Depending on the design and quality of the DAC/system connections, USB directly out of a Core ROCK/Nucleus to the DAC can be “noisy” for some listeners, especially if the power isn’t isolated and/or grounded properly. This is why people have different experiences and argue over the importance of linear power supplies.
This is being debated on this thread: Nucleus straight to DAC vs Nucleus to Streaming Transport (Endpoint) to DAC
As I stated in that thread, and will clarify here: Don’t let these details confuse and/or frustrate you. Both applications can sound great when executed properly. It’s best to start simple and tweak as your system, and your ego, desires.