I have it on stereo mode. The MS matrix is off and I set the monitor mode on. I tried two headphones, one being an iPhone and the other a Sony one. Both has no sound coming out, however if i slowly turn the headphone 3.5mm it gives me a tiny sound of my playback audio, very low though! I have used a zoom h4n before and never had this problem, even using a iphone headphones i was able to monitor audio. Do you think the device is defective? Again, I dragged files onto macbook and it plays wonderfully :/