lol, just because you can connect it directly to a headphone does not mean you should. A line out for it's intended purpose is suppose to hook up to an external amp. Sure its signal is clean as it should be but it's not recommended to directly drive even sensitive headphones.
It may sound nice and you may like it but most sensitive phones have low impedance and the line out has a huge impedance value which surely is affecting the frequency response of these phone. So the sound you are hearing is completely different from what it is suppose to be. Especially on the bass region.
The main reason you want to hook it up in with an external amp is because DX50 implemented the volume control in the DAC. For optimal SQ you have to turn up the volume all the way up and let the amp attenuate the volume going to your headphone so as not to damage your hearing.
So yeah you can connect a headphone directly to the line out. But you should not do that.
I don't use the Line Out, i actually like the HO, but a lot of people throughout the topic has claimed that the Line Out helped with hissing and gave a blacker backround, that's why i said it. I'm using 10 ohm headphones through the HO and i have no hissing issues whatsoever. Considering the line out on the DX50 doesn't actually work like a regular Line out, it is a viable option, since it wouldn't be the same as to use a pair of headphones straight to a USB DAC. Anyway, just saying what's been said in the topic.
It's not defective. If you move to 1.2.6, it's using a different scanning technique and to get it to work right requires few simple steps. I suggest you go back to prior posts to find out how. In conclusion, you might need to delete the .audio_data folder on the sd card in order to allow a full, lengthy I might add for the 1st time, scan.
Good luck but please don't give up. I went back and forth with 1.2.5 and 1.2.6 and prefer the scanning progress bar on the latest release. At least you know it's working and where you are and when it's over.
I'd also add, you might want to delete the album art in the DX50 internal memory. I had some issues with the cover art when i deleted the .audio_data folder for a re-scan, and didn't recognized any of the covers in it (despite the fact that previous to the scan, most of the albums had art). After i deleted both folders, the scan picked up the cover art and my whole library again.