Nyquist hands audio to the system route
On iPhone and iPad, AirPlay appears in the system route picker. On Mac, Nyquist uses its selected CoreAudio device for direct output; AirPlay routing is chosen from macOS Control Center. In both cases the operating system participates in preparing and transporting the network audio.
Source rate does not guarantee output rate
A source may be FLAC at 24-bit/192 kHz, but that does not mean every AirPlay destination receives those same properties. Protocol version, sender behavior, receiver support, grouping, and downstream processing can introduce format or sample-rate limits. Nyquist therefore does not promise unchanged source-rate delivery over AirPlay.
AirPlay and UPnP/DLNA are different paths
For a compatible UPnP/DLNA receiver, Nyquist sends the original file without transcoding and the receiver opens that file. AirPlay is a system audio route rather than original-file delivery from Nyquist. A receiver can still process either path after it accepts the audio.
What the signal path can say
Nyquist can identify that a system route is active and show the source properties available to the app. It should not extend macOS USB DAC status, exclusive mode, or DSD over PCM claims to an AirPlay route. Where the operating system does not expose the final transport details, the honest state is device-dependent.
Choose by the job
AirPlay is useful for system-integrated wireless playback and multiroom destinations. A directly connected USB DAC offers more device-level control on macOS. Original-file UPnP/DLNA delivery is useful when a receiver supports the library's containers and codecs. These are different transport designs, not a single quality ladder.
Related: the audio signal path, Bluetooth vs. USB audio, and Nyquist output behavior.