Earlier quoted context omitted.
To be clear, unless you are in the > $2,500 headphone space, DAC quality has a hard limit of actual hearable use. Under that point, most external DACs are pure snake oil. If A user has $200 to spend on a pair of over-ear headphones. they should spend $9 on the DAC and $191 on the headphones. Hell, the $9 headphone adaptor vastly outperformed a number of $100+ DACs. The primary limitation of headphone quality onboard…
Sure, most DACs that just use off-the-shelf chips are virtually identical in terms of how they sound, until you get to the really high end, as you said. However, in practice having a cheap external DAC is a massive improvement, even if the hardware is fairly similar. I think a good chunk of it is just being able to give the software exclusive control over the DAC, and passing in the results bit-perfectly, bypassing a…
For example, the Pro/Mac Macbook Pro supports 96Khz Audio at 32 Bits according to the same built in midi tool that you would also use to adjust the bitrates of external DACs. Sure my Onyx Artist 1 - 2 supports 24 bit at 192Khz...but the external headphone jack in the latest Macs also adds a fun bonus: A built in Amp for headphones over 300 Ohms. It's a weird add, but a wonderful one. (I do dislike that it is just a resistance detector that enables it though, my Planar HifiMan headphones are just under the cut so I have to drive them with an AMP for better sound.)
Obviously, this all goes out the Window on iOS of course.