Onkyo TX-NR 838 Manual page 31

Windows 8, click "Play to", and then select this unit.
5. Adjust the volume using the volume bar on the "Play to" window.
Sometimes, the volume displayed on the remote playback window may
differ from that appeared on the display of the unit.
When the volume is adjusted from the unit, the value is not reflected in
the "Play to" window.
This unit cannot play music files remotely in the following conditions.
– It is using a network service.
– It is playing a music file on a USB storage device.
– "Agree" was not selected in the "DISCLAIMER" screen that was
displayed when the NET input was selected on the unit for the first
time.