http://www.wifihifi.ca/LatestNewsHeadlines/Hands-OnReview:AudioQuestDragonFlyBlack1.5/Red.html
Bypass the crap quality 25-cent internal DAC and introduce an external DAC or micro-DAC (preferred) as follows
(1) Apple lightning to USB3 camera adapter from the MAC Pro or iPhone 9-pin lightning port to the microDAC.
(2) plug in the External DAC or microDAC to the USB input in (1) above :
suggestion : Audioquest Dragonfly microDAC ..... Highly recommended
FWIW ...I did a lengthy personal A-B bake-off audition with the Red and new Black, and I actually preferred the Black as an overall performer . It is highly likely to be a bespoke headphone dependent result for you.
(my mobile headphones: Master & Dynamic MH-30’s.)
(3) Just plug the 3.5 mm connector plug on the headphone cable into the microDAC 3.5 mm connector plug , and you are good to go.