How do I set up the Master Volume feature so one device always controls the volume?

Hold SETUP until the red indicator stays on, release, then press the device button for the device you want to control the volume. Press and release MUTE, then press and release VOL+. The red indicator will blink twice and turn off to confirm the setting. You can test it by switching to another device mode and checking if the designated device's volume still responds. (Page 11)