Review: FiiO X5 (loaned by FiiO)

Disclaimer: this article is not an example of native advertising.

I wasn´t paid by FiiO to write this review, nor did I receive any compensation.
The unit to be reviewed was loaned to me for several days after which I sent it
to the British Isles to another reviewer. To me, it´s important to tell you this,
because there are places out there not telling you that they´re writing
reviews where the result has been predefined by the manufacturer.

1. PROLOGUE

Sometimes life is indeed like a box of chocolates, you never know what you´re gonna get. But nobody ever tells you that you might not like the things you´re getting. In my case, the 14 months since my last article were Hell. Taxing for both my boyfriend and me, he now calls it his "Annus horribilis" - and nothing else could be a more fitting expression. I won´t dwelve into details, I´ll only say that the last year involved the passing of a family member. In light of this, every appeal some gear aimed at music reproduction has, has paled. But before I digress into a discussion about what's important in life, I´ll say that for you, dear Constant Reader, the only important thing is: I'm back!

Considering the fact that the successor of the FiiO X5 (2nd gen) has just been released two days ago, it is ironic that I should review the FiiO X5 (1st gen) before the older FiiO X3 (succeeded as well by the X3 (2nd gen)). I´ve owned the latter since October 2013 and, I have to admit, haven´t been that happy with it. Why? I expected a gadget without firmware crashes, featuring pristine decoding of lossy formats, fast reaction times and neutral sound. Instead I received the opposite. In December 2013 FiiO announced on Head-fi, that several X5-preview-models were to be delivered to willing reviewers all over the world. Though my initial application was rejected, I nonetheless did receive the European preview model a few months later. I was supposed to test its newest beta-firmware to measure its performance with lossy codecs, a task I gladly accepted. After all, it was me who in November of the same year started a lengthy and tiresome discussion concerning the quality of lossy decoding on both FiiOs. For convenience reasons, this article is seperated into several chapters, that way you can scroll to the part interesting you the most:

1. Prologue
2. X5 Competition
3. HiRes DAP - why?
4. Specs & features
5. The importance of firmware
6. Listening test
7. Conclusion
8. Fancy graphs (measurements)

Is it a bird? Is it a plane? Is it a 1st-generation iPod? No, it is a FiiO X5!

2. X5 Competition

Just like the models from Astell&Kern, Sony and others like iBasso, or even the laughable Pono (righteous my ass), the FiiO X5 is a HiRes-capable DAP. In comparison to most of these models though, it isn´t as ridiculously expensive nor is it loaded with marketing hype. The Sony NWZ-ZX2 costs a whopping 1199,- Euros, the AK 240: 2.400,- Euros. And yet they´re still incapable of powering lots of cans: the expensive Sony for example achieves so little gain that it can´t power 75 % of all headphones out there. The Sennheiser HD-600 on the Astell&Kerns? Impossible. You could spend much less money and buy the FiiO X5 for 399,- Euros.
It cannot play videos, isn´t able to connect to devices via Bluetooth / NFC or act as a DLNA streamer, it also doesn´t feature a touchscreen like all the other players. Instead, you´d get a sort of oldfashioned click-wheel on the X5 (hello, iPod 1st gen), buttons and even more important: a powerful headphone output. All of this doesn´t change the fact that the most dangerous competitor for the X5 are FiiO's own X3 and X1: both were/are cheaper (219,- / 99,- Euros) and offer - with the exception of the X1 - exactly the same features (the X3 lacks OTG). Instead of a clickwheel, the X3 sports buttons, a really crappy LCD display, a different audio path using less ICs and one MicroSD card slot instead of two. The X1 looks like a smaller X5 and lacks a second MicroSD card slot, a digital out, a line-out and the Hi-Gain option for high-impdance headphones.

Very competitive rival to the X5: FiiO's very own X3

3. HiRes DAP - why?

Good question. Why should a DAP dedicated to music playback only be an option when every smartphone can do the same... and contains a camera, the ability to add apps, surf the web, etc. And I won´t even mention that the expression "HiRes" is thoroughly misleading (extended frequency response and lower noisefloor would be the correct designations). Easy answer: portable HiRes DAPs are equipped with well engineered and powerful headphone outputs. At least when it comes to FiiO. But the X5 (the same goes for the X3 and, partly, for the X1) is much more than a simple player. Because FiiO likes to equip their players with features otherwise only found on the more expensive competition, the X5 can do many things you´d normally need several, individual devices for. It´s a portable DAP, USB-DAC, USB-to-S/PDIF converter and it acts as a stationary HiRes player via its line-out. Compared to the smartphones people usually use, the X5 will be able to drive many headphones - even difficult ones like my Sennheiser HD-600 - without problems, impedance-related frequency errors or low gain are absent. On smartphones you have weak headphone outputs, furthermore, they aren´t able to play often-used formats like FLAC (the iPhone, just to name one), you´d need an extra app for them. All of this is solved by the purchase of the FiiO X5.

FiiO X5, backside fashioned out of aluminum

4. Specs & Features

The heart of the FiiO X5 is a somewhat older SoC, the Ingenics 4760B ('XBurst'), launched in 2010. It´s a low-cost MIPS design, aimed at smartphones and the like. It features two cores (the second core serves the GPU) and includes an FPU (floating point unit). This SoC is responsible for everything, ranging from decoding media formats to drawing display elements. The D/A-converter is a Burr-Brown PCM1792A, an IC usually found in stationary digital devices of the more expensive kind. Headphones are amplified by two OPA1612 and two LMH6643. All chips inside the X5 dealing with audio reproduction are supplied by Texas Instruments, a fact the company likes to gloat over. As for the rest of its specifactions, please refer to the following itemization:

General specs

Dimensions: 64.6x114x15.6 (WxLxH, mm)

Weight: 122g

Display: 2.4" 260,000 colors HD IPS Screen at 400x360

CPU: Ingenics 4760B 600MHz Dual Core

DAC: PCM1792A, supports 192KHz/24Bit

Outputs: 3.5mm Headphone jack, 3.5mm Line-output, 3.5mm Digital Coax output

Storage: 2 x microSD slots (currently max supported 128GB x 2)

Battery: 3700mAh Li-Polymer Battery, up to 15 hours playback time

Headphones impedance range: 16~300Ω

Gain selection: 0/6 dB 

Line output Level: > 1.5 Vrms

Headphone output power 1: > 460 mW@16Ω

Headphone output power 2: > 255 mW@32Ω

Headphone output power 3: > 28 mW@300Ω

Headphone output impedance: <0.26Ω

Headphone output crosstalk: >75 dB@1KHz

Headphone out THD+N: < 0.003%@1KHz

Frequency response: 20Hz~20KHz（+/-0.1)

MAX output voltage: > 8 Vp-p

SNR: > 115 dB

MAX output current: > 150 mA

Supported formats

Lossless: APE(fast:): 192K/24B; APE(normal): 96K/24B;

APE(high): 96K/24B; FLAC: 192k/24B;
WAV: 192k/24B; WMA 9.1 LOSSLESS: 96k/24B;
Apple Lossless 192K/24B; DSD 2.8224;

Lossy compression: MP2, MP3, AAC, ALAC, WMA, OGG

FiiO X5 size comparison against the Sony MZ-R 909, an ancient MD recorder

But what about manufacturing quality? Let me put it this way: should you encounter an intruder in your house you can use the X5 to knock him/her unconscious. It is heavy and feels like a portable tank. It is neither small nor fragile (the MZ-R 909 pictured above looks & feels flimsy in comparison), once you grab it it conveys the haptic of something engineered for military use. This impression doesn´t extend to the clickwheel though (see the image below), it feels like a plate made out of cheap plastic (which it is, only covered by a sheet of rubber). It turns too easily for my taste, it should have offered more resistance upon moving it. My criticism continues with the aluminum 'enter' button in the middle which wobbles the moment you press it. Everything concerning the clickwheel feels a bit tacky. Compared to the rest it is quite the difference, if you ask me.

FiiO X5 clickwheel: rubber-coated plastic with aluminum button in the middle

Every jack, whether it´s the digital output, headphone out or the USB port, is manufactured well, gripping plugs tightly. The display shows good contrast and decent colour temperature from every angle. All in all, it is exceptionally manufactured... but I would have loved to have another colour option. Maybe white, gold or silver, you know; something fancy that would be pleasing to the eye (guess what: I acquired the X1 in gold). The design and haptic of the X5 carry a strong technical vibe, people looking for smoothness or elegance should look elsewhere. In part, this can be rectified somewhat by several accessories FiiO and others are offering. Just have a look at the image below listing several possible additions.

FiiO X5: selection of accessories

5. The importance of firmware

Since releasing firmware 2.0, FiiO likes to brag about the 32 bit floating point decoding of some lossy formats, namely MP3 & OGG. They describe their decoding as industry leading; that is the truth and I´m partly responsible for this as I started a discussion in November 2013 in the X3-thread on Head-fi. I literally bombarded FiiO with emails regarding their then botched decoding of lossy formats, when that didn´t prove successful, I wrote the post I linked above. Shortly after, others started to chime in while I continued providing measurement data revealing how bad the X3 was decoding MP3, OGG and WMA. To make a long story short, FiiO started to work on revamping their decoding engine. It took them half a year to pull it off, the results are stellar and well beyond my expectations. The X5 and X3 now decode MP3, OGG and WMA as pristine as foobar2000. Which is in fact industry leading; I don´t know any other company producing portable players that decode these lossy formats the way the devices from FiiO do. So what I called 'bragging' at the start of this paragraph is completely justified. I have to mention Head-fi member JoeBloggs, who works for FiiO and was incredibly helpful in getting it done (he will read this article and he will know what I´m talking about).

On the other hand, the opportunity to play around with so many different firmwares poses a problem. You see, many of them cause the FiiO X-players to sound different. Yup, I know what I just wrote and believe me, I feel ridiculous. I really don´t know how FiiO is able to slightly alter the sound of some player just by changing a tiny piece of software. I measured several different firmwares on the X3 and on the X5 and couldn´t find significant differences. I did some listening tests, sighted and double-blind, and was always able to confirm differences. I would love to be contacted by someone who could explain to me how this can be possible. Anyway, I will come back to why it poses a problem after I have finished my listening test.

Outputs on the FiiO X5: digital output, line-out and headphone out

6. Listening test

Headphone out

I reviewed the X5 using firmwares 0.01a, 1.17, 1.20 and 1.21b... which makes the description of the sound somewhat difficult as the FiiO kept changing its sound with different firmwares. I reviewed it using FLAC (24/96, 16/44.1), WMA Professional (24/48), AAC (48 kHz) & MP3 (48 kHz), finally settling on firmware 0.01a - which was the first and - in March 2014 at least - the only one that got the decoding of most lossy codecs right.

Using that firmware and a combination of double-blind and sighted listening, the X5 wasn´t a bad player. It also wasn´t a good player. Yet you can read several reviews all over the web where reviewers allocate almost magical properties to its sound - which isn't true. The overall perceived EQ was balanced, only missing a bit of treble and bass. From all the three FiiO X-players I´ve heard (X1, X3 & X5) it certainly is the most balanced. But: dynamics weren´t up to snuff. This player sounded 'little' and timid when it came to rendering transients, exploding bass drums or crisp cymbal crashes. The staging suffered, too: soloists transformed into cardboard characters; while my reference files were holographic and three-dimensional, the X5 sounded flat, wide and two-dimensional. The lacking dynamics wouldn´t have been too bad in the long run... but the missing spatiality made me sad. I reviewed it using several headphones: Sennheiser HD-448, HD-558 & HD-600, I could observe this 'cardboard'-stage with each one of them. Despite these shortcomings, it was very capable of retaining the character of the music it was playing.

And now I´m coming back to the problem of different sounding firmwares. When I received my FiiO X3 in October 2013, well, I hated its sound. In the beginning, it badly lacked at spatiality, just like the X5. It took FiiO almost a year to come up with a sound one could listen to without missing anything (FW 3.00). Before that I listened with the Sony MZ-R 50 or the Sony NW-HD5; both amped by the FiiO E07K, they were clearly superior. In December 2014 I bought the FiiO X1; when FW 1.40 was released a few weeks ago, I again noticed a change in spatiality. Every FiiO X-player so far has matured long after sales had started (Philips calls this principle "banana"; they ripen while they´re at the buyers home). Very problematic for first impressions, I think. So it´s very possible, even likely, that the X5 sounds different at the time of writing. After all, in April FiiO released FW 2.50 for the X5 (and the next beta is already underway) but, since I don´t have it anymore, I cannot re-test it in order to determine if it really sounds different. For that reason I have to rate it like this:

Sonic Balance:

Dynamics:

Resolution:

Stage / Ambiance:

Character:

Line-out

It sounded much better through its line-out. Why? No idea. But the same thing applies to the X3, too. Via its line-out, the X5 sounded almost like my reference files, lacking only a tiny bit of treble and bass. Detail retrievance was on par with my reference, only differentiation suffered slightly. Dynamics? No problem anymore. Surprised? Yeah, me too. Spatiality? The same. Holographic, three-dimensional, just like my reference files.

Sonic Balance:

Dynamics:

Resolution:

Stage / Ambiance:

Character:

USB port, two MicroSD card slots for (right now) 256 Gb of storage space

7. Conclusion

Built like a tank, looking like a tank, sounding, to me, like a little cat at the time it was staying with me. How to conclude a review for a device everyone else seems to love but I don´t? Especially when the company engineering it has been so incredibly forthcoming and friendly to me and others? Let's sum up the obvious stuff: the FiiO X5 looks good, it can do a lot of things that may come in handy. It not only is a portable DAP, it can also be used as a DAC for your PC. It can play almost any codec you throw at it: FLAC, MP3, APE, WMA (including the rare Professional variant), OGG, even the unnecessary DSD. The display looks good from every angle, using its interface was wonderful. Less good are the clickwheel and the size and weight of the whole unit. Wrapping up, it´s a robust, feature-rich DAP. On the other hand, the sound issue remains. It wasn´t sounding well through its headphone out, at least when I was reviewing it using an alpha-firmware more than a year ago. I´m confident that FiiO rectified most of the sound issues I described. Of course, I cannot be sure so in the end it´s up to you, dear Constant Reader, if you want to purchase it or if you spend a little less money and get either the X3, the X3 (2nd gen), or even the X1 instead.

A beautiful, big and robust booty, don't you think?

8. Fancy graphs (Measurements)

Headphone out

RMAA-generated spreadsheet, showing results for three headphones

Frequency response

Noise level

Dynamic range

THD + Noise

Intermodulation distortion

Stereo crosstalk

Phase delay, Sennheiser HD-558

Phase response, Sennheiser HD-558

Jitter, 24/96, headphone out

This must be the best headphone output I´ve ever measured. Never before have I seen an output lacking phase distortion of any kind; remarkable. The noisefloor is at -114 dB, this is professional level. Total harmonic distortions are low, intermodulation distortions show that the Sennheiser HD-558 is a headphone that is difficult to drive. Have a look at the weird looking noisefloor and the low-frequency IMD when the X5 is amping it. I don´t know how audible those distortions are, though. The most interesting thing however is the graph showing jitter: while it is pretty low, it´s different from the amount of jitter found on the line-out. Have a look at the next graph:

Line-out

Jitter, 24/96, line-out

RMAA quality assessment, 24/96

Frequency response, 24/96

Noise level, 24/96

Total harmonic distortion, 24/96

Intermodulation distortion, 24/96

Intermodulation distortion, sweep, 24/96

Phase delay, 24/96

Phase Response, 24/96

Impulse, 24/96

Odd, isn´t it? Jitter is lower on the line-out even though both outputs use the very same DAC. But instead of having no phase distortion on the headphone out, you have plenty on the line-out. IMD is a bit lower, total harmonic distortion is much higher. On other portable gear I´ve measured, it´s usually the other way around. And, of course, there is a very, very slight channel imbalance which is probably insignificant. Absolute phase is retained - always good. One thing is for sure however: for a portable device, it measures very well.

Last update: 19.06.15

Spectacular sounding MiniDisc tweaking - FOR FREE!

Introduction

The following Article concerns itself with a piece of software called an Equalizer. Removing certain frequencies with this EQ enables the ATRAC codec necessary for any MiniDisc recorder to encode any piece of music in a superior way. Substantial proof will be offered by means of measurements as well as musical examples.
A warning: if you are lazy or if PC-based audio is a complete mystery to you this article isn´t for you. You also won´t be happy if you think that an equalizer is one of the devil's minions (an opinion clearly not based upon facts). Furthermore, the significant sound improvements described here require you to spend some time with your music, it means work. If you can´t afford the necessary time, you probably aren´t interested in good audio quality coming from MiniDisc at all. Or are you? ;)

Basics of lossy encoding

Lossy (or perceptual) codecs were developed for only one thing: making audio smaller without you, dear constant reader, noticing it. Using a datarate of, say, 128 kBit/s you´ll receive a file the size of only 5 megabytes (before: 50 megabytes). Every lossy codec available on the market performs this 'shrinking', it doesn´t matter if it´s ATRAC, MP3, AAC, OGG or WMA. How do these codecs achieve this? They 'erase' or 'alter' parts of any musical material, getting rid off things our ear cannot perceive anyway. Erasing certain parts of any object reduces its size which is most convenient for portable players not having terabytes of available space; they can store more music that way. In the article that follows I will compare ATRAC (necessary for MiniDisc) to MP3. Both codecs are equally old (20 years), yet MP3 is still in development. ATRAC however was declared dead in 2004 with the introduction of Hi-MD, since then it hasn´t been improved. ATRAC is effectively one of the worst codecs around, it doesn´t help that its datarate is comparably high (292 kBit/s). It could have been more effective if Sony would have decided to fuck their desire for power constraints (a superior ATRAC IC would have drained battery power faster). Well, we have to work with what we´ve got and how we are able to improve it. Anyway, the following chapters will show you the most important basic instrument any perceptual (lossy) codec employs to fool your ear... or more precisely, your brain (Fig. I):

Fig. I: Equal-loudness contour, logarithmic scale (copyright: Wikipedia)

On the left of Fig. I you can see the Sound Pressure Level, measured in dB. The line below presents several frequency points of the entire frequency range our ear can hear (20 Hz to 20,000 Hz), measured in Hz. Now take the highest frequency at 16,000 Hz; it would need a level of roughly 25 dB to be perceived as loud as the 4,000 Hz tone. The key thing you have to understand is the difference between actual levels and perceived levels. Our ear itself listens with almost perfect precision, but our brain decides what part of the received audio material is kept. Our brain has been 'tuned' over the course of several millenia to recognize the human voice with immaculate precision, the area from 2,000 to 4,000 Hz is the most important frequency band  with the highest sensitivity. So listening sensitivity of the ear/brain combination sucks at low and - especially - at high frequencies. Those frequencies weren´t necessary for survival, so they have been 'dropped' as a result. Which means that we have to make signals at those areas much louder. But it also means that we´re unable to hear grave errors at low and high frequencies - and that´s where perceptual (lossy) codecs come in:

Fig. II: Multitone signal, -6 dB, .WAV, 24/44.1 (linear scale, Hanning)

Above (Fig. II) you can see a multitone signal (.WAV) in 24 bit and 44.1 kHz which consists of more than 100 seperate sines. Frequency response ranges from 0 to 22.050 Hz. There aren´t any errors to witness (the thickened bases of the several sines are caused by imperfections of the Hanning windows function used to display the results). Compare that to the same signal, encoded with MP3:

Fig. III: Multitone signal, -6 dB, MP3 (Lame, 256 kBit/s), 24/44.1 (linear scale, Hanning)

It´s evident that something has been added by the MP3 compression (Fig. III). This something is simple quantization noise, inherent to every digital system. In this case it´s at roughly -90 dB (original .WAV file: -144 dB). This amount of noise also reveals how lossy codecs work. It is always said (even I did so above) that they 'remove' or 'erase' parts of the music with surgical precision. Well, it isn´t true, they don´t really 'remove' anything (ignore the cut-off at 19 kHz for a sec'). What any lossy codec does instead is decreasing bit-depth dynamically, taking into account complexity, gain and composition of the signal. Example: a clarinet, formerly having a resolution of 24 bits now has a resolution of perhaps only 6 bits. The remaining 18 bits resolution are non-existent anymore which - BINGO - creates quantization noise. Effectively, the quality of any lossy compression is partly determined by how well it is able to hide this noise. MP3 is very good at this, a wonder given the fact that this codec is over 20 years old. You can also see that the quantization noise floor is shaped according to the Equal-Loudness contour (Fig. I). It is fairly low at 4,000 Hz (I failed to point this out with my red line) and rises slightly towards higher frequencies.

Disadvantages of ATRAC compared to MP3

Fig. IV: Multitone signal, -6 dB, ATRAC 4.0, 24/44.1 (linear scale, Hanning)

ATRAC (in this case 4.0; DSP Type-R doesn´t differ) performs much worse. Quantization noise is stronger (70 dB, Fig. IV, MP3: -90 dB)... WideBitStream my ass! ATRAC has a datarate of 292 kBit/s to its disposal, the MP3 example has even less (256 kBit/s), yet it yields superior performance. But it should be clear by now that ATRAC also follows the Equal-Loudness contour (Fig. I), just like every other lossy codec. However, ATRAC & MP3 do a bit more: they completely remove high frequencies. MP3 did it in my example at 19 kHz, ATRAC at 17.5 kHz. They get rid of those frequencies because A) we don´t hear them well and B) because their encoding hurts the rest of the frequency spectrum. How can the presence of high frequencies distort frequencies below them? Because both codecs use a constant bit-rate, they cannot adapt this bit-rate (and therefore possible quality) to changing complexity patterns. MP3 is of course able to encode with variable bit-rate (VBR). But I used constant bit-rate only (CBR) to create fair comparison conditions. ATRAC is forced to encode everything with 292 kBit/s, no matter what. Should a certain signal require a higher bit-rate, pity, ATRAC simply can´t do it and has to take away more information at other areas, informations it might want to keep instead.

Advantages of ATRAC compared to MP3

Fig. V: 1 kHz sine, MP3 (Lame, 256 kBit/s), 24/44.1 (logarithmic scale, Hanning)

Fig. VI: 1 kHz sine, ATRAC 4.0, 24/44.1 (logarithmic scale, Hanning)

The situation reverses with less complex signals. Fig. V and Fig. VI exhibit that ATRAC performs superior to MP3 with simple signals. Quantization noise is more evenly distributed, resolution of 20 bits is retained. Which means: the less complex a signal is, the better can it be encoded by a lossy codec; apparently, this is even more valid for ATRAC. But it has another advantage: its time/frequency resolution, expressed in block length. Perceptual codecs need to decide between long mode and short mode. The latter enables any lossy codec to encode transients (very short & loud signals, for example the attack of a piano or handclapping). For short mode, MP3 uses a window size of 192 samples (or 4.3 ms). Now if a signal is shorter than that it is ignored, it ceases to exist because it's effectively 'invisible'. In comparison ATRAC has not one but two short modes. For lower frequencies it´s 130 samples (2.9 ms), for higher frequencies 65 samples (or 1.45 ms). In general, ATRAC is better suited to encode very loud and short transients, helping dynamics and precision.

Sonic differences between ATRAC & MP3

Ask 'normal' people (not audiophiles) how they perceive the sound of MP3 and you´ll most likely receive the answer that it sounds slightly warmer to them, that is, if they can hear any difference at all. Yet your basic audiophile will call its sound 'cold' and 'digital' when in reality nothing could be further from the truth (their reasoning: it must sound that way because it uses lossy compression). Listen, all you audiophiles out there: MP3 encoded music sounds a tiny bit warmer compared to the original. The reason is not that it removes any frequency content above 16 kHz (also stated by audiophiles), the one and only true reason is that it fails at encoding short transients responsible for dynamics, attack and precision. When ATRAC still was used regularly it too was described as sounding 'cold' (for example in German STEREOPLAY magazine 15 years ago). Again, this isn´t true. At least not for ATRAC 4.0 and ATRAC 4.5. Both sound significantly more pleasant and warmer than the original (ATRAC DSP Type-R changed the situation somewhat). Responsible for this mellow signature isn´t a too short window size. These shortcomings are caused by the ATRAC codec attempting to encode signals up to 20 kHz. All those years ago, magazines and audiophiles alike (the german STEREO magazine paramount among them) constantly pressed Sony to improve rendering of high frequencies. They believed that if you could retain frequencies from 16 to 22.05 kHz it would yield true audiophile sound. Bullshit! ATRAC would have profited extremely if they wouldn´t have listened to audiophiles, I will show you how.

Tweaking ATRAC

Fig. VII: ATRAC standard encoding (24/44.1, linear scale)

By trying to encode signals up to 22,050 Hz (see Fig. VII) ATRAC is losing precious available bits better reserved for lower, more readily audible frequency bands. This creates an overall pleasant sound signature by producing soft compression artifacts. Of course, this sound is far away from the truth. The final critical band ATRAC encodes is the frequency area from 15,500 to 22,050 Hz, if it wouldn´t be present anymore, ATRAC would have more bits to spare for lower frequency bands (0 to 15,500 Hz). Remember: the less complex the music is (a.k.a. less frequency bands), the better will it be encoded by ATRAC. For that reason we will erase frequencies beyond 15,500 Hz with an equalizer so that ATRAC 4.0 or higher doesn´t need to concern itself with these frequencies anymore! Will this sound muffled? No, it won´t since ATRAC encodes transient responses with utter precision (compared to MP3 which always sounds slightly blanketed depending on the material). Getting rid of frequencies beyond 15,500 Hz improves quantization noise as a result:

Fig. VIII: Multitone signal, -6 dB, ATRAC 4.0, STANDARD ENCODING, 24/44.1 (linear scale, Hanning)

Fig. IX: Multitone signal, -6 dB, ATRAC 4.0, 15.5 kHz CUTOFF, 24/44.1 (linear scale, Hanning)

Look at Fig. IX and compare it to Fig. VIII by clicking on one of them with the left mouse button and scrolling through both of them. Quantization noise floor has been lowered by roughly 5 dB - and only because frequencies beyond 15,500 Hz have been removed. Stunning result, isn´t it?

Fig. X: RMAA frequency response, ATRAC 4.0 STANDARD ENCODING, four passes

Fig. XI: RMAA frequency response, ATRAC 4.0, 15.5 kHz CUTOFF, four passes

Even RMAA recognizes the effect. Fig. X & XI depict that the hole around 4,000 Hz, typical for any ATRAC version, has almost disappeared along with the odd response at subsonic frequencies (20 Hz). Increasing levels from 10,000 to 15,000 Hz on Fig. XI are caused by my equalizer setting (see below at 'Equalizing ATRAC (costly option)').

Equalizing ATRAC (free option)

I told you that this tweak is free, I therefore searched, found and measured a suitable equalizer. This was difficult, not many free equalizers around are able to process with high quality. I will however also tell you about costly alternatives, namely SoundForge and iZotope Ozone. SoundForge is the VST-host while Ozone is the equalizer I work with in that case. I will talk about them because they are yield slightly superior quality. Never, I repeat, NEVER use built-in equalizers (SoundForge, WaveLab, Adobe Audition, foobar2000, Winamp). I´ve measured them and they create so many errors that it´s shocking. Anyway, to achieve the tweak without paying any money while still retaining high quality you´ll need these things:

- foobar2000 (get it here)
- a VST-wrapper (get it here)
- the equalizer EngineersFilter from RS-MET (get it here)

or

- Audacity (get it here)
- the equalizer EngineersFilter from RS-Met 

Fig. XII: RS-MET EngineersFilter setting for ATRAC Cutoff

Fig. XII reveals my configuration for the cutoff filter. The EngineersFilter offers several other filtering methods but I decided to keep it simple in order for less tech-savy people to use it as well. Regarding installation/setup of foobar2000, its VST-Wrapper and the EngineersFilter I cannot help you however, you need to figure that out for yourself, the same goes for Audacity. Other recommendations are: keep the signal at 32 bit floating-point, regardless if you´re working with foobar2000, SoundForge or any other digital audio editor. As you know, the MiniDisc is capable of working with high resolution material so if you´re recording from a PC just keep it at that high resolution. If you don´t want to use a PC I´d recommend a CD-RW (which can be erased and rewritten). In that case, decrease bit-depth to 16 bit without using noise-shaped dither (the shaped and dithered quantization noise would otherwise confuse ATRAC again) and burn the results to CD-RW.

Equalizing ATRAC (costly option)

Fig. XIII: iZotope Ozone 4.0 settings for ATRAC cutoff

Fig. XIV: iZotope Ozone 4.0 general setup (-> click 'Option')

First of all you´ll need a digital audio editor like SoundForge, WaveLab, Adobe Audition or Audacity. With these you´ll be able to load iZotope Ozone (in my case, version 4.0) which you will configure to the specifications pictured in Figs. XIII & XIV. The 1.5 dB amplification of frequencies at 20,000 kHz is optional and used by me to fool my ear into not recognizing that certain frequencies are alltogether absent. Why would you even use the iZotope Ozone EQ? Because it´s in my experience the best equalizer on the market, it doesn´t create phase distortions nor other distortions or errors and generally performs perfectly. Have a look:

Fig. XV: iZotope Ozone, phase response

Fig. XVI: EngineersFilter, phase response

The phase response sadly is very underrepresented when it comes to sonic differences between DSPs or units playing audio material. In this case it´s evident that iZotope Ozone has superior phase performance (Fig. XV) compared to the EngineersFilter (Fig. XVI), yet it is debatable if this is audible at all. Let´s be fair: the EngineersFilter EQ performs admirably compared to all the other free EQs I´ve tested. Impulses play a role too:

Fig. XVII: iZotope Ozone, impulse response

Fig. XVIII: EngineersFilter, impulse response

Fig. XVII depicts a perfectly symmetrical impulse response for iZotope Ozone. A high steepness of the cutoff filter produces better frequency resolution at the expense of perfect impulse response. The same is true for the EngineersFilter, although here the impulse response (Fig. XVIII) is modeled after the first CD players with analogue anti-aliasing filtering. In the end you have to decide, I´ve written it years ago that the effects of impulses are overrated. BTW, the settings I´ve described yield the following measurable results:

Fig. XIX: frequency response, ATRAC 4.0, 15.5 kHz cutoff (logarithmic scale)

Fig. XX: frequency response detail, ATRAC 4.0, 15.5 kHz cutoff

As you can see on both examples above which were created by RMAA I´ve achieved the desired effect - without frequency deviations created by crappy equalizers and, almost (for the EngineersFilter) without phase distortions. The graph depicting the zoomed-in frequency response (Fig. XX) reveals a not too steep cutoff, yet it´s precise enough to get rid of frequencies beyond 15.5 kHz. The result of my procedure is evidenced by Fig. XXI: the picture shows a spectogram derived from an ATRAC encoded/decoded recording (compare to Fig. VII). The precise 15.5 kHz cutoff is clearly visible.

Fig. XXI: ATRAC encoding with 15.5 kHz cutoff (24/44.1, linear scale)

The sound

When I first heard the results I couldn´t believe my ears, the sound had improved by such a margin that I was wondering how I had been able to listen to it before. Precision, attack, stability and holographic impression of the stage were sounding so much better now... But listen for yourself. The following files were recorded digitally with the Sony MZ-R 55 featuring A) the standard full-frequency and B) the 15.5 kHz cutoff discovered by me. In both cases, the original files were at 24/44.1. After recording I played them back using the Kenwood DM-5090 (also digitally) and recorded its output with the optical input of my Creative Labs Soundblaster X-Fi HD USB. After that I merged three 30-seconds examples and uploaded them to soundcloud. INSTEAD OF LISTENING TO THEM ONLINE, DOWNLOAD THEM! Reason: both are ATRAC-encoded/decoded PCM-files, encoded again with MP3 by soundcloud (at 128 kBit/s). Should you just press 'play' you´d only hear a transcoded file, revealing compression artifacts clouding possible differences. Downloading them however you´ll be able to listen to the pure, ATRAC-encoded/decoded, Kenwood-derived, digital files in pristine 24 bit quality without further influence from soundcloud. You would even be able, should you desire, to perform a DBT listening test; these two examples were edited with sample precision.

Three ATRAC 4.0 encoded samples, standard encoding

Three ATRAC 4.0 encoded samples, encoded using my 15.5 kHz cutoff filter

Epilogue

And? What do you say? I feel that the result speaks for itself. I admit that this tweak requires some effort but I think that it´s worth it. I now can use ATRAC 4.0 again! Oh yes, I almost forgot... why didn´t I use a more recent ATRAC version? While the effects will be superior using ATRAC 4.5 or higher, the ATRAC 4.0 equipped recorders I own (MZ-R 30, MZ-R 50, MZ-R 35, MZ-R 37, MZ-R 55) have high quality drives, producing MiniDiscs running without flaw on any other MD recorder / player. Later units (MZ-R 900, MZ-R 909) featuring superior ATRAC ICs fail to do this. With the exception of the Sony MZ-N 510 they all record with unreliable results. I also admit that it isn´t very convenient to use MiniDisc these days. The reason to use them, for me at least, isn´t their sound. Every other lossy codec employed today around the world is superior. I´m sorry, but it´s a fact. Still, I love those little discs. The players/recorders are of high build quality, sound well enough (in some cases more than well) and you get the joy of bringing some amount of 'slowness' into your musical life by occupying yourself with media you can actually touch. Let´s face it, I´m an idiot. An idiot... just like people still listening to vinyl. Like them I believe in an ancient and deceased format. But have I mentionend yet, that it´s pure joy? Oh, I did? Never mind! Anyway, with my tweak you´re able to prolong the lifetime of MiniDisc before it´s completely replaced by superior codecs and playback devices. And while you´re at it, use it in combination with the FiiO E07K, it´ll sound even better this way. Use this chance well and enjoy the results!

Last update: 06.09.2013