Fosi Audio BOX X2 User Manual page 6

Note:
Once 3.5mm AUX plug in ,the MM input will automatically
interrupted, so the input mode will turn to 3.5mm AUX
input.
Input priority: 3.5MM AUX input > MM turntable input.
Step 4:
Connect the power adapter to BOX X2 and the socket.
Turn the Multi-function Knob ( Power Switch/Gain
Adjustment Switch) clockwise for one time to power on
the BOX X2.
Note1:
The power adapter does not have a power indicator light,
so connecting to the socket means power is on.
Note2: Before connecting the power supply, please make sure
that the BOX X2 is in "OFF" position when connecting to
the power adapter. Otherwise there is a "POP" click
sound from your speakers.
When the connection is completed, please turn on the BOX X2
first, then turn on the amplifier (or powered speakers), at last turn
on your turntable or other audio source, then enjoy.
Note: If you turn on the amplifier (or powered speakers)
first, then turn on the BOX X2, there is a "POP"
click sound from your speakers, it is normal that all
the phono preamp have the same issues, please
don't worry about it, the "POP" click sound will not
damage your amplifiers or speakers.