There are already portable combined DAC&#x2F;headphone amplifier units that support lightning input (either directly or via a USB converter). I did have one for a few weeks but sent it back it as the minor difference in sound quality wasn&#x27;t worth the effort of carting it around.<p>The combined heft of both the phone and the DAC unit (most of them are similar size but twice the thickness of an iPhone) makes for an uncomfortable pocket bulge. Aside from being another thing to carry around. it&#x27;s also another thing to keep charged (like I haven&#x27;t got enough of those things in my life already).<p>Sure, the DAC on the iphone isn&#x27;t the best in the world, but it&#x27;s certainly good enough. Only when concentrating wearing studio-quality headphones in a silent room can I tell the difference between the two, and those times that I am sat in a silent room, it&#x27;s at home (which has a decent audio setup not dependent on my phone).<p>I guess there will be smaller units produced that are perhaps powered through the lightening port (if this is even possible?), but likely the sound quality produced by them will be similar to the on-board DAC&#x2F;amp circuit.