Review: Sennheiser HD-558 (modded)

Introduction

Why the Hell would I need another headphone - again? I´ve asked myself this question often enough. But I don´t have an answer. I just like to collect cans. Just as I like to change playback/recording units I love to change headphones, all depending on my current mood. Pure, decadent luxury considering other people can´t afford even one headphone. Well, I received a not-so-small amount of money as a Christmas present and decided to spend a part of it on a new pair of cans. And as the Sennheiser HD-558 had been on my Amazon Wishlist for more than three years, I finally decided that the time was right. Do I like it? Is it able to replace my dearly loved, 9-year old Sennheiser HD-600? Why don´t I just use my Sennheiser HD-448? Or my Superlux HD-668B? And what about the two headphones I reviewed before, the Sennheiser Momentum and the Skullcandy Aviator? Read on and you shall be rewarded with answers, dear constant Reader.

Design & features

Sennheiser HD-558 (with 'NOS4A' by Joe Hill abused as a headphone stand)

The Superlux HD-668B cannot be used anymore since it broke apart (only because I cleaned it!). I won´t replace it with a new unit because... well, I have grown to hate its sound. The Sennheiser Momentum & Skullcandy Aviator did many things well but suffered at others, the worst being comfort-related. In the end I decided in favor of the Sennheiser HD-558, the headphone I wanted to have in the first place. It cost me 129,- Euros, it is a plain and boring looking headphone, manufactured entirely out of plastic in China. Huh? No, I don´t have a problem that it´s been built there, it´s just that Sennheiser doesn´t like to talk about it which feels pretty double-tongued. As if they are ashamed of it. When I think of my beloved FiiO units, it's stupid and not particularly fair to the people who constantly excel at producing highly functional products for the whole world. But enough of that. This headphone is right in the middle of the HD-5x8 line. All of them are engineered to attract cost-conscious people; the HD-518 is the cheapest, costing half of what the top model, the HD-598, costs (roughly 220,- Euros). Their predecessors (HD-5x5) looked almost the same, had the same features and were - as far as I can tell - fairly successful, causing Sennheiser not to change too much. Never change a winning team, eh?

A (too?) proud German company: Sennheiser

The top model HD-598 is finished in a cream-like colour with attached faux-wood veneers, a headband with a fake leather pad and metal grilles covering the outside of the earcups. Sennheiser was obviously trying to improve the inherently bourgeois design of the predecessors; yet all they achieved was making it look tacky. The grilles of the otherwise plain HD-518 arent exactly an improvement either, they look like windows shutters. The incredibly boring and plain looking HD-558 is the one that´s honest, it´s the least flashy of all three models. When it comes to features, it´s equipped with what Sennheiser calls Eargonomic Acoustic Refinement (E.A.R.), which is supposed to 'channel audio signals directly into your ears', enabling all three HD-5x8 cans to have 'outstanding bass and vocal projection'.

Ugh, simple marketing blabla: E.A.R. is nothing more than an angled driver, many headphones are equipped with a technology where the drivers are placed slightly below and in front of your ears. Our ears' stage impression usually reacts favourably to this placement because it mimics how we listen to loudspeakers: those aren´t standing on the left and right of our ears, no, they´re standing in front of us, helping us creating a holographic image of the virtual stage. Is it a good idea to implement something like this in a headphone? Well, so far my experience tells me that it rarely works as intended... with horror I recall my second 'big' headphone, the Sony MDR-CD 570. Because most of the time it just creates colourizations - and not the desired effect of a holographic stage. But we'll see about that later.

Sennheiser HD-558, earcup: comfy velours cushions & 'surround reflector'

The diaphragms inside the drivers are a Duofol design, this principle of constructing membranes was carried over from the HD-6x0 models. They reduce distortions and improve transparency, that's what Sennheiser says. Seems to be true when I think of my HD-600; it´s the least distorting and most airy headphone I´ve ever heard. When it comes to impedance, this headphone is rated at 50 Ohms. The maximum sound pressure level (SPL) is at a very loud 112 dB, it should therefore be perfectly suited for portable units. But no, Sennheiser markets it towards music lovers, listening at home using their big HiFi system. Strange. This will become important again, so more about that later.

Accessories & built quality

Sennheiser HD-558, 3-meter cable

The box the HD-558 comes in, contains the headphone and the cable. That´s it. The 3 meter cable pictured directly above (recall for a moment that it´s targeted at at-home-listeners) comes with a proprietary 2.5 mm plug on the headphones' side. The Sennheiser site lists an additional 1.2 meter cable with 2.5 / 3.5 mm plugs suitable for portable units. However, this cable appears to be a myth as I was unable to find even one place where it was sold.

Sennheiser HD-558, proprietary 2.5 mm connector - what a dimwitted idea

In the end I had to resort to a replacement cable built by Oyaide and distributed by FiiO, the RC-HD1. This took a further 40,- Euros out of my pocket. Frankly, I find Sennheisers' brazenness of not including a shorter cable themselves, insulting. A carrying bag... are you kidding me? Not included, not offered. My cheaper HD-448 came with one, the Skullcandy Aviator had a particularly luxurious bag, the Sennheiser Momentum could be safely tucked away inside a firm, brown bag. Hell, even the super-cheap Superlux HD-668B came with a soft cloth bag. With the exception of the Momentum, all of them cost less than the HD-558 and Sennheiser cannot manage to include something as basic as this? Oh please!

Quite expensive but well built 1.2 meter replacement cable: FiiO RC-HD1

But how is it built? Despite being fashioned completely out of plastic it has been manufactured very well. Everything fits tightly, fins are nowwhere to be found, it doesn´t creak when moved or when you change the position of the earcups. The cushions are firm and they are replaceable... now, that I mentioned it: the possibility of replacing any broken part is one of the reasons why I love Sennheiser products so much. By doing so, you can extend the lifetime of their headphones. My boyfriend owns an ancient Sennheiser HD-250 linear; it´s now 26 years old. With other manufacturers you´d be hard pressed to find even one replacement part, with Sennheiser it is no problem. My boyfriend has been using the HD-250 Linear for many years for DJing, it was beaten, tortured and abused. The faux-leather cushions and the mesh covering the drivers had disintegrated completely, the cable looked like shit too... well, it was inconvenient anyway since it was equipped with a 5-pole DIN-plug! Getting new earpads (including the mesh) and a cable was as easy as ordering a new headphone with the result that this ancient thing now looks like new.

Upon deciding whether I should get the HD-558 or not, I also considered the famous Philips Fidelio X1 (gorgeous sounding headphones). At first glance, it appears to be perfectly manufactured and built to last. But any impression of reliability is destroyed once you know that its cushions and everything inside it is glued together. Even the cushions are glued to their frame, they aren´t replaceable. Perfect example of planned obsolescence if you ask me and crucial for my decision not to buy it. EDIT 17.03.2015: The successor Fidelio X2 fixes that problem. Well done, Philips!

Comfort & quirks

Velour cushions & headband: comfy and replaceable

When referring to new Sennheiser cans, people usually talk about the 'clamp of death'. It´s true: the clamping force of the HD-558 is quite strong, your head is tightly sandwiched between the two earcups. Even after wearing it almost every day for more than two months, this force hasn´t diminished. The earpad and the headband cushions are firm, but not uncomfortably so. Their one redeeming aspect is their size; while the cups of the HD-600 are even bigger, the earcups of the HD-558 are certainly big enough to accomodate almost any ear.

There´s just one thing inside perhaps posing a problem: a so-called 'surround reflector'. You see, the fabric covering the drivers is applied to a thin plastic foundation which itself protects the membrane underneath it and also forms the reflector. The latter sticks out and, for me, has been a nuisance. It causes me to re-adjust the position constantly because it tends to touch my upper earlobes. This doesn´t hurt at first but after a few hours (yes, I wear headphones that long) it starts to hurt, even when it´s only slightly brushing my earlobes. Wouldn´t be any problem at all - if the surround reflector would be softer. But the hard plastic underneath the mesh averts this. So before you buy it yourself, try it on and see if your ears fit.

The foam mod & Burn-in

Did you know that you can modify the HD-558 to almost sound like the top model of the line, the HD-598? It´s easily said and done, just look above at the video. But please, be more careful than the creator of the video, the cables soldered to the drivers are very, very fragile. They break if you blow on them. According to what people say online, by removing the piece of foam you´ll get more punch and air. I cannot attest if this is true or not, I never listened to my HD-558 before it was modded. Whatever it changes, this tweak won´t completely transform your HD-558 into the HD-598. To achieve that, you´d have to grab pliers to cut holes into the plastic structure covered by the outer felt-mesh grills. The HD-598 sports very fine metal grills which aren´t dressed up with some fabric, apparently they help to achieve a more airy sound. This might be true; before I got my HD-600 I owned its predecessor, the HD-580, which is (apart from a different colour scheme) exactly the same headphone. The only difference are the driver grills: on the HD-580 they are plastic, on the HD-600 they are metal, causing the latter to sound different. But I don´t want to remove anything that can´t be re-attached again, I´ve therefore skipped this part. Below you can see measurements by Headroom where I´ve compared the frequency response of the HD-558 against the one from the HD-598. They are extremely similar, the HD-558 emphasizes frequencies around 3,000 Hz while the HD-598 slightly accents everything above 10 kHz. The latter presumably is responsible for the HD-598's stronger amount of 'air' while the un-modded HD-558 will sound a bit more aggressive. The foam mod will bring the HD-558 much closer to the response of the HD-598, in the end you have to decide yourself of course if you actually want the sound of the top model.

Frequency response differences Sennheiser HD-558 & the top model HD-598

Whatever you decide, you simply have to burn in the HD-558 (this goes for the HD-518 & 598 too). I listened to it once I had removed the foam and in spite of it already sounding very well, burning in really brought out its strengths. I admit that I´ve never experienced ANY device reacting so strongly and positively to a burn in. My Sennheiser HD-448 remained essentially unchanged in terms of sound, the Superlux warmed up considerably but these cans turned from undifferentiated into 'differentiates-like-hell'. Spatiality improved a lot, some unpleasant high frequency sibilance was removed too. So please, burn it in. For at least 48 hours.

Tech section

Impedance response HD-598 vs. HD-558 vs. HD-448/449

I know you probably hate to read measurements of any kind. They are boring, you cannot understand them or maybe you´re simply too lazy to even want to understand them, right? Yes, in my opinion, people who ignore measurements willfully do not deserve to experience sonic bliss. So stay with me and let me lecture you, for a few minutes only, I beg you. In this case it´s important because they tell you if the HD-558 needs to be amped or not. Because the answer is YES and NO.
NO: It´s loud enough for many portable devices. At this moment I´m listening to music played back by a recently acquired Sony NW-HD5 (review will follow) and with the HD-558 it gets loud enough to shatter my ears. The same is valid for many of my portable MD recorders/players. Not to mention the FiiO E07K and the FiiO X3 (review will follow), they can kill the HD-558 with ease. Sensitivity isn´t any problem, the impedance is. YES: The HD-558 is rated having an impedance of 50 Ohms. Look above at the measured impedance response and you can clearly see that it reaches a resistance of almost 300 Ohms at 95 Hz. Meaning: a headphone output with an output resistance of more than 6 Ohm will produce severe frequency distortions.

Well suited for portable units - but not for stationary units: HD-558

Example: to monitor an MD I was recording with a Sony MDS-JE 530 (review to follow), I plugged the HD-558 into the MD-recorders' headphone socket. The resulting sound was so bass-heavy that it obscured everything else. Mids and treble were drowning in bass, it was unbearable. Beats by Dr. Dre territory? Think bigger, more blown-up and hollow. What my problem is, you ask? I´ll tell you: many big amps, CD players, network players or TVs are equipped with headphone outputs featuring a fairly high output impedance. With all of them the HD-558 will produce this bass-heavy, highly coloured and droning sound. But if all of them are playback devices for usage at home, then why was the HD-558 engineered in a way that will produce a bad sound with exactly these devices? Remember: Sennheiser targets these cans at at-home-listeners... why the fuck did they construct a headphone that will play with superior quality on half of all portable devices instead?
Thankfully I´m accustomed to amps with a low output impedance. In case I want to use it with one of my vintage portable CD players, I simply connect either the FiiO E6 or the E07K. Or I make use of the FiiO X3. Due to its fairly high sensitivity you might want to listen with it once you step outside... you'd look ridiculous though. And don´t forget that it is a very open headphone, leaking a lot of sound to the outside world. What you´re hearing, other people will hear too. So what is it for? Portable use? Electrically, yes. Isolation? Forget it. At home? Yes - but only with sources having an output impedance of less than 6 Ohms.

And now: the sound

Sennheiser HD-558: felt mesh grills

Does it sound well? Of course it does, otherwise I wouldn´t have kept it. Once it´s modded, burned in and fed by low impedance sources, you´ll be rewarded with a stage like you´ve never heard before. Only one word fits: spectactular! For decades I´ve been dreaming to hear a soundstage like this one and until the HD-558 arrived, this desire had never been fulfilled. My beloved HD-600, already featuring a realistically wide and deep stage, feels shallow in comparison. Yup, the HD-558 easily bests the HD-600 in spatiality. It´s like being able to 'see' around instruments, effects, soloists, anything. The sound is fantastically layered, not only from left to right but from the front to the rear. Every instrument, group of players, synths and effects, even reverb, is defined precisely. It doesn´t sound artificial, it feels completely organic. Very well done, Sennheiser!
The impression of virtual stage depends on the recording you´re listening too, of course. The device used for playback and amping plays an equally important role, too. For example, these cans revealed my FiiO X3 to sound a bit distant, compact and slightly constricted (I knew that before, the HD-558 only made it all the more apparent). The more recent FiiO X5 (loaned to me by FiiO, review to follow) was worse, sounding flat, confused and blurry. 'Stage kings' like the Sony MZ-R 37 or the MZ-R 55 are unmasked to sound either artificial or congested while the MZ-R 50 improved. Recordings produced using several groups of microphones profit as well, recordings with less mics will extend their dimensions. Binaural recordings... superb. It appears that the Sennheiser marketing experts haven´t promised too much when advertising the HD-558 as featuring an improved spatiality.

The fantastic stage of the HD-558 is... hard to match

Frequency response is a bit more problematic. There seems to be almost no sub-bass (below 50 or 60 Hz). Yep, deep bass is lacking badly, causing a "loose" sound signature. I´d guess 6-8 dB amplification below 60 Hz might do the trick. Frequencies above however are fully present and accounted for... which is also the reason why an impedance mismatch like the one I described above will produce a hollow and bloated sound. But when properly amped, bass is punchy when needed, dynamic and reasonably tight. Everything above low frequencies sounds balanced with a tendency towards warmth and charm. Voices have a correct chest size and won´t ever sound sibilant. Overall, I´d call the frequency response fairly leveled out from 100 to 10,000 Hz without too much colorization. My HD-448 sounds muffled against it, the Superlux... well, when it was still able to sound... no, I don´t want to compare it, it´d be insulting to the HD-558. Still, just as it would profit from more deep bass, a stronger amount of air / crispness would be benefitial as well. Sometimes it sounds rather dry; this helps differentiation and precision of course, the HD-558 will always be able to tell things apart with ease, better than the HD-600 even. But air is missing and a too dry sound appears abrasive to some people. Though 'abrasive' is the last word I´d use to describe the HD-558. But there´s no denying that the HD-600 is superior when it comes to air.

Could have more 'air': HD-558

Another area the HD-600 easily surpasses the HD-558 is the amount of details. Due to its slight warmth and missing air, the HD-558 drops tiny details. Revealing errors isn´t its forte, no, it´s a headphone concentrating on presenting music pleasantly. But don´t make the error to think that it sounds boring or that its timing sucks! Far from it, this is one of the most vibrant and snappy headphones I´ve ever heard. One minute, it´s explosive and calm the next, it sounds much more engaging than my HD-448. It can be lovely and aggressive, all depending on the recording. Will it ever sound congested, plastic-y, confused, coloured, veiled or boring? No.

Now a warning: all of this depends on how it sits on your head. The position is extremely important for the sound and no, I´m not exaggerating. Moved too far back on your head it´ll become more airy, stage will be wider but shallow, moved too far to the front it´ll sound coloured, veiled and hollow with a strange stage. This is the moment where the angled driver design rears its ugly head. All headphones more or less depend on being correctly positioned to be at their best, this is equally true for the HD-600 and the HD-448. In case of the HD-558 however the effect of a wrong sitting position is much more detrimental than I expected, to find the golden mean thus is vital for a perfect sound.

Conclusion

Put it on your head, grab a good book and dream away... crap, that was corny :)

The Sennheiser HD-558 (and when it comes to sound, the HD-598 too) is a wonderful headphone: well built, important parts are replaceable. The latter will extend lifetime of this headphone far beyond of what people are nowadays used to. It isn´t a perfectly neutral headphone, it´s a bit warmer and more charming than necessary. More air would surely improve its sound; more deep bass would too. The impedance response sucks - big time. It´ll only sound perfect with many portable devices, yet Sennheiser exclusively addresses home stereo listeners. Unwise of them to create a headphone that cannot decide which personality it´s supposed to embrace. Additionally, the bourgeois design could deter people from taking it seriously. If you can accept all that, you´ll be rewarded with a stage performance besting every other headphone I´ve ever heard (and there were many). A precisely defined rendering of objects on the virtual stage combined with a fantastic sense of space surrounding these objects... as if you would take an auditorally magnifying glass to zoom in on something without ever loosing the bigger picture. It doesn´t sound boring but vibrant and apart from the warm tilt it´s neutral enough to objectively judge sound quality should you so desire. Add to that the comfort and you'll end up with a headphone that´s wonderfully suited for hours and hours of aurally pleasure. Just use it with amps having a low output impedance, adjust the position on your head until it sounds best and you´ll be having fun for years to come. Recommended.

Pro:

• incredible stage performance; surpasses every other headphone I know
• vibrant, yet pleasant sound
• neutral from 100 to 10,000 Hz...
• ... with warm & charming character
• good differentiation
• good precision
• no distortions at all
• good timing
• loud enough with portable units
• very good built quality and haptic
• comfortable to wear for extended amounts of time
• earcups big enough for almost any earform/size
• can be modded almost to top-of-the-line model
• most parts can be replaced

Contra:

• sound depends a lot on correct sitting position
• no bass at all below 60 Hz
• could be more airy above 10,000 Hz
• highly problematic impedance response
• 'surround reflector' inside earcups might hurt upon being touched for longer periods of time
• comes without accessories like bag or additional, shorter cable
• short cable comes extra & is nowhere to be found
• conservative, boring design

Last update: 17.03.2015

Review of the FiiO E07K 'Andes' / Avinity USB DAC Mobile (& FiiO L7)

Edit 18.09.2013: As it appears, German distributor Hama has included the FiiO E07K into the portfolio of its own subsidiary company Avinity. It´s called USB DAC Mobile and is, as it appears, structurally identical. Therefore, the following text is valid not only for the FiiO E07K but also for the Avinity USB DAC Mobile.

1. Prologue

The postman delivered it, I kept it and it changed me. Sometimes, my dear Constant Reader, things can be as easy as that. The 'thing' I´m talking about caused me to re-evaluate my reviews, making them more earnest and truthful and it has been in use every singular one of the 180 days that passed since it arrived. I´m talking about a fabulous little amp, the FiiO E07K (or 'Andes'). It is the successor to the widely popular FiiO E7 which was reviewed by NwAvGuy in May 2011. That review concluded with the following recommendation: "The FiiO E7 seems like it should cost more from the moment you lay your eyes and hands on it. And that impression remains when evaluating the performance. The E7 is hard to beat for the price unless you have power hungry full size high impedance cans. It’s also makes a respectable battery powered amp. It’s well worth $99." NwAvGuy has all but disappeared and for that reason I´d like to offer a 'sequel' to his review. I´m not kidding myself, it´s close to impossible for me to arrive at the level of his objectiveness. For one thing, I myself am not an objectivist (no subjectivist either but that´s a story for different day) and for another thing I lack his professional measuring equipment. I have to be realistic about the latter: this blog is a hobby, a way of entertaining myself and others, equipment worth thousands of Euros would be utterly pointless. This article is separated into several chapters, that way you can scroll to the part that interests you the most. The biggest chapter (measurements) is an individual post:

1. Prologue
2. Overview & technical specs
3. The ASIO driver & other peculiarities
4. Listening test preparations & setup
5. Listening test
6. Conclusion
7. Epilogue (tips to milk it as best as you can)
8. Fancy graphs (measurements)

Fig. I. FiiO E07K 'Andes' front

Why do I want to review this unit when countless other reviews already exist? Because no one performed halfway decent measurements of the Andes yet. You´ve seen some? Yeah, on Head-Fi someone measured the EQ. Sorry, but that isn´t what I´m talking about. I don´t want to see how much the EQ of the Andes' boosts treble, I want to see distortions, amounts of jitter, behaviour with headphones, etc. Secondly, all the reviews I´ve read (here and here) performed sighted listening tests. That´s ok but there´s still a difference between good and better sighted tests and I believe that my unique approach is the best and most transparent, non-DBT listening test available. The most important reason however is that no one - I repeat: no one - has yet examined the ASIO driver FiiO offers on their website... Google tells me that most people don´t even know about it. As I´ve already mentionend in the prologue, the E07K forced me to re-evaluate my approach. Hence I was able to improve my method of reviewing audio units - especially headphone amps - to gain superior results. The first unit to profit from my enhanced testing methodology was the re-reviewed FiiO E6 whose article I´ve subsequently rewritten considerably.

Fig. II. Typical usage of the FiiO during the past half year

In the end I´ve had half a year to get to know the E07K; other reviewers (far less magazines) lack that luxury. But don´t think for one minute that those six months available to me have been voluntary: unexpected problems of our PC forced a dormancy upon my audio related activities, those were the true reason I´ve had time to evaluate and re-evaluate the Andes' qualities thoroughly, ending up analyzing it again and again. I´ve used it on almost all of the 180 days in combination with most of my MD recorders and portable CD players (see fig. II.) while I was reading books, as a DAC when I wanted to listen with my low-impedance Sennheiser HD-448 while surfing the net and with my big stereo system (combined with the FiiO L7 to gain a true line-out). The first comparison between my reference files and the Andes-derived files took place in January 2013 closely after purchasing it (the result blasted the FiiO E6 out of the sky). The second and third comparisons were done a week ago. All were realized with my self-developed system of comparing reference files to files that incorporate the sonic signature of the gadget I want to review... but I´m getting ahead of myself. So let´s continue with a general overview, yes?

2. Overview & technical specs

Fig. III. FiiO E07K 'Andes' accessories: felt-line rubber bag, USB cable, two plastic straps, rubber shell,
manual, 4-inch cable with 3.5 mm miniplugs, six rubber feets and two transparent screen protectors

On the photograph above (fig. III.) you can see that the Andes comes with a multitude of accessories. Regarding these consider the price for a moment, it costs just 90,- Euros (Avinity USB DAC Mobile: 180,- Euros (yes, it´s ridiculous considering you can buy the FiiO for half of it)). Then consider its abilities and you´ll see the amount of money spent is ridiculously small... I really wonder how FiiO is able to still make a cut and if they treat their labour force well. I avoid Apple products (others as well) for that reason, knowing that they are manufactured by Foxconn or Pegatron where people are treated like cattle for the benefit of us customers who only want the lowest prices. The connection to Apple I just made is not a coincidence: the design of the Andes (including the cardboard boxing) alludes to gadgets like iPhone or iPod; it shows similarities concerning appearance of solidity, tolerances and visual impression of workmanship. Of course, looks aren´t everything. The anodized aluminum of the Andes feels rather thin and lightweight, the aluminum bodies of many of my MD recorders are of higher grade. The metal buttons, although perfectly embedded, feel slightly rubbery at the touch. And then there is the OLED display of my E07K which is not perfectly aligned but tilted a bit to the right side. I´m complaining on an extremely high level here; general manufacturing quality of the Andes is fine (see figs. IV. & V.). The glass screen is high-grade, seems robust and it, along with everything else, fits very nicely with low tolerances. Even better: the FiiO E07K can be disassembled easily (no Torx screw heads) to for example replace the Li-ion battery (not so easy with an iPhone)... how cool is that? One thing however bugs me: the Andes collects dust like a magnet; I doubt that it´s static-related and although it is a minor nuisance it´s still unnerving 'cause I want to clean it all the time.

Fig. IV. FiiO E07K 'Andes' OLED display, slightly tilted to the right on my unit...

Fig. V. ... generally however build quality is excellent (blue LED signales 'power on')

The entrails of the FiiO are, like its outer appearance, budget conscious but comparably high-class. Many people say that the circuit design of the E07K is similar to that of my E6; if that is true or not I do not know. What I do know is that FiiO exchanged the opamp TI TPA6130 of the E6 to the MX97220 that increases power output on the headphone out considerably. The D/A-converter is the same as in the predecessor E7, a high quality Wolfson WM8740, also used in the more expensive FiiO E17 'Alpen'. In fact, the Alpen is very similar to the Anden: it only differs by having more power, boasting a built-in line-out and it is able to play back 24/192 through its S/PDIF input. USB connectivity on both the Andes and Alpen is provided by a Tenor TE7022L, an IC able to transport signals up to 24/96. Here is the rest of the technical specs (according to FiiO):

Input: USB and AUX
USB Support (max): 24bit / 96kHz
Channels balance: +/-10dB (5dB to either Left/Right)
Gain selection: 0dB, 6dB, 12dB
Digital Volume Control: 0 – 60 step
EQ: Treble - +/-10dB; Bass - +/-10dB (in 2dB step)
Line-out: Bypassable to pre-out (with FiiO L7 or E09K)
Output Power: 250mW (16Ω); 220mW (32Ω); 36mW (300Ω)
Headphone Impedance Range: 16 Ω ~ 150Ω
Frequency Range: 10Hz ~ 220kHz (amp); 10Hz ~ 20kHz (DAC)
Input Sensitivity (0/6/12dB gain): 2.75V/1.38V/690mV
MAX input Level: > 4.5 Vrms
MAX output voltage: > 7 Vp-p
Screen: 1 inch two tones OLED
Power Supply: Internal 1200mAH rechargeable Li-ion battery
Battery life: over 20 hours
Recharging: USB 5V, Less than 180mins to full
Size: 96mm x 55mm x 15.5mm
Weight: 102g

The most important changes to its predecessor are 24/96 support (E7: 16/48) and that it adds several gain levels (sort of like a built-in pre-amplifier). The digital volume control, which isn´t digital at all 'cause it only controls analogue resistors digitally, can be set from 0 to 60 though I would limit it to 50 via the menu since the Andes starts to distort when the maximum setting is approached (see the measurement section). Battery life of roughly 20 hours isn´t very much, I would have liked to see a longer running time but the new opamp probably draws more power - so a shorter battery life in exchange for more power and hopefully superior sound is a fair deal. Unlike others I don´t think that usability of the menu or the buttons is awkward, everything and every behaviour feels natural and logical to me and after a while it can be operated blindly.

Fig. VI. FiiO E07K 'Andes': two headphone outputs. Why?

But I don´t understand why the E07K has two headphone outputs, to me they are as useful as an illness (fig. VI.). If my boyfriend and I would listen to my favourite music at the same time he´d kill me soon afterwards. Instead FiiO could have equipped this amp with a line-out like they did on the E17. All right, this really isn´t any bother at all, I simply ignore the second headphone out. But the FiiO boasts another feature so brilliant that I feel the need to ask why other companies failed to think of it: it has female connectors suitable for a docking station. It´s rated for headphones from 16-150 Ohms, that excludes power hungry cans like my Sennheiser HD-600. To compensate for that FiiO offers the E09K 'Qogir' (109,- Euros), at first glance a simple desktop headphone amplifier able to drive high impedance headphones that at a closer look reveals the male docking counterparts. Thanks to this docking station ability you can place the Andes on top of the Qogir which will then establish USB connectivity, charge the E07K and passes along its DAC signal for the E09K to amplify. The combination of E07K and E09K creates something akin to a stationary high definition soundcard able to drive huge and power hungry headphones yet is still a portable amp (& DAC) at heart.

Fig. VII. FiiO E07K 'Andes' & FiiO L7

But the Qogir isn´t exactly something I´d need. I already have my Xonar Essence STX that contains the same IC used in the E09K, the TI TPA6120. Nevertheless I thought about purchasing it upon realizing in January that I couldn´t use my beloved Xonar Essence ST (PCI version of the STX) anymore. In the end I decided against it because the Andes isn´t 24/192 equipped, it also cannot record. Both are requisites for performing my reviews, I never use 24/192 for general playback but it´s important for measurements and listening tests. If you - like me - don´t need the Qogir you can also buy the FiiO L7 (see fig. VII.) for just 9,- Euros. It´ll add a line-out to the DAC function (use the LO BYPASS switch for it) and will pass USB signals through (including charging) - very handy indeed. To attain the digital input of the bigger E17 you could also buy the FiiO D03K (27,99 Euros). It´s a tiny DAC with optical and RCA digital inputs (to improve a vintage portable CD player for example) and from reviews I´ve read it´s able to beat external DACs ten times its price which - if true - would mean that it offers spectacular value for money. What? No, I don´t work for FiiO but I could end up with half of their product catalogue anyway, they just leave the impression that they cut the crap other boutique manufacturers attach to their products.

3. The ASIO driver & other peculiarities

Fig. VIII. FiiO E07K 'Andes', ASIO driver samplerate configuration

They aren´t always successful at cutting the crap, sometimes they end up creating it by means of an ASIO driver in an effort to offer some additional value to their customers. When you connect the Andes to a PC using a MS Windows OS (XP, Vista, 7, 8) a generic driver provided by Microsoft through their Universal Audio Architecture will be installed. This is possible because the FiiO is a USB device fully adhering to the USB Audio Class 1 standard for which this driver has been programmed. Therefore, if you don´t use ASIO it´s not necessary to install FiiO's driver, the Andes will work perfectly without it. In fact, I strongly advise against installation. The main problem of FiiO's ASIO driver is that it resamples without you being aware of it. Imagine that you configured it to 96 kHz in the ASIO control panel (see fig. VIII.). But what happens if you play back 44.1 kHz without changing anything? Under Windows 7 (presumably also on Vista & 8) it´ll resample the 44.1 kHz stream to the format you defined in the configuration panel, in our case 96 kHz, all the way using the Windows 7 audio stack which sucks at its job. The result is distorted audio (see measurement section), obscuring the Andes' qualities. I´ve also tested its performance on Windows XP (which uses a different audio architecture); I´ve found that it doesn´t resample but adds some distortions for which I'm unable to find any reason.

Fig. IX. FiiO E07K 'Andes', ASIO buffer size & bitdepth configuration

This is the first time I encountered an ASIO driver unable to switch samplerates by itself. My E-MU 0202 USB switched samplerates automatically and told me so, while my ASUS Xonar Essence STX doesn´t remind me it changes samplerates anyhow. Both were and are following exactly what an ASIO capable program told or tells them to do (-> direct control of hardware). Equally peculiar: when playing ASIO streams other sounds NOT using the ASIO protocol are still audible. This doesn´t normally happen - unless the interface employs a hardware mixer which the FiiO of course lacks. I suspect that FiiO's driver isn´t a true ASIO driver at all, it´s possible that it´s only a 'wrapper' for a plain, not very well programmed WDM (Windows Driver Model) driver. It encapsulates (wraps) a plain, non-ASIO signal stream inside the ASIO protocol for appropriate software. WASAPI and Kernel Streaming react in unexpected ways using this driver too. With JRiver Media Center and foobar2000 alike Kernel Streaming on Windows XP produces errors like sped-up audio (corresponding to differing samplerates), drop-outs or complete silence. WASAPI on Windows 7 is worse, most of the time it doesn´t work at all, crashes foobar2000 and produces silence on JRiver Media Center. The possible reasons for these errors remain elusive, I was unable to establish a behavioural pattern.

Fig. X. ASIO4ALL: if you absolutely need ASIO, use this driver extension

Almost all of this can be avoided if the generic Microsoft driver is used: WASAPI now switches samplerates automatically, precisely following commands issued by foobar2000 or JRiver Media Center. On Windows XP it doesn´t look so rosy; Kernel Streaming doesn´t work at all, both programs stay silent. Direct Sound works of course but who wants to use that, eh? Don´t panic, there´s a solution for this problem, a solution that single handedly will also wipe away the fact that the generic MS driver doesn´t support ASIO. It´s called ASIO4ALL (see fig. X.) and it is, just like FiiO's driver, an ASIO wrapper, in this case one that works flawlessly. On Windows XP it wraps the ASIO protocol around a stream sent by any WDM driver, or more precisely, its kernel stream. Curious, isn´t it? As long as Kernel Streaming is embedded in the artificial ASIO protocol created by ASIO4ALL the Andes works perfectly, even changing samplerates correctly on the fly. But the moment a program starts to use Kernel Streaming directly, playback fails. Before ending this chapter I have to say something about ASIO4ALL: it is not a driver. It is a wrapper 'wrapping' the ASIO protocol around regular Kernel / WASAPI signal streams. It does not bring along its own driver, it attaches a small piece of software to any existing driver, making control of faked ASIO streams possible. People always get this wrong, most of the time they refer to it as a hardware driver which it simply isn´t nor wants to be.

4. Listening test preparations & setup

Fig. XI. FiiO E07K 'Andes' LO BYPASS switch and AUX IN were used a lot for the listening tests

Not long now and I´ll be finished. Promise. As you may or may not know I use a special testing methodology to obtain the most neutral, sighted listening test results anywhere. Basically, I compare anything that plays music directly to the files it plays. Many magazines, forum members or website owners compare the sound of some gadget to the sound of another gadget. In almost all cases the latter gadget is something extremely expensive, luxurious, whatever. But there´s an important question no one asks: what if this exotic gadget isn´t neutral? What if it adds more bass, treble, dynamics or euphonic colourization? Can we really trust the manufacturer of this gadget to say the truth about this "most advanced and best sounding ................ on the market"? The answer is a simple "NO". Most high end hardware is designed to put on a fun show with certain musical styles or genres. One DAC might sound especially well with classical music, another DAC with Rock'n Roll... now guess which one will suck at Rock'n Roll. Customers buying this 'sounded' hardware are not aware of this... and why should they? In my experience people who listen to one genre rarely listen to another, in case they (against all expectations) paradoxically should do so, they´re fucked. "This cannot be true!" you´re exclaiming now... well, it is. I´ve found budget hardware to be capable of almost exquisitely neutral music playback. And if cheap BluRay players almost sound like the reference how can some high end apparatus be superior?

Above I have pictured my method for capturing the sound of the FiiO E07K when using its DAC function exclusively. It is linked to my laptop and configured to 24/96. At the same time it´s connected with an RCA cable to the line-in of my ASUS Xonar Essence STX inside my desktop PC. I then play back five reference files with the FiiO (using foobar2000), its output recorded in 24/192 (using ASIO) by the Xonar Essence STX. After the files now containing the sonic signature of the Andes have been recorded to the PC I synchronize and level-correct them so that they have precisely the same starting point & gain as the reference files (gain differences = sonic differences). Finally, the recorded files are resampled to 24/96 with the result that they have the same properties as the reference files, are exactly as loud yet still contain the FiiO's signature. I then proceed to compare the recorded files to the reference files in a listening test (in this case I repeated the whole procedure two times, for the line-out (using FiiO L7) and the headphone out respectively).

To find out of if the analogue input of the FiiO changes the sound I have to work a bit differently. The Andes is a headphone amp and amplifies any audio signal it is fed. Therefore I need it to amplify something and this something is my Creative Labs Soundblaster X-Fi HD USB. Which also means I´ll require new reference files, I cannot use my original files anymore since the recorded files then would include the combined sound signature of two units. Because of that, new reference files are created by playing back my original files and recording the line-out of the Soundblaster the same way the DAC of the FiiO was captured above. The rest of the procedure is the same (synching, level matching, resampling) but the listening test is obviously skipped. Remember: so far I have produced new reference files only.

To create files containing the sound signature of the Andes I simply loop it into the signal chain where it then amplifies the signal coming out of the line-outs of the Soundblaster X-Fi HD USB. The rest is similar to the two examples above.

All of this is quite elaborate but I don´t know any other, less time-consuming way to obtain neutral results. My whole procedure can only work of course if I assume the input of the ASUS Xonar Essence STX being able to capture with perfect transparency. If that is or isn´t the case I don´t know, I just know that my Xonar Essence STX is the best I´ve got. I daresay only this: the best analogue recordings I´ve ever performed were made with the analogue input of the Xonar Essence STX. The rest of the setup is as follows: the Andes and the X-Fi HD USB were linked to the respective computers with my Audioquest Forest USB cable, the RCA interconnect cable was the Audioquest King Cobra. The 3.5 mm to 3.5 mm interconnect between the FiiO's output and the Xonar Essence STX was the FiiO L8, manufactured for them by Japanese company Oyaide. Gain pre-amplification on the Andes was configured at +6 dB (for analogue in as well as USB), volume setting on its headphone out was 50. When used with the L7 adaptor line output level was fixed at approximately 1.35 Volts. Playback level of the X-Fi HD USB was set to 0 dBfs (maximum volume, both on headphone out & line-out), recording level for the Xonar Essence STX was set to 0 dBfs (maximum) too. Input impedance of the Xonar Essence STX is - according to Stereophile's measurements by John Atkinson - 4300 Ohms.

5. Listening test

Fig. XII. FiiO E07K 'Andes' close-up

AUX in (analogue line-in)

What people say about the circuit design of the Andes being similar to the E6 might be the truth; the sound of its line-in shares many traits. Lowest and highest frequencies are diminished, upper bass sounds as if increased, giving singers more chest and instruments more body (very apparent with the track from 'Ray of Light' & the Vierne organ recording). Dynamics are more timid compared to the reference files, the FiiO amplified results lack snap, punch and 'bite', the tracks sound univolving. Timing however is a close match over the whole frequency band. Resolution and rendering of details strongly resemble the references, slurring very little details or high frequency differentiation. But it´s especially evident around the mids where articulation is pristine. When it comes to the virtual stage the Andes makes it a tad more instable, marginally loosing focus and blurring position and dimension of instruments. The character of connected devices is retained well, the sound signatures of the X-Fi HD USB, my MD recorders or portable CD players are transported almost without flaw. The way I describe all these deficiencies might come across as if the FiiO wouldn´t be very good, yet they are, with the exception of sonic balance and dynamics, not readily audible. The sound signature of the FiiO's line-in is warm, friendly and calm, it´s not impeccable but good enough to beat the E6 effortlessly and it´s absolutely qualified for good music playback. I wouldn´t pair it with already laid-back sounding sources though, that might create too much of a good (or bad) thing. BTW, German AUDIO magazine rewarded its sister model Avinity USB DAC Mobile 80 points for sound quality (from their maximum of 100) in a review for their October 2013 edition.

Sonic Balance:

Dynamics:

Resolution:

Stage / Ambiance:

Character:

USB DAC

The very same AUDIO magazine awarded 85 points for sound to the Avinity for its DAC part... naturally they listened with the supplied USB cable. I on the other hand did all my listening tests with my Audioquest Forest. The editors of that magazine apparently heard a different sound signature in their listening sessions, either because of the cable or because they don´t use my method of comparing devices, both are likely candidates. I myself had a hard time hearing any differences at all. When I didn´t know what I was listening to, I regularly confused the reference files with the files derived from the Andes' DAC section and vice versa. I needed countless hours and many listening sessions, in some cases months apart, to arrive at a conclusive result. BTW, there were no differences between the L7-derived line-out and the headphone-out. On both outputs dynamics could still profit from a bit of 'oomph' but it´s barely detectable. Sonic balance continues to be a tad on the voluptuous side, still missing a now insignificant amount of deepest and highest frequencies. The impression of virtual stage is a match regarding size, dimension, focus and intelligibility, if there's something to complain about it´s a minor impairment of stability. But the difference is so small that I feel the need to introduce half points for my ratings. Everything else, resolution and characer, is extremely close to the references. All of the described shortcoming are faint, errors are so minuscule that it takes a long time to hear them, I cannot even preclude that I have experienced a prime example of a placebo effect. Because of this I assume that it´d be hard to improve the sound any further, at least not without some effort. Take the FiiO E17 'Alpen', maybe it is able to boost sound quality, but I doubt it; there simply isn´t much left to advance anyway. Articles reviewing the Alpen often emphasize that it sounds more engaging than the Andes... which can mean anything, from featuring more bass and treble to boasting superior dynamic capabilities. So for the time being let´s summarise the listening tests with the following sentence: the FiiO E07K is an excellent USB DAC.

Sonic Balance:

Dynamics:

Resolution:

Stage / Ambiance:

Character:

6. Conclusion

Fig. XIII. FiiO E07K 'Andes' in all its glory

The product finish of the Andes is very well done, it comes with a bunch of convenient accessories, is small enough to be portable, not big enough to be too clunky and can be handled blindly. Just attach it to the back of your smartphone or your portable player with the enclosed rubber straps and enjoy a sound quality you wouldn´t have expected coming from those devices. Just like every (well engineered) headphone amplifier it´ll get rid of impedance output mismatches, it will also achieve deafening volume levels if you so desire. But amplifying portable devices is not all the E07K can do. Do you own a laptop, desktop PC, a tablet, a Mac, subnotebook or netbook and do their headphone outputs / line-outs sound fucked up or simply lack enough gain? For all of them the Andes is the perfect solution. Just plug it in and enjoy. No additional driver installation, no hassle, just perfect sound (there are one or two things you can do to make sure extracting perfect sound quality; just continue reading). Basically, by buying this thing, you´ll get two things fused into a single, very nice and convenient package. Yes, I can recommend the FiiO E07K 'Andes' without reservations. Just stay clear of the ASIO driver FiiO offers and you´ll be rewarded with an audio unit that is able to amplify any audio output with good results. Use it as an USB DAC and you will listen to audio quality you won´t have ever expected from something as inexpensive, tiny and beautiful as this. Avoid the Avinity USB DAC Mobile - you can have the same sound for half the money when buying the FiiO. Speaking of which, they will soon release a digital, high definition audio player here in Europe, from what I hear this FiiO X3 is technically very similar to the E07K... I can´t wait to buy it. In the meantime: thank you, FiiO, for releasing this wonderful device and thank you too, my dear Constant Reader, to bear with me during thís very long and detailed article. I hope you are, like me, a bit smarter now regarding the FiiO E07K.

7. Epilogue (tips to milk it as best as you can)

Fig. XIV. FiiO E07K 'Andes' - extract everything you can

1. Avoid the ASIO driver provided by FiiO

It measures and sounds bad (by introducing errors to a normally perfectly clean signal), it is not one bit convenient and one doesn´t know what it´s doing, nothing about this driver is transparent. Use the Microsoft-provided, generic USB audio device driver (dated November 2010) instead, it´ll function almost without error. If you´re desperate for ASIO capability, use ASIO4ALL.

2. Make sure to configure the Windows sound properties correctly

Fig. XV. tick these SPDIF (MS name for the E07K) interface capabilities

Fig. XVI. Raise the sound level to its maximum

Fig. XVII. Make sure to tick those boxes, only then WASAPI
will be used at its maximum potential

I apologize for the German designations, I was too lazy to switch Windows to another language. You´ll get the picture anyway, it´ll look the same on your PC, wherever you´re coming from (except for Asian readers; sorry). To reach the settings pictured above right-click the loudspeaker symbol in the taskbar -> left-click 'playback devices' -> right-click 'SPDIF interface FiiO USB DAC E07K' -> left-click 'properties'. Fig. XV. shows which boxes to tick, though it isn´t absolutely necessary if you remember to tick those two boxes shown in fig. XVII. Those are crucial if you want the WASAPI interface to work at its best (meaning: automated samplerate switching, retaining bit depth). Equally vital for bit perfect sound not impaired by the Windows audio engine is raising playback level to its maximum setting (fig. XVI.), otherwise you will inadvertently hamper resolution (by lowering bit depth). If you want to change the playback level, do it only on the FiiO, or when using the L7, on the amp downstream. I should mention that these recommendations do not apply to the FiiO alone, many interfaces using WASAPI exclusively can be lifted to their top performance if you heed this advice.

Experiment with different USB cables

I´m a part-time subjectivist, I told you so. My listening tests were done while using my Audioquest Forest USB cable. I was unable to find any measurable evidence for sonic differences between several USB cables, yet I heard them and was able to pinpoint two of them performing a DBT. In case of the FiiO Andes I also attempted a listening test using the enclosed USB cable and I can summarize that it changes the sonic signature of the E07K slightly but noticeable. The stage is widened and flattened, resolution improves, the slight voluptuousness of the sound disappears almost completely. On the other hand the Andes now sounds too analytical, a tad strident even. Dynamics are unchanged. For that reason use different USB cables to create synergy effects with attached headphones - but do so wisely. I wouldn´t recommend spending more than 40,- Euros for a single USB cable, too many people are punked by greedy and lying manufacturers.

Choose gain levels wisely

The Andes offers three gain levels, selectable via its menu. The first one (0 dB, 2.75 V sensitivity) should be used for stationary sources like CD players, network streamers or BluRay players, the second (+6 dB, 1.38 V sensitivity) for line-outs of portable players like MD recorders or very loud headphone outputs and the third one (+12 dB, 0.69 V sensitivity) applies to very weak headphone outputs. The factory preset of +6 dB works fine on many occasions. Attention: If you don´t select them appropriately you will overload the input, leading to distorted sound. You don´t want that, do you?

Don´t come too close to a volume setting of 60

I´ve shown in my measurement section that the Andes starts to distort the closer you approach the maximum volume setting its headphone amplifier allows. Thankfully, you can limit the volume through the menu to a value that is safe to use. I´d recommend a setting of 50.

Prolongue the lifetime of the built-in battery

Li-ion batteries are impervious to many flaws associated with batteries from 20 years prior. The memory effect (of Ni-cd for example) is a concept alien to them, you can charge them whatever their charge level is, they are small and can store lots of electrical energy. But they still have two major weaknesses: Li-ion accumulators don´t work that well when temperatures are below freezing, they also have a high discharge rate when not in use. Which means: if you are not planning to use your FiiO E07K for some time, store it in a cool, dry place with the battery at a charge level of 40%-50%. If you don´t follow this advice, the battery will age much faster, won´t hold the same amount of energy after charging and will be gone in two to three years. If you take care of it like I recommend you will enjoy it for years to come. BTW, this tip applies to all Li-ion batteries!

Last update: 18.09.2013