Currently running my HD6XX at between 12 and 1 o'clock on the A5 at high gain. Granted, it's brand new, but I am hearing the difference between the cans being amped and un-amped.

can this drive dt990 600 ohm version?

Benn - it handles the 600 ohm T1 with no issues - so should be fine with the DT990s

ok thank you for replying brooko

@Brooko. I primarily would be using my Sennheiser Hd-700's.

Very interesting review. It's a shame you didn't already have a (Fiio E12) to compare the SQ, Imaging, etc... as obviously I wouldn't be planning to buy simply basing on specs because as someone already stated, no human can already hear 0.003% so it's not 0.001% that would make any difference. I feel like the main difference could be the Muse Opamp but then would it simply be different or better?

I already have the E12 + X5ii combo, really love the new 3.5mm cable from the A5, it looks cheaper but is much smaller. The price of the A5 is really decent imo at only 180$CAD but I wouldn't want to swap 4x25¢ for 1$ if you see what I mean so what do you guys think about this and for how much could I sell mmy E12? I use the (Beyerdynamic T90 250Ohm) headphone and never any EQ or Bass Boost features.

@DLR Group - the HD700 is a pretty easy load to drive (I used to own a pair). The A5 will have no problems with power delivery.

@PanzerIV - I don't see why you'd swap the E12 for A5 unless there was something you did not like about the E12. From what I've read it is a great amp.

@Brooko - Yeah I know it sounds silly but since I haven't been able to compare side-by-side, I can't know if it's just gonna be swapping 4x25¢ for 1$ or if there is a small improvement. Anything less than at least something "small and noticeable" would of course not be worth it unless I'd be selling first my E12 for enough to cover most of the A5's charge. I was mostly curious about the Muse02 Opamp which seems to have a very high reputation about being prolly the clearest and overall best opamp on the market and I remember one of the first company to use them was Asus with a desktop DAC/Amp they released a few years ago for juste way too much and they add a special edition with those opamps costing like twice the regular version.

Anyhow, I'm not only wondering if going from the E12 to the A5 would be worth the hassle, but more if I would get better sound quality with a desktop amp instead such as those below, or if the A5/E12 are actualy just as good as those desktop amps below as if it is then I would much rather keep what I have as it would be more versatile by serving 2 purpose (Computer & Fiio X5). 

- www.massdrop.com/buy/little-dot-mkii-tube-headphone-amp
- Objective 2 Amp
- Fiio K5 Amp

If you're running a lot of the time from PC - then I really would recommend the K5.  Oodles of power and very linear.  But the A5 is definitely a good amp - just expect it to be overkill with IEMs.  I guess only you will be able to tell from a feature POV which one will suit you best (ease of use docking for PC vs the versatility of portable).
 
Do you know anyone in Canada who you could borrow from for a side-by-side?

@Brooko Unfortunately there isn't a single damn ******* local store in Canada or at least Quebec province, that has Fiio product in stock ready to try. There is only 1 place I know and they don't hold all of them, and most often just the cheaper models. That's what I hate about high-end stuff, it's a lot more expensive and you often can't get to try it first before buying.

I've checked the K5 and I don't really see how it is any better than the A5.
- It's not as recent.
- Doesn't have Muse Opamp.
- The A5 has a THD of 0.002% and a SNR of 115dB, so the K5 would be inferior already spec-wise.
THD<0.01% (1 kHz)Signal-to-Noise Ratio (SNR)=110dB (A-weight) [AUX IN]- It is more expensive and bigger.
- I would never use the docking capability, neither the DAC feature of my X5 II as the point is to use the much better (2500$CAD) DAC of my computer (NAD M51) before going RCA>1/8 to an amp to my (Beyerdynamic T90) headphone.
- It would also require an extra power connector to go on my fully used power surge, yet it wouldn't offer cleaner power/sound to the amp versus the A5.
 
So yea, unless it has something magical that I've totaly missed, nothing from it seems to be better. I also never use IEM earphones and would have plenty of battery already with the A5 which I can charge anywhere at any time, and I like the fact it would serve 2 purpose rather than 1, therefore reducing the cost by 2x since I wouldn't have to buy an extra amp just for the computer alone if it would perform either the same or a little less :/

Thank you for a great comprehensive review! Now to a question to you guys here in the comments: I want to buy something to help my iPod touch with it's sound quality. Should I go for an A5 (that honestly seems like a great device) or should I go for something that also houses a DAC (e.g. a FiiO E18)?

@Panos T That really depends on your headphone and what you plan to do in the futur. Remember that getting stuff seperately is always better than having a "2 in 1" device. Just think about it, if the E18 can fit inside both a DAC and an AMP, don't you think it's AMP section is gonna be as good as the A5? Definitely not.

If you had a better DAP (Digital Audio Player) such as the Fiio X3 2ndGen or X5 V2 like I have, then I would say it's internal DAC is already good enough so it would be like swapping 4x25¢ for 1$, and having just an external amp would be better but now you have an Apple product which is very meh imo. The last one I had was the (iPod Classic 80Gb) long ago and since I had a Fiio product I never looked back, even my Cowon S9 32Gb was largely better. Do you have 250-300Ohm headphone, something hard to drive, do you listen mostly to Flac files or MP3 with VBR0 or 320Kbps CBR or less quality files? You need to give us more info if you want a better answer.

Right. It's in the middle of the night over here so didn't think that far... Sadly as I've already curated my music collection on Spotify for way too long to make a switch to something else comfortably right now I'm stuck with 320kbps MP3s as my best option. On the other hand the headphones I use while out and about are pretty easy to drive (Aiaiai TMA-2s with S04 drivers) so that's a good thing. I'd really prefer keeping my setup as mobile as possible so I'm okay with sacrificing some quality to get a compact solution. Any more info needed?

It's confusing for the (TMA-2) there is too many choice on the website for the same model, plus different drivers, just What? Anyhow if it is just small 40mm drivers at 32Ohm, then you wouldn't really need an amp in my opinion. I have 50mm 250Ohm drivers, I MUST have an amp for my (Beyerdynamic T90). Considering your headphone and the iPod that's much worse than a Fiio X3/X5, I'd definitely recommend to go with the E18 over the A5.

Panzer's right - unless you're planning on driving something pretty difficult in terms of power, then an amp isn't going to net a lot of gain.  Your other issue is whether or not you can actually use the DAC on the E18 (you haven't said what model iPod you're using).  If you're going to be looking at an all-in-one with plenty of power, and good features, with a lot of storage potential - I'd really recommend the X5ii (and with X5iii released now they are going pretty cheap).  If you don't need the extra storage, the X3ii is also great value.  If you need connectivity (bluetooth/wireless), and don't mind spending a bit more - then the X5iii.

Thanks for the help this far! I'm playing music on the latest gen iPod touch and I'm currently not planning on replacing it with any other type of music player. I should be able to use the DAC by connecting through the lightning port, shouldn't I? 

@Panos T Ya you should be able to do it through the charging port at the bottom. When I had my (iPod Classic 80Gb) I would use that Line-Out to go from a large iPod connector to a 3.5mm then directly to a cheap portable amp. It says in the description of the E18 that you can connect it to an iPhone/iPod so you won't have any problem.

@Brooko I just received yesterday evening my new (Fiio A5) from Amazon.ca and wow I love it so much already. Paired on my T90 250Ohm it is the perfect match as I have just enough power while staying in low gain, with the maximum "8 o'clock?" being a little too loud, unless the recording has been done on low volume with zero loudness on purpose for higher dynamic which is super rare anyway, then it could still be just loud enough for half the people at maximum volume but it's preferable to then switch in high gain which gives +13dB and then don't go past 2 o'clock.

So the E12 just had too much power for nothing, and I'd much rather sacrifice that as I can still very easily blow my ears off on high gain with the A5, but rather get the improved clarity and soundstage. Since the specs of the E12 were already very good, I doubt it is the slighty improved SNR and THD that did the difference audible to my ears instantly. It's probably much more because of the Muse02 Opamp. I got used to my E12 but I could tell right away that the treble "higher freq" were less agressive/fatiguing when I tested on death metal or "female screaming". I also felt the bass extension were improved. Many said the E12 felt kind of narrow, well that's definitely true as I did find it a little wider on the A5.

Overall definitely worth the upgrade as anyway I'm gonna sell my E12 used for 120$CAD and I paid the A5 brand new 170$CAD + Taxes so not like if it would cost an arm. I highly doubt anything under 400$ or even 500$ can get much better than this, it's such a good price/quality ratio and the specs of the A5 are already better than the Objective2 desktop amp from what I've seen this night so guess I should just use it for both mobile/desktop rather than waste money on buying another amp that would be pricier, bigger and no better.

@Panos T - you are talking about using the E17K right?  The A5 has no DAC.  If you need a reasobly priced lightning to micro USB cable, this one from Penon works well with my iPhone - http://penonaudio.com/L19-Lightning-to-Micro-USB
 
@PanzerIV - glad you liked it as much as I do  Sounds like a great deal, and agree as a portable powerhouse there is nothing else I've tried which I would recommend over the A5 for power, portability and price.

Yeah, I'm considering an E17K or E18 for mobile. I've read some good things about the Oppo HA-2SE too but it's so much more expensive here in Europe so I think I'll go with one of the FiiO models instead. Thanks for the cable suggestion, I'll check it out!