Disclaimer: I am not affiliated to Fiio in any way and do not benefit monetarily or in any other form for writing this review. I purchased this in-ear monitor with my own resources and I am simply giving my honest review of the product!


Review by: “Charlie” from The Little Audiophile


Fiio. A company that has really made a name for themselves in the audio industry. Their X-series of DAPs has been making big waves in the audio world for their high quality players that does not cost a kidney and a liver. Fiio’s A-series of Amplifiers are again, known for their excellent price to performance ratio. Today I will review the Fiio A3, which is the company’s mid range portable headphone amplifier. With the MSRP of just under S$90, this amp delivers, just without the massive price tag.


FEATURES



The Fiio A3 features a 1,400mAh battery, rated for 16 hours, a Low and High gain setting and a nice Bass Boost function. It has a very low output impedance of <0.2 ohms and Fiio recommends pairing the Amp with headphones with impedance ranging from 16-150 ohms. I know… these are all just numbers and specs where you can read online. But I’ll explain more on these features throughout the course of the review.





AUDIO QUALITY


Right. Firstly, lets talk about audio colouration when using this Amp. Luckily, the Fiio A3 is mostly neutral and transparent throughout the frequency range when Bass Boost is turned off. Which is good because an Amplifier’s main purpose is to deliver more power to the headphones and not modify the sound signature in any negative way.


Music sounds richer and more immersive even, when I use the Fiio A3 with Bass Boost on. The music seems to be more intimate, while soundstage on certain headphones, seem to expand. It is honestly hard to put in words what I am hearing. It is like tasting fresh milk when you have been drinking low fat milk all along, and now you don’t wanna go back. It is something like that…


Anyways, the Bass Boost function gives aoughly a 4dB increment in approximately the mid-bass region at 50Hz which as mentioned, helps in making the experience more immersive. It is good to note that this increase in bass does not muffle the mids, which in turn means that vocals remain clear even though the bass is emphasized. However with Bass Boost on, sound stage seems to narrow down a little.


Now, the A3 definitely isn’t the end game in the headphone amplifier market. It too has it’s downsides and to be fair, I’ll have to talk about the not-so-good parts of the Fiio A3. Here goes.


Bassy headphones suffer from very mild Static like/Distortion(y) sound in the low bass to low mid-bass region when Bass Boost is on and when listening on average volume with the dial turned to 6 and my source at 50% volume. I first noticed this when listening on my Massdrop x Nuforce EDC where the low and low mid-bass(es) sometimes sounded unstable and there was a little bit of growling-like noises.


The A3 does sometimes exhibit very soft static noises in between changing tracks that does not affect the music when it plays, but I think it is a good thing to note.


One last boo-boo about the A3 is channel imbalance on low volumes. When the dial is set under 2, the left channel is obviously louder than the right channel. However in it’s defense, I never actually listen on such low volumes anyway. With low gain, my volume dial is usually set within 5 to 7, depending on the track, ambient noise and headphone used. At such settings, the channels seem balanced enough.




USER EXPERIENCE


As important as sound quality is, the user friendliness should not be forgone, such that the user would even bother using them. These are my thoughts on what I liked and disliked about this amplifier.


First off, I really liked the Analog dial that the A3 uses. It allows for a better control over listening volume.


Secondly, Fiio decided that changing the issued 6 rubber feet to 2 white translucent rubber pads is more feasible. This I wholeheartedly agree, considering that the Fiio A3 is a portable amplifier, and would be stacked with a phone, DAP or perhaps even a DAC most often. It prevents scratching of it’s “other half” and makes stacking so much easier.


Thirdly, I had wished for different coloured indicator lights to . Perhaps blinking red for charging, steady green for charged, steady blue for normal operation and steady red for errors instead of slow blinking, rapid blinking and steady blue for its status indicator.
Lastly, I had wished that Fiio used a 1/4 inch jack for output instead of a 3.5mm jack, just like the one that the iFi iCan Nano sports. It would open up that many more options as for headphone pairing. However with the compactness of the Fiio A3, a larger jack might not be possible and I might just be being nit-picky here.





CONCLUSION


I believe that the Fiio A3 is an excellent performer for its price range and comes with a limited, but well thought out set of accessories.




I have personally tried the Fiio A5 which comes in at a significantly higher price at $199 at the point of writing this review but I could not hear any significant improvements in sound over the A3 despite it’s better specifications. The iFi iCan Nano is another amplifier that I had the chance to audition, and yes, they definitely trump the Fiio A3 slightly in terms of audio clarity, but do bear in mind that the iCan Nano comes in at S$259, which is nearly three times the cost of the A3! I love the iCan Nano’s performance but I personally and most certainly cannot justify the price. It is without doubt good. But not like three times as good. I always keep this mentality before I make a purchase, that is “specs are just specs. In practice things are different. And that is what is most important.” For the average user or even the audio enthusiast, the A3 is very user friendly, extremely compact and very well built and it sounds awesome! The power output is adequate for most headphones up to 200 ohms to get to a decent listening level.


The Fiio A3 pairs very well with my Astell and Kern AK Jr and does really help liven up the bass region in my music. In closing, I believe the Fiio A3 might be the amplifier for you if you are looking for an amplifier with a excellent price to performance ratio and do not wish to bottleneck your “mid-fi” audio equipment.



Do check out our WordPress site at https://thelittleaudiophile.wordpress.com/ for more reviews!

INTRODUCTION

When I first came to Head-Fi I was naturally curious about portable amps. When I got my first one (the old E7) I was blown away – the increase in clarity, details, soundstage! Then over time, as I read more, experimented more, and (more importantly) tested more, I can to realise that those benefits I was sure I heard, had mostly come about by simply turning the volume up.  And with the portable amps I was using, I wasn’t volume matching when comparing.  Once I actually started comparing objectively, most of the time those differences disappeared. Sure – there are times when you absolutely need an amp – like with the 320 ohm VE Zens, or if I want to drive my HD600s portable, and there isn’t enough volume. But for a long time with my portable listening, I stopped carrying a portable amp.
 
Then around Sept/Oct 2014, I worked with Fiio to set up a “Down Under tour” for their new X1 DAP, and as a bonus they also threw in their E11K amp. At the completion of the tour, I offered to buy both units from Fiio (and yes – I paid real money for them), and the last 12 months has given me a whole new perspective on portable amping, why you might want to use one, and why the budget prices E11K (A3) portable amp from Fiio should be considered.
 
ABOUT FIIO
 
By now, most Head-Fi members should know about the Fiio Electronics Company.  If you don’t, here’s a very short summary.
 
Fiio was first founded in 2007.  Their first offerings were some extremely low cost portable amplifiers – which were sometimes critiqued by some seasoned Head-Fiers as being low budget “toys”.  But Fiio has spent a lot of time with the community here, and continued to listen to their potential buyers, adopt our ideas, and grow their product range.  Today, their range includes DAPs, portable amps, portable dac/amps, desktop dac/amps, earphones, cables and other accessories.
 
Fiio’s products have followed a very simple formula since 2007 – affordable, stylish, well built, functional, measuring well, and most importantly sounding good.
 
DISCLAIMER
 
The E11K (A3) portable amplifier that I’m reviewing today was purchased by me (direct from Fiio) at the end of the Australasian tour I organised.  I have no obligation to write this review, I am not affiliated to Fiio in any way, and this is my honest opinion of the E11K (A3).
 
PREAMBLE - 'ABOUT ME'.
(This is to give any readers a baseline for interpreting the review).
 
I'm a 48 year old music lover.  I don't say audiophile – I just love my music.  Over the last couple of years, I have slowly changed from cheaper listening set-ups to my current set-up.  I vary my listening from portables (Fiio X5ii, X3ii, LP5 and iPhone 5S) to my desk-top's set-up (PC > USB > iFi iDSD).  I also use a portable set-up at work – either X5ii/X3ii > HP, or PC > E17K > HP.  My main full sized headphones at the time of writing are the Beyer T1, Sennheiser HD600, and AKG K553.  Most of my portable listening is done with IEMs, and lately it has mainly been with the Dunu DN-2000J, Jays q-Jays and Alclair Curve2. A full list of the gear I have owned (past and present is listed in my Head-Fi profile).
 
I have very eclectic music tastes listening to a variety from classical/opera and jazz, to grunge and general rock.   I listen to a lot of blues, jazz, folk music, classic rock, indie and alternative rock.  I am particularly fond of female vocals.  I generally tend toward cans that are relatively neutral/balanced, but I do have a fondness for clarity, and suspect I might have slight ‘treble-head’ preferences.  I am not treble sensitive (at all), and in the past have really enjoyed headphones like the K701, SR325i, and of course the T1 and DT880.
 
I have extensively tested myself (abx) and I find aac256 or higher to be completely transparent.  I do use exclusively redbook 16/44.1 if space is not an issue.  All of my music is legally purchased (mostly CD – the rest FLAC purchased on-line).
 
I tend to be sceptical about audiophile ‘claims’, don’t generally believe in burn-in, have never heard a difference with different cables, and would rather test myself blind on perceived differences.  I am not a ‘golden eared listener’.  I suffer from mild tinnitus, and at 48, my hearing is less than perfect.
 
For the actual listening part of this review I used the E11K (A3) mainly with my X3ii or X1 DAP, and a little bit with the iPhone 5S. Observations about the E11k (A3) are taken from the past year I’ve owned it. This is a purely subjective review - my gear, my ears, and my experience.  Please take it all with a grain of salt - especially if it does not match your own experience.
 
FURTHER NOTES
 

1. Although Fiio are in the process of rebranding/renaming their portable amp line from E series to A series, from this point I’m going it simply call it the E11K.  It’s just easier.
2. Volume matching was done with a calibrated SPL meter and test tones (1 kHz) when required for comparison.
3. Frequency response and distortion measurements were taken using a relatively cheap Startech USB soundcard (which measures pretty well – 0.012% THD and 0.024% THD+N – which was consistent at 300 Hz, 1 kHz and 6 kHz @ -3 dB volume as suggested by ARTA using loopback). I combined this with a licensed copy of the ARTA measuring suite. The soundcard has a calibration adjustment applied – so that it measures dead flat from 20 Hz to 20 kHz.

 
WHAT I LOOK FOR (NOW) IN A PORTABLE AMP
 
I thought I’d list (before I start with the review) what I would now look for in a portable amp. This is useful to remember when looking at my reasoning for scoring later in the review.

1. Genuine portability
2. Good battery life
3. Clean, neutral signature
4. Easy to use
5. Low output impedance
6. Reasonable output power – should be able to drive IEMs and earphones up to 300 ohms
7. Good gain control
8. Value for money

 
PORTABLE AMPS I’VE OWNED IN THE PAST
 

1. Fiio E7, E11, GoVibe Porta Tube, Headstage Arrow 12HE 4G, Beyerdynamic A200p
2. Current portable amps E11K, E17K, VE Runabout

 

THE REVIEW

PACKAGING AND ACCESSORIES
 
The E11K arrived in Fiio’s retail packaging – a white, red and black box measuring 130 x 130 x 25mm. The front had a picture of the E11K, and the rear has some specs and other information in English and Chinese.
 
 
Opening the outer retail box reveals an inner box with a foam cut-out (securely holding the E11K), and a secondary box for the accessories.  The accessories include:
 

1. 6 stick-on feet
2. 1 x 3.5-3.5 mm cable (Fiio’s L8 mini to mini)
3. 2 rubber stacking bands
4. A USB to mini-USB recharging cable
5. Warranty and instructions

 

 
The entire package is practical, covering everything you initially need for the E11K.  Materials are all good quality. If there was one thing I’d change it would be ditching the silicone feet (they slide around on the body) and instead including one of their silicone stacking pads.
 

 
TECHNICAL SPECIFICATIONS
 
The table below lists most of the relevant specifications for the E11K.
 
BUILD / DESIGN
 
The E11K is rectangular shaped with slightly bevelled edges, and a slightly curved top side and under side. The main body is a solid machined block of aluminium. At one end is the Alps potentiometer – nicely nestled between two raised protective arms (so it’s more difficult to accidentally bump the pot), the high/low gain switch, and the on/off bass boost.
 
 

At the other end is the 3.5mm headphone out jack – still nice and firm after a year’s use, a blue LED (solid blue when on, flashing blue when charging), a micro USB charging port, and the line-in 3.5mm port. Overall the external build is really solid, and even after a year my unit has very few scratches or bumps. The curved surface feels good in the hand, but it is the one design error I think Fiio made with this amp. It’s simply not that well suited for stacking (and that is what a portable amp will be mainly used for after all). If you’re using other Fiio gear with it, then their stacking kits and silicone pads really help – but the curved surface wasn’t one of Fiio’s smartest choices in this case.
 

 
Opening the unit up, it’s easy to see the curved one piece body, and also how compact and tidy the layout is. One thing I also noticed was that the underside is fitted with a shroud.  I guess this has two possible uses – as a guard against accidental static flashes from the board – but maybe also as an EMI shield.  Compared with the older E11 (which I used to own), I have had no problems with EMI (and with the old E11 this could be an issue).
Some may find it a bit strange that the ports are at the opposite end to the volume pot – but I actually (over time) have found it quite natural. The good thing about this configuration is that the volume pot, bass boost and gain switches are very easy to get at (no cables getting in the way).
 

 
 
 

HEAT AND POWER
 
So far I’ve noticed no heat build-up at all with the E11K.  Even after a couple of hours (driving my HD600s), it’s still cool to touch.
 
For output power the E11K uses the OPA1642 for preamp and the AD8397 as its power amplifier. Fiio rates the target headphone impedance as 16-150 ohm, and I think that maybe a lot of people see this and automatically assume this little unit can’t drive a headphone like the HD600 (300 ohm properly).
 
But as I do the final edit of this review, I’m sitting with the X3ii feeding the E11K, then into my HD600’s.  Volume on the pot is around 3/9 (low gain), and I’m getting a very comfortable 65-75 dB with minimal effort.  This is my usual listening level so I’m pretty content. Taking the HD600 off my head, and cranking to maximum volume gives me 90 dB peaks.  High gain would add another 15 dB to take that to 105 dB – more than you’d ever need.  And at no stage do the HD600 feel under driven.
 
 

With a variety of headphones / earphones at my disposal, the test track “Sultans of Swing” by Dire Straits, and X3ii feeding E11K via line-out at low gain – these are the approx. volume settings to get to a comfortable listening level (for me) at around 70-75 dB on low gain:
 

1. HD600 (300 ohm, 97 dB SPL) = ~ 3-3.5/9
2. VE Zen earbuds (320 ohm, 106 dB SPL) = ~ 2.5-3/9
3. Trinity Delta IEMs (16 ohm, 110 dB SPL) = ~ 2/9
4. Dunu Titan1 IEMs (16 ohm, 90 dB SPL) = 2-2.5/9
5. AKG K553 Pro (32 ohm, 114 dB SPL) = 2.5-3/9
6. Dunu DN-2000J (8 ohm, 102 dB SPL) = 2/9

 
And for giggles because I can

1. Beyerdynamic T1 (600 ohm, 102 dB SPL = ~ 4/9 (Not recommended though – sounds a little thin)

 
So you can see that the E11K has a heap of power on tap – far more than its recommended 16-150 ohm headphone range belies. Clearly Fiio are being safe with their recommendations. Even switching to my lower output iPhone 5S (at full volume emulating a line-out) into the E11K, and again pairing the HD600s, the E11K only needed a slight bump to around 4/p on the pot.
 
FEATURES / USEABILITY
 
The E11K couldn’t be much simpler to learn to use.  Simply plug your source into one socket, headphones into the other, press play on the source, and adjust the volume on the pot of the E11K to suit. The E11K has a really low output impedance (<0.2 ohm) so it should suit even the most sensitive earphones.
 
 
It does come with a bass boost (on/off) which I’ve measured as lifting the entire volume by about 1 dB, then lifting the bass between about 30-200 Hz with the main peak at 60-80 Hz – around 3.5 additional dB. It is noticeable but subtle (which I rather like). There is also a gain switch which raises the overall volume by ~ 15.5 dB.  The thing I like about this is that it a decent change in gain, and actually makes a difference – rather than just being put there as an afterthought.  Unsurprisingly, I really don’t use the gain toggle at all – unless it’s a low powered source, and a hard to drive load.  Nice to know it is there though.

 
 

Another feature which has been added from the original E11 is that this time you can charge the E11K and still listen at the same time.  Nice for those moments when battery is almost gone, you’re close to a power-point, and you still want to be listening. The other thing I really like about the E11K is simply having a proper pot to use.  It’s really nice being able to get to an ideal listening level with a very quick tweak of your fingers.  I’ve noticed virtually no imbalance either – even getting to the bottom of the pot.
 
BATTERY LIFE
 
Fiio rates the play time on a full charge at around 16 hours, recharge at around 4 hours, and for my use I’d suggest that time is pretty accurate. What I really like about the E11K though – and probably the reason I use both it and the E17K so often now – is that using it with the Fiio X1 or X3ii line-out extends battery life on both Fiios by at least 5 or so hours.  So if I was going to be on a long haul, or somewhere I simply needed extra life with my DAP, one of the two amps always comes with me.
 
SONICS AND PERFORMANCE
 
I’m going to preface this section with a little critique I received a while ago (by PM), and my answer to it – so that you can understand why I don’t comment on some things, and why I do comment on others.  I was told my review on another amp was poor because I didn’t include sections on bass, mid-range, treble, sound-stage, imaging etc – yet referred to an amp as warm, full, or lean.
 
Now I can understand the reference to warm / full / lean – as they are very subjective terms, and whilst I’d like to avoid their use, they are invaluable to convey true meaning. Comparing my NFB-12 to the Aune X1S for example – the Audio-gd does sound richer and warmer.  It’s the nature of the DAC which is used.
 
But I choose not to comment on bass, mids, treble, and most definitely not sound-stage – simply because when we are talking about an amp – they shouldn’t be discussed.  An amp’s job is to amplify the signal with as low distortion as possible, and output as linear signal as possible.  If it is doing its job properly, there is no effect on bass, mids, or treble. And IME an amp does not affect soundstage (unless there is DSP or crossfeed in play) – that is solely the realm of the transducers and the actual recording.
 
So we have that out of the way how does the E11K perform sonically?
 

 
The first thing I did was to check the linearity of the E11K, check its bass boost and its gain.  To do this I used a calibrated sound card (calibrated to measure completely flat), ARTA and a loopback. In the low gain and high gain frequency tests the E11K measured flat – amazingly flat. So what you are getting is an amazingly neutral amplification not adding or taking away anything. Channel balance throughout was also very good - approx than 0.3dB and for me that meant completely unnoticeable. The graph above is a close-up.
 
Next up was distortion measurements.  My USB soundcard measures (on loopback) THD at 0.010%-0.013% and THD+N at 0.020%-0.032% at pretty much -100 dB (this was with separate readings at 300 Hz, 1 kHz and 6 kHz).  When I added the E11K – I got exactly the same measurements with it in loopback – so the E11K is measuring lower than my USB sound card can measure.  It also means that the distortion and harmonic distortion are both inaudible. Fiio states measured THD at 0.004% on their lab equipment, and I have no reason at all to doubt this figure.
 
 

The last thing I measured was IMD, and again this was below the threshold of audibility, and again the E11K was measuring below the actual thresh-hold of the USB sound card. So what does this tell us?  Simply that the E11K supplies very linear, and very clean output.  Purely subjectively, it sounds very neutral – no added warmth or brightness I can discern.
 

 
COMPARISONS
 
Because I don’t have a lot of other amplifiers at my disposal, I simply used what I had available – the VE Runabout, and the Fiio E17K.
 

 
E11K (USD $60) vs VE Runabout (USD $100)
The VE runabout is VE’s first portable amplifier (from the same company that brought us the excellent Zen earbuds).  It is battery powered (9v battery), and at 235g and dimensions of 110x70x25mm, it is quite literally 3 times the size of the E11K.  It also measures below the distortion floor of my sound-card, and measures completely flat in frequency response.  It has a gain switch (only ~ +4-5 dB), and no bass boost. Battery life is incredible – it seems to go forever (I haven’t measured it yet – but will do so when I review it). According to VE it will put 150 mW into 32 ohms, which actually puts it behind the E11K on output power – but again it has driven my HD600 with absolutely no issues. In a volume matched blind-test, I can’t tell the E11K and Runabout apart – both sound excellent – clean and clear. But in a head-to-head comparison, the little Fiio beats it handily on size, portability, weight, form factor, features, and value.
 
E11K (USD $60) vs E17K (USD $130)
The E17K is a DAC/amp. It has an inbuilt battery (15 hour rating) and digital volume control instead of analog. At 110g and 104x62x13mm, it is marginally larger than the E11K – but the difference is mainly in length. It has 3 levels of gain 0dB, 6dB and 12dB, and has a tone toggle (-10 to +10 bass, and same on the treble).  Again it measures below the distortion floor of my sound-card, and measures flat in frequency. Its output is 200mw into 32 ohms (a little less than the E11K) and again has no issues driving my 300 ohm Sennheiser HD600s. Again in a volume matched blind-test, I would have difficulty picking the E11K from E17K.  The E17K does however have a very good DAC, tone controls, balance, and other inputs and outputs, and is incredible value at $130.
 
If I only needed an amplifier, and had no need of the other features the E17K provides, the choice of the E11K is an easy one to make.  However, if you like having the additional features, and have use for the dac function, then the E17K may represent better value.
 

E11K VALUE & CONCLUSION

I’ve now had the E11K for a year, and although I didn’t use the unit a lot in my early days with it, over the last 6 months, I have come to use it more and more. If you are using Fiio DAPs like the X1 or X3ii, I can thoroughly recommend the stacking kit too.
 
The E11K brings very good size, weight, power, and sonics together in an extremely budget friendly package. In fact, I cannot think of a better amp to recommend to someone just starting out in audio, and I think ultimately even seasoned audio lovers may really like what Fiio has brought to the table with this mini dynamo. In fact for a beginning audiophile, one of the best value for money combos you could get would be an X1 + E11K + stacker kit IMO.
 
Going back to my original list – I can say it has ticked every one of my boxes my boxes for portability, ease of use, output power, battery life, sonics, impedance, and gain.  If there were two minor things I would like to see changed it would be to see a two stage gain (maybe make the first at around -6dB, then at +3 dB and +12 dB.  This would give more usable play on the pot (fine tuning). And also I’d like to see the form factor return to a flat body– so that it is easier to stack (although with Fiio’s stacking kits this is less of a problem).
 
All in all, I would recommend the E11K to both audio starters and the more experienced without question.  For what it delivers, it is incredible value for money. 

First off, let me say now that I am not an audiophile. I am a fan of audiophiles though and I learn a lot from you guys. I'm more of a budget-audio-enthusiast and I'd like to keep it that way. Some parts of this review will be to re-affirm some of the observations with this product and probably add some recommendations for the benefit of our budget-conscious members like myself. So let's begin, shall we?

Update --> I purchased the latest version (2017) since I sold the first one some time ago. I am now pairing it with my smartphone (Lenovo K4 Note). See where it says (Update) below for some updates on the latest release version.

PACKAGING (Update)

The latest packaging of the A3 (2017) has the following items:

• 2 Hi-Res stickers, on the packaging and the unit itself.
• 1 Ultra-short interconnect, as with the Fiio A5 (replacing the usual 3-inch ic)
• 2 Rubber pads (replacing the rubber feet)
• I'm stacking this with my phone so it's temporarily attached to my clear phone case with a reusable adhesive (sturdy but easy to remove Elmer's Tak 'N Stik). This does not damage the unit's surface at all.

REASON FOR BUYING

I always wondered if my headphones, the JVC HA-RX700, would benefit from a portable amp so I decided to dig some reviews and possibly find a good match. The most popular budget choice is the Fiio E6 so that was my first choice. Fortunately, there is a local store that lets me audition those first so I got to listen before deciding. First, it turned out that my headphones did benefit from the amp. There is some change in the sound quality, most notably in terms of clarity and bass but not necessarily in the sound stage. Not that I'm not content with how my headphones sound. They already sound great but I'm looking for that extra energy, especially in the treble and bass department. The E6 did that to some extent but EQ1 (red) is a little bit overbearing and the bass response is not that clean and muddied the mid-range a little bit. EQ2 (blue) sounded much cleaner but this time it lacked the bass energy I was looking for. I did not really pay too much attention to EQ3 (purple) and EQoff so I can't comment much on those. To cut the story short, the E6 is great for its price but I'm looking for more. So I stepped up the game, auditioned the E11K and the rest, as they say, is history. That history is actually written below.

BUILD AND DESIGN

The build is superb. It has this feeling of indestructibility to it. The brand new unit's switches are tight and sturdy. The volume meter is smooth but not loose. I'm sure that it will last for years unless you intentionally or accidentally damage it. It feels like it can really take a considerable beating.

Design wise, it looks gorgeous. The brushed aluminum makes it look like a premiere gear. I know that some may prefer the line-in and out ports to be at the front of the unit, together with the volume meter but this design works for me. I have it strapped to my smartphone (Samsung Galaxy Mega 5.8 l9152), which has the headphone-out port at the top-end so I had the bottom-end of the amp facing that area then I plug in the interconnect and headphones from there quite easily. I just reach underneath my phone for the volume meter to adjust it ever so slightly then it's good to go. The power indicator being at the bottom-end also helps with my set-up. Again, it depends on where your headphone-out is. I'm pretty sure you'll find your way through it.

SOUND

It added just the right bass energy I was looking for. It's not overwhelming but it's not lacking at all. It's really powerful and clean and it did not bleed out at all to any of the other frequency ranges.

It added a significant amount of treble energy. The highs (e.g. cymbal crashes and hits) are clearer and more prominent. Mid-range is also noticeably clearer.

Sound stage is about the same but more centered and balanced. It gives this concert hall effect, especially with songs that involved some orchestrated arrangements (e.g. Queen's Who Wants To Live Forever). Stereo imaging is unaffected though this is somewhat expected.

Overall, the sound is fuller and richer with a lot more energy. More importantly, I would say it's mostly neutral. My headphones' sound signature is maintained, with just the added prominence where I need them to be (bass and treble). So to my JVC HA-RX700 friends who are still wondering if those headphones sound "good" with an amp, they don't. They sound "great"! And they go perfect with the E11K.

CONS (Update)

1. Channel imbalance until level 2 in the volume dial - I did not really find this disturbing and this has been explained by Fiio quite clearly - http://fiio.me/forum.php?mod=viewthread&tid=40050. (Update) It's still there, but less noticeable on the latest version (2017).

2. Slight static when music is paused - At first, I was disturbed by this but this turned out to be normal for low impedance and highly sensitive headphones. I tested this behavior against the store's test unit and the result is the same. What helps though is:

a) If you're using a portable source which is not very powerful (like a smartphone), set the source volume to max then control the volume from the amp. This worked for me and static is no longer there after pausing as long as I stay within acceptable (not too loud) listening levels but results may vary as you switch to a more powerful source. I believe the logic is that the signal from the source must be as strong as possible to avoid static/distortion. Again, please test what works best with your set up.
b) Switch to Low Gain. Your low impedance or highly sensitive headphones will likely handle the low gain volume setting more easily. In analogy, it's biting the right amount of food and it can chew it just easily. This is the safest bet. A quick notice though: High gain for me sounded more forward and open and bass is just a little more prominent. I listened to it enough to spot the difference. Low gain sounds "tighter" (not in a bad way) and a bit (a very tiny bit) more detailed but I like the high gain sound better. Again, it's a matter of preference. Just adjust that volume ever so slightly to avoid hearing damage.

(Update) When music is paused, it's silent (version 2017). This is a significant improvement from the earlier releases. There is still EMI when stacked with a phone but pausing music, I can not detect any noise, even with more sensitive IEMs like the KZ ZS3.

3. Phone interference - And yes, it's not perfectly shielded and you will hear the "tut tut tut" if a call or a text message is coming in or if the phone is picking up a strong signal but I think this is normal. It doesn't happen often and I believe it won't be a problem if you're not using a phone as a source so don't sweat it. Overall, it's still decently shielded in my opinion.


BATTERY LIFE

It takes about 4 hours to full charge. Keep a close watch if you're nearing the 4-hour mark. Upon full charge, unplug the unit as it heats up a little if not done so. I believe the unit has a built-in protection for overcharging but just to be on the safe side, unplug it at once when fully charged.

The published usability at full charge is more than 16 hours and I can attest to that. I believe rechargeable batteries improve after several charging cycles so I'm counting on it. If not, I'm pretty much content with about 16 hours of usage until next charge.


FINAL THOUGHTS

Fiio's published product page says, "great layering and medium and high frequency extension" and "with great control of low frequencies and smooth drive". I couldn't agree more. I'd highly recommend this product for its purpose.

For the budget enthusiast, if you can push your budget a little bit higher, go for the E11K instead of the E6. If you can audition both, you'll hear the difference, I promise. Don't get me wrong, E6 is decent but E11K is more than decent. It's on a league of its own. I even read reviews that it can compete with its higher priced big brothers but I'm not qualified to comment on that. I did not have the chance to try those. Just know that with the Kilimanjaro 2, your getting best value and sound at a reasonable price.

(Update) I believe overall that version 2017 is a better value in terms of accessories set and the improved noise floor. I can't imagine it to improve anymore but it actually did. Great job, Fiio! This remains to be your best value amp a few years after its release.