If you have an iPhone and you care about its audio quality there are some DAC dongles, see also
https://www.whathifi.com/advice/how-to-play-hi-res-music-you...
Quoting the article:
"Next, you need a decent DAC such as the Audioquest DragonFly Cobalt, Cyrus soundKey or Chord Mojo 2 and a good pair of headphones, such as the Grado SR325x, Shure Aonic 3 or Austrian Audio Hi-X55.
This is just a starting point, of course. Don’t be afraid to build up to a more revealing system. You could combine the Chord Hugo 2 DAC with a pair of Beyerdynamic T1 (3rd Generation) headphones for a more premium set-up. That might be a touch overkill and punishingly transparent for an iPhone, but these are hi-res files, after all."