The DR-40 has two xlr inputs, but you are plugging a single source into it.
If you want to record the sound from the microphone onto both channels, you’ll need an XLR “Y” cable which would have one XLR Female end to go into the mic, and that splits out to two XLR Male connectors to plug into the L and R inputs of the DR40.
All you are doing, however, is recording the same thing to both tracks, which isn’t really giving you any benefit.
Personally, I would advise plugging the Mic into the Left XLR Input. Press the REC MODE button on the front panel to open that menu. Change the Rec Mode to “MONO” and set the source to EXT.
By doing this, you’ll be recording a single track file, which is all you really need (plus, it will save space on the card, so you can record about twice as much audio compared to recording in Stereo).
when you go to edit your footage, just pan that track to the center position if you want to hear it in both speakers.
Michael Paul
Location Sound Corp