stereo line lead: 3.5mm to 3.5 / 5mm depending on the headphone amp input.