Re-edited and condensed from my Denafrips Iris review, I breakdown why you may (or may not) want a digital-to-digital converter (DDC).
Link to manufacturer's webpage
https://www.denafrips.com/iris
Link to my Patreon
https://www.patreon.com/abritishaudiophile
Link to Denafrips Pontus II review
https://www.youtube.com/watch?v=NA9GD7arBlw
Time stamps
Intro 0:00
Galvanic isolation 1:18
Optical isolation 2:09
What is I2S? 2:48
Sony/Philips digital interface 3:37
USB asynchronous connection 4:55
I2S: The quality of the clock 6:04
Types of crystal oscillator 7:23