One thing to note is when you are charging the unit (from power source and not from connecting to a PC).
The battery icon at the upper right shows some movement changing from empty to 1/3 to 2/3 to full in rotation.
However, it does not tell me how many percent full so until it is fully charged, I will not know how much is charged.
Yes, I can unplug it to check the battery how full it is but not possible while charging.
Hopefully this will get improved in the next firmware update.

@ridhuankim - it's the same way on all the Fiio DAPs.  Normally I just allow 4 hours from empty, about 2 hours from 1/2 full.  And all I do is check the LED on the power button - if it's red, it's still charging.  if it's green, it's finished

Thanks Paul! That's explain! I didn't check T1 impedance curve. So higher voltage power supply is essential for T1. Thanks!

+100 excellent review.
Wish all other reviewers were that careful & serious about their comparisons and generally about those elusive SQ impressions

Great, honest review.  I own both the X5 and X5 II and find the latter easier to listen to for long periods than its forerunner. 

I couldnt have asked for a better review than this.Infact Fiio X5 (secondG) was just about available here in India and I was looking for a suitable review which could help me to decide in spending approx $350.
Even though I am not an expert in the technicalities about digital audio, but love to listen to music and was looking for a suitable player to add on to my OPPO HA1 and HD 800 !
I did order one and is expecting by 30 June .
cheers

I couldnt have asked for a better review than this.Infact Fiio X5 (secondG) was just about available here in India and I was looking for a suitable review which could help me to decide in spending approx $350.
Even though I am not an expert in the technicalities about digital audio, but love to listen to music and was looking for a suitable player to add on to my OPPO HA1 and HD 800 !
I did order one and is expecting by 30 June .
cheers

Thanks again gents
@Umeshdhingra - let me know what you think of it when you get it. HD800 may need a little more amping than the X5ii can supply by itself - but it will be interesting.  Congrats on your purchase and I hope you enjoy it

I basically plan to use Fiio X5 as a media player by connecting with OPPO HA1 / HD 800, but when not at home , then use my HD 598 with Fiio X5 both as a media and DAC.
will write in more detail once I have had my hands onto X5.

Ok - sounds like a really nice set-up. Look toward to hearing what you think of the Fiio in due course

Nice & thorough review.
 
I received my X5 Gen 2 (adding to my X5 Gen 1) and can report the OTG is a PROBLEM (where my X5 Gen 1 handles OTG perfectly).
 
This is what I reported to FiiO:
 
Hi Team FiiO,
 
I just received my X5 2nd gen and I'm disappointed as it isn't handling OTG storage as my X5 first gen does; it fails to provide an essential feature.
 
While my 128gb microsdxc exFat cards from my X5 1st gen work fine, my FiiO OTG cable from the original X5 with a Lexar 256GB thumb drive does not.
 
I get a message "External USB STORAGE removed" that reappears continually after I dismiss it. Furthermore, the new X5 doesn't mount/read the OTG storage. Please note that my X5 generation with fw2.5 handles this external OTG storage perfectly.
 
Please advise as this decrease in functionality is unacceptable.

@mshmovie - thanks, but I clearly stated above that I couldn't test OTG (I don't have a cable). There are at least 2 people who have it working in the main X5ii thread - so maybe see what is different in their set-up?

I've read this three times now. (once on Headphonia) I really dig the way you are able to compare all the other Fiio units. I have the X3ii and love it. I've been using it with my tube amp and on the go. I've personally decided to wait for the X7, if I can hold out that long, but I'll be perfectly satisfied with the X3 while I wait.  Thanks for a great read.

Thanks KC.  I'm also intrigued with the X7.  Hopefully I'll get a chance to review it when it comes out.  The X3ii still remains my most used daily DAP.

@Brooko Thanks - I did read that you didn't test OTG (and read everything you wrote with great appreciation). I just expect the X5.2 to be at least all the X5.1 was with regards to OTG (and more). I briefly had it working for a few minutes today, then back it reverted to the "External USB Storage Removed" message. Fingers crossed on FiiO's response to the reported issue.

Very good, comprehensive review.

Wow, another standard setting review.

@Brooko Can you comments on differences in the sound signature/quality between the Micro iDSD and the X5ii as a DAC? I have the iDSD for my home desktop use, and I am thinking about getting the x5ii for portable and office desktop use. Thanks!

Thanks guys - I appreciate the comments.
 
@aerosuffly - it is kind of difficult to compare the two as it's not just the DAC you're comparing - but DAC and amp section in each device..  Anyway I set the two up, and volume matched - but it still takes a bit of time to switch, so this is really subjective. I used the AKG K553 as it is relatively easy to drive. They are actually pretty close - even in tonality.  Both have a very clear and almost vibrant sound. The X5ii seems just a touch warmer, the iDSD just a touch more space and a little leaner.  Both sound pretty good though - and the similarities are there tonally. At times during the switching it was easy to forget which one was actually playing.  I'd think having the X5ii for an iDSD substitute while you're traveling would be a pretty good option  If you want something even smaller - check out the Cozoy Aegis at some time (I'm reviewing it currently).

@Brooko Thanks for a quick response. That sounds very convincing, so I ordered the X5ii today.
 
I see your point about the mingling of the DAC and the amp sections. I actually use the iDSD with the iCan (and the iUSB), which tremendously improve the sound (to my taste). The amp section in the X5ii should be more than sufficient to drive my IEM (ATH-CK100Pro), and I can always add an external amp to the X5ii for my office use. I will see how it works.