This was posted 3 days ago, but I'm a bit behind in checking all the posts in this thread. I just wanted to comment because I'd wondered the same thing about some of the slightly negative comments posted by people immediately after receiving the X5. I'd wondered if the X5 simply needed burn-in time. IMO, the answer is yes. The player sounded quite ordinary when I played it & checked in on the sound over the first few hours. So I put the player on a loop of the music I use for burn-in and just let the X5 run for at least 24 hours. I'd check in every once in awhile & to my ears the sound definitely improved after about 10 hours or so. Not sure of the exact time & not sure if it continued improving after that. But to my ears the music sounded fuller and detailed after a good burn-in period. I have a few songs that I know the sound of & I always test any new audio device using these tracks that I know to evaluate the overall sound.
And I am loving the X5's sound. It is really, really good. It is almost as good as my desktop setup with an audiophile-grade DAC. And I've been using Westone 4 IEMs with them because they're the best sounding IEMs I have & the X5 sounds great with them. I haven't bothered with an external amp yet because the X5 is plenty loud for me and the quality of the opamps in the X5 is good enough that I don't expect any noticeable improvement with the use of my latest favorite amp, the FIIO E12DIY. It really sounds like FIIO learned from the X3, as well as their amp experience, and used that knowledge to their advantage in creating a gorgeous sounding DAP.
BTW, I'd asked in an earlier post about the X5's OTG function, but I've answered my question myself since I received it. The OTG function works really well with the X5. I'm impressed with how securely the included OTG cable fits in the USB slot. It can be a real pain with the DX50, for example, if the OTG cable gets jostled because it easily loses its connection & it's like the drive has been disconnected & then reconnected. No such problem with the X5. I've hooked up various flash drives using FIIO's cable, using drives all the way up to 256gb. So that's a LOT of easily portable storage for the X5. (It also makes it easy to swap my music around to different DAP's). The only drawbacks to using an OTG drive is that I can't charge the X5 while using OTG, and since the OTG drive draws power form the X5, the play time is somewhat decreased. That's where it would be nice if the player had a separate AC adapter... but I know I'm in the minority with this... I'm just thrilled to have the OTG function added to the already superior storage of 2 micro SD cards.
Great job, FIIO. What an awesome DAP for $350.
Same to me but i love the sound before burn-in. I found it have better detail