Article Index
FiiO X7
p3 Sound Quality
p4 Conclusion
p5 Measured Performance
All Pages

The X Factor



Top of FiiO’s portable digital player range is the new X7 that uses Android as an operating

system and offers a host of capabilities. Noel Keywood gets to grip with its complexities.


Portable audio is a global market so large it can support investment in high technology and FiiO are leveraging this to gain advantage with their new X7 high-resolution digital player. It’s a technology showcase, aimed at Astell&Kern players that have lead the market by technical prowess and great sound quality for some years now. But as Astell&Kern’s prices have risen substantially, a gap has opened up for others to exploit – and FiiO have done so most effectively. The X7 is top of FiiO’s range, but at £500 it is priced little differently to the AK100, at the bottom of Astell&Kern’s range. 

All of which is to get this player into market context. In case you’re new to the breed, the X7’s basic role is to drive headphones, but it can also drive a hi-fi system, delivering sound quality better than CD – something I look at closely with portables. In this case the picture is a bit more complicated than usual: at a functional level the X7 best integrates through a docking station, the K5 costing £96, and this needs to be considered as part of the package, although it is not essential as I will explain.



This top view shows the Line/Coax (digital) 3.5mm four pole  output jack.

The left side has volume, on/off buttons and a microSD card slot.


FiiO say the player uses top-quality audio parts that consume high current, so it needed to be fairly chunky – and it is – to house a large 3500mAh re-chargeable battery, with a claimed battery life of 10 hours. Measuring 130mm high, 64mm wide and 17mm deep the X7 is pocketable, if a bit much for a shirt pocket. Its chassis is machined from a block of aluminium and it feels like it – strong and impressively rigid. Aluminium may be light, but a weight of 208gms registered on our scales all the same – quite substantial. This puts it well above FiiO’s other models, such as the 165gm X5, but below other fully spec’d hi-fi players like Lotoo’s PAW Gold at 280gms, reviewed in our October 2015 issue.




The bottom of the player with an AM1 module attached. It carries the

headphone output and microUSB connector that meets the OTG (OnTheGo) standard.


FiiO’s stated weight for the X7 is 220gms, higher than our measured weight, but that’s because the review sample came with a standard ‘low power’ (as they put it) AM1 bolt-on module, designed for in-ear headphones. There are, in addition, medium and high-power modules, as well as a balanced output module, but little info is available on them and when I contacted the factory for details they were away for the CNY, they said (Chinese New Year). The modules are secured by two tiny Torx screws; a screwdriver and spare screws are supplied.

Where players I have reviewed over the years seemed to gain outputs as their price rose, the X7 with AM1 goes back to basics. There is one headphone output in the AM1 module, a standard 3.5mm stereo jack at the bottom of the player, a slightly awkward place to be. The top face carries the only other output, a switched Line/Coax socket, Coax meaning an electrical digital connection in this case, not a co-axial optical output within a 3.5mm headphone socket, as used by Apple and Astell&Kern. 





The Pure Music mode play window shows album artwork, graphic equaliser, favourites ... and more.


FiiO supply a special adaptor cable with four-pole jack to phono line socket so a standard digital coax S/PDIF connecting cable can be used. You can’t use this socket for headphones because Line has no volume control: when switched to Line it is a fixed output suitable for the CD input of a hi-fi amplifier, using a 3.5mm stereo jack to Phono adaptor lead, not supplied.


In addition to these two sockets a microUSB carries power and mates either with the K5 docking station or connects to a computer through a microUSB-to-USB A cable so music files can be uploaded; it is seen as a mass storage device. Our X7 could not be used as a DAC; FiiO said on their website at time of review that this would be made available in firmware FW1.8, but after upgrading our sample to FW1.8 there was no sign of it, either in the menus as a selectable option, or as an available Output on a Mac (running OS-X 10.11.3, El Capitan).



The track listing screen in Pure Music mode carries artwork thumbnails.


As FiiO’s top player, you can be assured that the X7 plays all digital audio file formats, normal and double rate DSD (but not quad) in .dsf and .dff file formats, as well as .iso (SACD) files. 

FiiO say the player will in a future firmware upgrade also support DoP through its digital output so DSD can be sent to an external DAC like Mojo. Mojo offers better performance, measurement shows, so this is a potential upgrade. All Apple file formats are supported, WAV and FLAC of course, DXD and all the old compressed formats.  

The X7 runs on Android, unlike their other players, and this complicates its user interface by introducing two basic modes: Android and Pure Music mode. I ran in the latter, but had to switch to the former to go online etc; a re-boot is needed – not exactly convenient. 




The graphic equaliser has a range of preset modes, plus a user adjujstable mode.

It shows response in a graph.


The player has wi-fi that, FiiO say, facilitates auto-updating, but in our early sample player this did not work and it had to be manually updated. 

The Pure Music mode interface was usable but needed clarification by use of colour in Settings category headlines, for example; its monochromatic nature was neither attractive nor helpful. 

FiiO provide few sound options, Low or High gain (meaning output), Gapless playback, Line/Coax. A 10 band equaliser is available, but only during track play; it has eight presets and a user definable mode. Info/option screens can be slid in from bottom, left and top, with a finger swipe. 

Storage comprises 32GB of on-board memory, that contains Android OS support files, plus a music files folder. You only see the latter in Pure Music mode; you see them all when uploading via USB from a computer. Additionally, there is one microSD card slot that will address 128GB maximum; a card is not supplied.

Like Astell&Kern players, but unlike FiiO’s less expensive players, the X7 has a touch screen, eliminating the rotating selector and offering more screen area. Overall, however, I did not find the X7 easier to understand or use. I am no fan of gratuitous complexity and Android moves the X7 toward a mobile phone-type user interface, with lots of bells and whistles – and my pockets and home already have plenty of these, with clocks, apps., accelerometers, web browsers etc. popping up all over. I may be in a minority here by not being wowed by this stuff – and it is why I like the straightforward simplicity of FiiO’s less grandiose players.



The Settings menu is poorly delineated by same-colour category headers.



The touch screen controls are duplicated on the right side by a transport control and there’s a volume control at left, comprising Up/Down buttons. Start up is a not so fast at 28 seconds, from what FiiO proudly describe as a Rockchip RK3188 CPU. However, more interesting because of its direct relevance to sound quality, was their use of an ES9018S DAC chip in the X7, from the renowned Sabre32 series produced by ESS of California. With four of its eight channels paralleled per stereo side this offers, potentially, 123dB Dynamic range, and most manufacturers (e.g. Audiolab) achieve 120-122dB our measurements show. 

However, in conjunction with an OPA1612 acting as current-to-voltage convertor, and one as a low pass filter, plus OPA1612 feeding an AD8397 headphone driver in the AM1 module, FiiO achieve 117dB dynamic range from the X7 our measurements showed, 5dB below what is possible. All the same, as portables go, this is a good performance – ignoring the 125dB achieved by Chord’s Mojo. 

I must quickly mention that our review sample had early FW1.0 firmware and it would not update automatically over wi-fi from FiiO’s website, as claimed, nor would it update manually from a file downloaded onto a Mac (OSX 10.11.3). Macs automatically unbundle zip files so FW1.8 had to be re-compressed, but still no joy. In the past hidden Mac desktop files were the cause of this problem but these days Mac-zipped files usually run. The X7 only updated from a PC (Windows 7) download, I found, saved straight to the X7’s root directory, so Mac owners are going to have problems unless FiiO either sort this out, or warn of the issue on their website/instructions.



The K5 dock is a small desktop unit 120mm wide and 130mm deep, not including protruding plugs etc. The X7 simply plugs in on top, connecting through its small microUSB OTG connector. This is usually a 5pin serial digital link but as the rear digital inputs are simply pass-throughs to allow file loading from a computer, it seems that X7 connects to K5 through an analogue link within microUSB, not digitally. There is no DAC in the K5 it seems, hence no independent digital input as such: the digital inputs are pass throughs to the player. 


FiiO's K5 dock has a small, plastic flip-up door on top that covers the docking connector

when not in use. Front switches select input and gain.


This link feeds a Texas Instruments TPA 6120 A2 headphone drive chip and it gives quite different results to the X7’s AD8397, delivering a massive 7.7V output maximum to headphones through the large 1/4in stereo headphone socket on the front panel – more than enough to drive any headphones; the big knob at front is a volume control. 

At rear are two 3.5mm stereo jack sockets, carrying Left and Right balanced outputs intended for the balanced (XLR) inputs of stereo amplifiers. There are also analogue inputs and outputs. 

FiiO say K5 has an internal power supply but it does not, coming with an external switch-mode delivering 15V at 1.5A – and unidentified as ‘FiiO’ or ‘K5’ by a sticker, so its identity and purpose will be lost amongst all the other under a desk if it becomes disconnected. The dock charges the X7. 




The X7 running solo as a portable – not docked in other words – was full-bodied and almost mild-mannered in its delivery, it was so creamy smooth across the midband. 

The 9018S lacks glare and shout, and this came across playing Rock. The drum synth in Queen’s 'Radio GaGa' (24/96) was seemingly mighty in its power, if a little soft in leading-edge definition. Queen’s harmonies stretched wide though, out far left and right. In true ESS fashion I could hear right into the vocals – this is a very revealing DAC. Treble was finely detailed too, forming a rich tapestry at the high end of the audio scale, and this was delightful. 



The K5's rear carries balanced outputs through three-pole 3.5mm jack sockets,

rather than XLR sockets. There are digital pass-through inputs and connector for

an external power supply, as well as Line inputs/outputs.


Unfortunately, when the screen timed out to save battery power, volume became locked, so I found myself constantly stabbing the On button for revival to access volume; setting screen sleep to its maximum of 30 minutes alleviated the issue, but volume should be accessible with the screen off. 

Playing through a wide variety of Rock I found the AM1 module mild-mannered and full-bodied, lacking the speed and punch of my Astell&Kern AK120 and far off a Chord Mojo DAC in terms of scale and definition – temporal and spatial.

However, the FiiO is optimised for in-ear monitors - which tend to be more explicit - as Jon Myles found with his Noble K10s it proved very lively (see box-out for more details).

Moving on to Classical, and with 'Saturn' from The Planets I was treated to a lovely peaceful background behind the orchestra as slow kettle drum strikes and horns increased in intensity towards a climax; the X7 sounded magisterial in this role. 

On the K5 dock the X7 gained both speed and bite in its timing, sounding altogether larger bodied and less somnambulent. There was less of the smooth creamy-ness I heard from AM1 alone but drums gained size and impact, and bass lines suddenly formed a solid backing against which other band members could work. Kettle drum strikes in 'Saturn' now shook the earpieces of my Fidelio X1 headphones – impressive stuff. 







Our review sample of the X7 was, judging by its firmware, an early unit. Even with a firmware upgrade to FW1.8 its USB DAC function was unavailable – puzzling. Since the microUSB OTG Standard had 5 pins, as per standard and not 11 as claimed, I wonder whether this had something to do with it. There are mysteries here that needing sorting out with the factory when they return from Chinese New Year.

Our X7 sounded smooth, full-bodied and sweetly detailed but pace and punch were lacking with over-ear headphones. However using good quality in-ear monitors things were markedly different and the FiiO proved a sterling performer. 

It remains to be seen whether the currently unavailable Medium Power (AM2), High Power (AM4) and Balanced (AM3) modules will have more to offer for users of different headphones.

The optional K5 dock adds scale for an extra £99 but not subtlety. 

The X7 is a complex design that tries to meet all requirements. It is for those who want a web browser, Bluetooth, VU meter apps and such like, all of which its Android operating system make possible. 


FiiO X7 player £500


FiiO K5 DOCK £96



OUTSTANDING - amongst the best. 


VALUE - keenly priced



An ambitiously designed player with complex options but fragmented user interface. Good sound for IEMs from AM1 module. 



- build quality

- big screen

- output amp options



- no USB DAC function

- no dock balanced headphone

- big

- heavy


Rhode&Schwarz UPV advanced audio analyser – used for all measurememts.


With volume at maximum, headphone output measured 1.8V, enough to go very loud with all headphones, including insensitive high quality magnetic planars. Switched to Line mode, output measured 1.4V, less than a CD player but enough to drive any line input. 

Dynamic Range (EIAJ) measured 117dB with high-resolution (24bit) digital via both headphone and Line outputs, a high value for a portable. Switching Line from analogue to digital allows an external hi-fi DAC to be used, where 120-125dB is possible with good modern designs.

Distortion was very low at 0.02%, as shown in our analysis. No distortion components are visible so ‘distortion’ here is noise, even though a narrow band harmonic-only analysis was used. 

Frequency response, with 192kHz sample rate files, reached 34kHz before a slow roll away to the 96kHz upper half-sample-rate limit.

In all, the X7 with AM1 module produced a good measured performance all round. It can drive high-quality headphones and has sufficient dynamic range to exploit the improvement offered by hi-res digital files. NK



Frequency response (-1dB)    4Hz-34kHz


Distortion (24bit)

0dB                                                 0.003%

-60dB                                                0.02%

Separation (1kHz)                         101dB

Noise (IEC A)                               -115dB

Dynamic range                             117dB

Output (headphone)                        1.8V


FREQUENCY RESPONSE (192kHz sample rate)



DISTORTION (24bit, -60dB)





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