Great Review Brooko, I may have to "Borrow" your ideas of listing what you look for in a device for my review as well, helps establish what you looked for and why XD

Thanks & no problem.  I also seem to have started the trend of making sure disclaimers are posted (ie whether you're reviewing a sample or something you've paid for), and also posting some background on your own preferences.  Both (IMO) are essential for readers to get the most out of a review & I'm pleased to see people using them.  Any improvements I can assist with, others are more than welcome to use

I've been adding disclaimers for as long as I've done reviews, don't want people to get the wrong idea, But after you and @nmatheis did your review I decided to add an about me section. Not as in depth, but I wanted to give some background!

Many thanks for this interesting review. Having been very frustrated with the UI of my X5 and the stupid thumb wheel for ever as I stroll through 2 x 128Gb cards worth of music the X7 seems a better bet for finding what you want to play.
 When you use the internal Fiio app I presume this uses the full Fiio audiophile circuitry and when you use the android aspect it introduces the android limitations to the audio conversion.
 The sensible storage and proper UI are what I have been looking for. 
 will wait as the firmware improves

@Oldvalvemic - one thing which helped me with the original X5 was sorting folders into alphabetic groups /A-C, D-F, G-I etc - then artist, then album.  it really helps if you are an album at a time listener. The X7 UI is like a breath of fresh air though.  I really loved it - miss it now that it's on tour though.

im a new member and great review , i was wondering if anybody can can give me advice on upgrading, i m currently running an x5 gen 1 with a e12 mont blanc ,,,, would it be worth upgrading to replace both units?????? purely on a sound quality perspective????  i mainly use akg k702 headphones ....thanks for any response.

For now, hang onto your existing set-up.  The X7 with IEM module won't run the K702 (I used to own that too).  There are new amp modules being released soon and when they begin to appear, we'll have a better idea of performance.  Of course you could go X7 + E12, but that would be a pretty heavy stack. 

thanks for replying so quickly ....and i will prob take your advice , save myself a few hundred quid see how it all develops for now ....although x7 plus e12 ....would it be a big jump in audio quality ???? and happy new year too you. 

I haven't heard the E12 - so can't really comment. If anything it would just give you more options on headphones you can pair.  Personally I didn't find much difference between the headphone out and line-out of the X7.  Both were excellent

thanks again ....read your review on fiio x7 a few times and decided to order one yesterday ...will run it through the e12a mont blanc to run the akg 702 when at home until more powerfull amp mod released ....know its off thread but just read your review of dunnu dn2000j ...they sound great! and thinking of purchasing ......thaanks for info and great reviews.

Brooko, thanks again for the excellent write-up.  These types of reviews are invaluable.  You mention in the original post that you were listening to your entire music collection in 256aac which I'm currently doing with my 128gb iPhone 6s Plus (83GB).  Have you been able to compare the two?  The DAC on the iPhone is supposed to be pretty good, so I wonder if you can tell any difference between the two (major or minor).  Thanks again.

@majo123 - if you want to use the X7 in a desktop situation - especially after the DAC is unlocked - definitely look out for the K5.  Should have some info on that in a review shortly.
 
@saintintn - thanks, I appreciate the feedback.  Yes there is a noticeable difference.  The DAC in my iPhone 5S is pretty good IMO, I've always rated Apple's products - they do know good sound. But the X7 is a class above.  It has a quality that is really hard to describe - I think I called it holographic a few times before. There is a better sense of space and separation, and something about it that just pulls you in. It's the same sort of thing I've heard on Luxury & Precision's LP5 Gold.  You're playing an album, and you just don't want to stop.  The differences for me are not night/day type - but still there.  I'm hoping to get the tour unit back in a couple of weeks, and when it gets here, I'll buy it off Fiio if they let me.

Did you ever turn off the blue "pulsar light". I found it made a pretty big difference to battery (according the the android battery screen, it was the #1 power drain)

I'll try it if I get the review unit back for a follow up. It is still out on tour at the moment.

Wow, that is such a complete and detailed review! Thanks a lot, its very impressive  

Thanks Nik.
 
Jeremy - I got the unit back, and yes, turning off the pulsar light seems to have helped.

I just purchased mine!!!  I will be getting it next week!!!

Thanks @Brooko for your review.
I have a question though, how did you test the sound signature difference b/w other Fiio DAPs?
Was it blind-test with switchbox, with 0.2s maximum switch time, or simply "impressions/hands-on" test with manually connecting HP to one, then to the other?

I volume matched each DAP first - and then I had to manually switch - so it was just an A/B test.  Like I said in the review - completely subjective, but as "objective" as I can make it.  I don't have a switch box - but even if I did, the only way to be completely objective would be to have someone helping me so it was actually blind.  For the purposes of this review, I'm not making any claims, just simply stating my subjective impressions.  How the reader interprets them is over to them.