To adjust the volume of Your Network Player, Digital Pre-amp Mode needs to be enabled within your unit's settings.
This feature will then apply to the analogue outputs of the unit only. This is because the amplification occurs after the DAC within the unit's circuitry.
To enable Digital Pre-amp Mode on your Network Player please navigate to Settings > Audio > Digital Pre-amp Mode.
Once enabled, you will be able to control the volume of the unit and in turn, your entire system via the control knob on the front of the unit, the remote control or the StreamMagic app.
Please note, that the muting function of your mobile device may also mute the Network Player.