* set pulseaudio to 192kHz sample rate:
  - configuration.nix:
    hardware.pulseaudio.daemon.config = { "default-sample-rate" = 192000; };
  - or ~/.config/pulse/daemon.conf:
    default-sample-rate = 192000
* check that sound card is operating at 192kHz:
  cat /proc/asound/card0/pcm0c/sub0/hw_params