Audio Note Meishu Phono - Manual (Page 8)

FRONT
Inspect a 300B valve base and you will notice that two of the pins are larger than the
other two; this is to help ensure that the valve can only be inserted one way.
The larger pins must face each other when each valve is inserted into the appropriate
valve base on the central board.
With gentle but firm pressure insert the valve into its socket. Check again that both
valves are fully inserted correctly in to their respective valve sockets.
Looking from the front of the amplifier, insert the
5U4G valve into the last empty
socket located on the right, situated between two smaller valves. Locate the rib on
the central pin of the valve and align with the valve base (it can only be inserted one
way due to this locating rib) and with gentle but firm pressure insert the valve.
Check once again that all valves are correctly fitted, and then replace the top
cover.
VALVE INSTALLATION Continued…