Q: Can DAC s power headphones?

A: Some DACs have circuits on their output side that can run most headphones without issues -- for example the Benchmark DAC1 is a reference DAC that also has a high current, low impedance headphone amp. Now you can use it as a DAC with fixed output to a standalone amp, but in reality you could use it as the only equipment you will ever need, if you wanted to. The HPA2 on the DAC1 is very capable of powering 2 headphones on its dual outputs, including most higher impedance headphones. The volume knob allows you to easily adjust the level of the output, and so you can set your source volume at 100% and use the DAC1 to pretty much manage your entire personal audio experience.

In contrast, you have the Schiit Modi, which outputs a line-level signal via the RCA jacks on the back. The Modi output may not be powerful enough to power many headphones, and you have no way of adjusting output volume unless you modify the source level (which is typically not the best thing to do since the sound quality can degrade).

So the trick, if you want a single unit solution, is to find a DAC/amp combo, or a DAC that has a headphone amplifier circuit built in. Keep in mind that some lower-end DACs don't really splurge on the quality of the built-in headphone amp since they don't see the need (many of their customers will be using standalone amps anyway).