Thursday, 7 August 2014

MEASUREMENTS: AudioQuest Dragonfly v1.2 Reviewed

An audiophile buddy of mine (AudioPhil) got married a few months back and a few of us decided to chip in to give him one of these Dragonfly DACs for being a good sport :-).

I don't think the Dragonfly requires much introduction since it has been around in the 1.0 iteration since 2012 and Stereophile had it grace their cover page with a full review back in September 2012. It uses an unspecified ESS Sabre DAC (not sure if confirmed, likely the ES9023 with integrated 2Vrms driver - there's also the older ES9022 chip) and the USB communication part is the TI TAS1020 performing asynchronous data transfer. I haven't read anywhere if these parts have changed in the 1.2 version. Supposedly, the new version has improved sonics ("Even smoother and more open sound!" seems to be the official tagline).


It looks good and feels great in the hand with a slight rubberised texture to the surface of what seems to be a metal shell underneath. As you can see above, it is slightly smaller than my AudioEngine D3 previously tested. Despite the smaller size, the weight on the Dragonfly feels heavier; hence a noticeable ruggedness and density to the package. It comes with a small black pouch for safe keeping along with the USB cap. I don't think the Dragonfly comes with a 1/4"-to-3.5mm adapter cable like the D3.

You can see the Dragonfly indicator change color depending on sample rate. AKG Q701 connected.
In use, I found that it didn't get too warm and was clearly cooler to the touch after about an hour of listening compared to the D3. AudioEngine was quite open about revealing the use of the LME49726 op-amp for the headphone output and presumably the Dragonfly utilizes the integrated op-amp function of the ES9023 (or similar chip) as per the "direct-coupled circuitry" in their promo material. From a price perspective, both the AudioEngine D3 and Dragonfly are priced similarly, $150CAD for the Dragonfly and $170CAD for the AudioEngine D3.

Other specs like output impedance (12 ohms Dragonfly, 10 ohms D3) and power (150mW Dragonfly, 200mW D3), both being driverless USB Audio 1.1 devices with a maximum of 24/96 sample rate (it is capable of the important 88kHz for DSD conversions) further adds to the functional similarities between the D3 and Dragonfly. These driverless USB DACs make it really easy to just "plug 'n play" with Windows and Mac OS X - I did not try using Linux but that should not be a problem.

I. Objective Evaluation

A. The Basics
As you may recall, at 100% volume, the AudioEngine D3 would clip. This was noted to happen with the Dragonfly v1.0 as well; discussed in the Stereophile measurements, and used to show some atrocious distortion numbers by Light Harmonic when they did their "Geek Out vs. the Others, 3rd Installment" (5% THD+N!? Sorry, that's just plain nasty and paints the situation in a much poorer light than it should even though objectively correct...). Well, it looks like this issue has been resolved with v1.2; here's the oscilloscope measurement from the unit I have on hand:
Square wave at 0dBFS.
Sine wave at 0dBFS. No clipping at 100% volume.
Peak volume of 2.63V correlates with an RMS voltage of 1.86V. Hmmm... I suspect this must be what they did to avoid clipping if the ESS chip used is the ES9023 with 2Vrms capability; dropped the highest volume level settings (notice that the Geek Out test posted was with 100% volume at 2Vrms).

There is bit of channel imbalance in the graphs above... It represents approximately a 0.5dB difference (left channel louder) at full 100% volume.

Impulse response is the typical symmetrical appearance of a linear phase oversampling filter. The signal maintains absolute polarity. No surprise.

B. RightMark 6.4.0
Okay, with the above done, let's have a look at the resolution of this DAC using the RightMark test bench. Like with the AudioEngine D3 tests, this was performed with the latest free version using the ASIO device interface.

Setup:

Test machine + AudioQuest Dragonfly --> shielded phono-to-RCA cable --> E-MU 0404USB --> shielded USB --> Win 7 laptop running RightMark 6.4.0

Summary of the machines tested (the laptops were described here in more detail although OS has been updated):

1. ASUS Taichi 21 Ultrabook (early 2013): Intel "Ivy Bridge" i5-3317U (1.7GHz dual), 4GB, Windows 8.1 x64, 128GB mSATA SSD, USB3 port, foobar + WASAPI component 

2. Apple MacBook Pro, 15" (mid 2009): Intel Core 2 Duo (2.26GHz dual), 8GB, OS X 10.9.2 "Mavericks", USB2 port, WD 640GB SATA HD, Decibel player (AIFF files)

As you may recall when I tested the AudioEngine D3, I measured that device with 6 different machines! It was clear that this made no difference to the measured audio output (and I heard no difference either - indeed folks, bit-perfect does mean something)... For these tests, I just chose a PC platform and a Mac platform, both are laptops, but with major differences like OS, file types (FLAC vs. AIFF), different generation Intel CPU, different player software, USB2 (Mac) and USB3 (PC).

Let's start with the 16/44 standard resolution (CD-quality) signal:

The 2 columns on the left are the measurements from the Dragonfly 1.2 - leftmost using the ASUS Taichi laptop, second one using the MacBook Pro. The middle column is the result from the AudioEngine D3 connected to the ASUS Taichi (exact same cables and setup as the leftmost column measured the same day), and the last two on the right are with my higher end DACs - the Transporter using XLR connection, and the TEAC UD-501 with XLR output measured awhile back. Note that because the AudioEngine D3 clips at 100% volume, the measurements were done at 91% which approximated the same maximum output voltage as the Dragonfly.

As you can see, when it comes to noise level and dynamic range, all these DACs are capable of ideal 16-bit resolution. Very low noise floors all around. Where things do seem to separate out is in the area of distortion - the Dragonfly appears higher in this respect compared to the others (repeated this a number of times to double check). Also, the stereo crosstalk is objectively higher with the Dragonfly. Here are a few of the graphs off RightMark:
Frequency Response - Transporter seems to roll off a wee bit more.

Noise floor.

Dynamic Range test.

IMD+N

Stereo crosstalk - note the significant difference between the Dragonfly vs. the others.
Now, let us look at the 24/96 (high-resolution) results:

The columns are arranged the same as above. Leftmost two columns represent the Dragonfly results, then AudioEngine D3, then the Transporter (XLR), and finally TEAC UD-501 (XLR).

Again, no difference in results between using the ASUS Taichi and MacBook Pro laptops despite disparate hardware and OS. The Dragonfly is indeed capable of >16-bit dynamic range, and at approximately 106dB, that's about 17.5-bits (same as what Stereophile found with their v1.0 review). As with 16/44 above, however, when you look at the measurements of distortion, the AudioEngine D3 is capable of less distortion and dynamic range is about 0.5-bits higher. Needless to say, the stand-alone "higher end" DACs like the Transporter and TEAC UD-501 with XLR outputs handily beat these little USB DACs by about another 'bit' of dynamic range and lower noise floor (especially the old Transporter!) measurable within the limits of my ADC set-up of course.

Frequency Response (no significant difference <20kHz)
Noise level - notice Dragonfly slightly higher especially in the bass.
IMD+N
Stereo Crosstalk - Dragonfly again significantly higher crosstalk... Very impressed by the Transporter using XLR cables! 
C. Jitter
As usual, I'll use the Dunn J-Test paradigm. Easy enough to do...


As in previous tests, with these asynchronous USB DACs, the Dunn J-Test spectrum generally looks fine. This is the situation here, no evidence of jitter issue at all using this simple measurement... Only very slight noise floor differences between the two laptop machines.

II. Subjective Evaluation

So I asked my buddy AudioPhil (the guy who actually owns this Dragonfly) to provide his subjective review and it looks like he'll be providing a little write-up of his own in the next while... While that's in "gestation", I figure I'll jot down a few of my subjective impressions and comparisons on this little device.

I spent about 2 weeks listening to music with this DAC/amp (some before, and some after the objective testing) and comparing what I heard with the same tunes off the AudioEngine D3 and ASUS Xonar Essence One (which remains my primary DAC on the computer workstation). Each of the devices have quite different DAC architectures; Dragonfly with the ESS Sabre, D3 with an Asahi Kasei AK4396, and the larger Essence One using TI/Burr Brown PCM1795s (quite unfair comparison given that it's not a simple USB bus powered device!). It's impossible to "instantaneously" switch headphones / DACs and then level-match compare... I tried my best.

A potpourri of DACs and headphones: AudioEngine D3, AudioQuest Dragonfly 1.2, ASUS Xonar Essence One; Sennheiser HD800, AKG Q701, Etymotic ER-4B IEM.
The published output impedances for the Dragonfly and D3 are around 10-ohms - the Essence One apparently has similar output impedance as noted by 'Xnoreq' in the comments although there are estimate of it being in the single digits [I'll need to have a look at this later]. So, to give them all a fair chance, I'll speak about what I heard using the Sennheiser HD800 (300-ohm input impedance) headphones primarily. Thankfully the HD800s have high enough sensitivity (102dB at 1Vrms) so music could be played reasonably loudly with the Dragonfly and D3 even with the lower power ratings. Of course from a price point perspective, the HD800 isn't the kind of headphone one would expect to see mated to an inexpensive USB DAC like this!

I started with listening to some "vocal audiophile jazz" - Diana Krall's The Look Of Love (2003 24/96 DVD-A) being one of my favourites over the years and particularly "Let's Fall In Love" as a track I've been using to compare new gear with since around 2000. I like the instrumental portion in the middle of the track and particularly the detailed resolution of the bass and piano through that portion. With the Dragonfly, the piano sounded rich and full. The bass was detailed with each pluck easily discerned. In comparison to the D3, the Dragonfly sounds more laid back and "smoother". The D3 just seemed to have a bit more sparkle, slightly brighter; for example the high-hats on the song stood out a bit more from the rest of the instruments. Personally, with my "Anaxilus mod" Sennheiser HD800, I preferred the D3 rendition but I can imagine with even brighter headphones, the Dragonfly may be preferred.

While staying with the vocal genre, I listened to some Nat King Cole - Cole EspaƱol (HDTracks 24/96 release, and no, I don't actually believe this album has enough resolution to warrant the high-resolution format). On a track like "Quizas, Quizas, Quizas", the Dragonfly was a joy to listen to with the HD800! This old 1958 recording can be a bit "brittle" through many DACs and the Dragonfly just made the instruments sound less harsh and the voice "ultra-smooth". I found the same on some traditional Chinese erhu recordings where the pleasant demeanor of the Dragonfly helped impart an enjoyable, smoother experience.

Time for some heavier fare - how about AC/DC Back In Black (1988 DR12 CD)? Pump this baby up to rock! The intro to track 1 - "Hells Bells" - with those church (er... hell's?) bells sounded realistic in terms of the attack and smooth decay using the Dragonfly. While not exactly the paragon of audiophile recording technique, this analogue recording from 1980 is about as "hard" as I like my rock to be and the Dragonfly was able to render it nicely. However, I found the Dragonfly to be a bit more on the "polite" side of things as compared to the more aggressive sound of the D3 which I thought fits this type of music better.

I listened to a number of other genres to get a feel for things - Pet Shop Boys Actually (2001 remaster), Yello Touch Yello (2009), Eiji Oue & Minnesota Orchestra Stravinsky: Song Of The Nightingale, Firebird, Rite Of Spring (1996 Reference Recordings), Ed Sheeran x (2014). In general, I thought that the Dragonfly performed well but was more at home with an acoustic set than say the synthpop or electric guitar rock. Despite the dynamic range compression especially near the end of the song, a track such as Ed Sheeran's "I See Fire" with overlaid vocals and relatively simple instrumentation found on x sounded just fantastic through the HD800 with the Dragonfly; bass response on that track was simply cavernous in depth.

Not unexpectedly, the much larger (and unportable) ASUS Xonar Essence One sounded better than the USB stick DACs. This has more to do with the quality of the headphone amp than the actual DAC function I believe - providing a more full-bodied, powerful sound overall (even more cavernous bass at the end on "I See Fire"!).

Near the end of my subjective evaluation, I put on some mono music to see if I could easily detect the channel imbalance noted above. For this I used the mono Beatles remasters from 2009. I listened to most of the Revolver and Sgt. Pepper's Lonely Hearts Club Band albums one evening. On the whole the stereo imbalance at normal listening levels with the Etymotic ER-4B balanced armature IEM (100-ohm impedance, excellent noise isolation) was subtle when I compared it with the output from the D3. I was concerned about perceptual bias knowing the objective results earlier so I asked my wife and she identified correctly the slightly louder left channel after listening for a bit. So, we're looking at a small, but perceptible imbalance.

III. Summary / Conclusions

There you go, the objective and subjective evaluation of the AudioQuest Dragonfly v1.2. Overall, from an objective perspective, it doesn't measure as well as the AudioEngine D3. The Dragonfly's 24-bit dynamic range is lower by about 0.5-bits in comparison, plus harmonic and intermodulation distortions measure higher. Furthermore, there's a bit more stereo crosstalk with the Dragonfly. Realize of course we're looking at tiny differences in terms of real-world audibility. For example, what audible difference is there between 0.011% THD (Dragonfly) versus 0.0009% (D3)? Would our headphones/speakers be able to manage such low level of distortion or our ears capable of such resolution? Remember that a typical NOS DAC like the old TDA1543 measures 5-10 times higher in terms of THD and IMD yet they can still sound OK (and in fact some audiophiles swear by them). The other difference was increased stereo crosstalk with the Dragonfly measured around -72dB. Compared to the others around -90dB or less, this sounds like a lot. Again, remember that a typical LP cartridge has "only" about 25-40dB channel separation at 1kHz. Therefore, again it's unlikely you're going to notice an audible problem.

The one area of concern for me was the channel imbalance on objective testing at 0dBFS on the oscilloscope with this unit. Even so, it was difficult to detect a difference at normal listening levels through my Sennheiser HD800 and AKG Q701 playing stereo music but could be detected with mono recordings using the Etymotic ER-4B IEM. This could really be a problem if one's headphones also had a slightly louder left channel imbalance issue. Perhaps others can double check if this imbalance is present with their own Dragonfly units.

I cannot help but suspect that the advertised "direct-coupled circuitry" where the op-amp is integrated into the ESS Sabre chip might be the reason for the relatively poorer objective test results. Compact size is achieved with this kind of arrangement but physical factors like significantly higher heat production could I suspect limit absolute sound quality from the DAC chip itself. I don't know if AudioQuest could have also "tweaked" the settings for the DAC chip to bias towards a more pleasant sound.

Here's the bottom line... If you're looking at the AudioEngine D3 versus Dragonfly v1.2 and want the best objectively accurate sound quality, go for the AudioEngine D3. It measures and sounds like a much more expensive separate DAC on a stick! However, the main caveat is that it clips at 100%, so keep it around a maximum of 92% and you'll hear some really clean audio. Remember what I also said previously about allowing a portable device to clip - it may not be an unreasonable trade-off when you just need that extra bit of volume in a noisy environment where a little distortion is fine. The D3 is also a little bit more expensive around here currently (only talking about $20 difference).

On the other hand, the Dragonfly is built very well and I would rate the look and feel of the unit higher than the D3. The color-changing dragonfly indicator based on sample rate is also a nice touch. Furthermore, it is slightly smaller and significantly cooler to the touch than the D3 after an hour of music being pumped through. Output impedance isn't much different between the two (both around 10-12 ohms), so check if you have higher impedance headphones (80+ohms) for best performance. The D3 can play a bit louder but remember this is with the potential for clipping at 100% volume. My usual benchmark for a "good enough" headphone amp is one where I would not need to put the volume to 100% to enjoy my AKG Q701s... And the Dragonfly is clearly good enough in this respect for what I listen to.

The main criticism I have of the Dragonfly is that ~0.5dB channel imbalance I found which I hope is just variability among samples rather than a systemic finding (remember that even well regarded cartridges for vinyl playback can have stated channel variances up to 2dB). Subjectively I thought the Dragonfly imparted a "pleasantness" to the presentation rather than aim for absolute technical precision as demonstrated objectively. Compared to the typical headphone jack on a laptop, it'll provide your headphones with more power, lower noise floor, and more dynamic range especially for 24-bit audio. I'd be very curious to know what objective differences there are between a 1.0 and 1.2 version of the Dragonfly if AudioQuest claims that 1.2 sounds better (other than no clipping at 100% volume)...

---------------------

Happy listening everyone... Considering the 24-bit performance from the AudioEngine D3 and Dragonfly, consumer audio technology is clearly getting better, smaller, and more affordable!

Weather has been very nice here in Vancouver lately. Off to an Alaska cruise next week so hopefully there will be blue skies and maybe see a few whales along the way. Catch you all later...

10 comments:

  1. Thanks for an exhaustive review. Please do try for a review of the HRT Microstreamer. It is similarly priced and has similar specifications, except output impedance is much lower at 0.5 ohms. Maybe HRT can lend you a unit if you ask them. It will be interesting to see a comparison of these USB DACs.

    ReplyDelete
    Replies
    1. Interesting. I will look around to see if I can borrow a unit...

      Delete
  2. Essence One output impedance is more like 14 ohms.

    ReplyDelete
    Replies
    1. Thanks for the note xnoreq - I'll update this...

      Delete
  3. For the DIY'ers interested in finding out the output resistance of their headphone amp a small tutorial.

    It is quite easy to measure/calculate the output resistance of a HEADPHONE amplifier.
    All you need is an AC voltmeter (or accurate scope), a sinewave generator (or file with a sinewave) and a resistor that must be connected across the output signal of the amplifiers headphone-out.
    You will thus also need to have a headphone plug and some wires.

    First you measure the output voltage of the amplifier WITHOUT any load.
    A set output voltage around 1V to 2V is a good place to start.
    Lets call this 'Uopen'.
    Conditions are the signal must NOT clip and the AC voltmeter must be able to measure the used frequency.
    Measure between one of the channels (ring = right or tip = left) and common = ground = sleeve

    Without changing anything else attach a load resistor (NOT a headphone) with a low value of say 33 Ohm as a load across the output signal and measure the output Voltage UNDER load.
    Any resistor value between 15 and 47 Ohm will do.... let's call this resistor 'Rload'.
    A simple 0.25W resistor is already fine.
    ENSURE the output signal is not clipping.
    If the signal doesn't clip, note the output Voltage UNDER that load... lets call it 'Uload'.

    When the signal is clipping, dial down the output voltage (under load) till it doesn't clip any more and THEN remove the load resistor.
    Re-take the Uopen measurement, attach the resistor and measure the output voltage 'Uload'.

    Now you can calculate the output resistance of the amplifier (lets call it Rout) by using the following equation:
    Rout = Rload / (Uload / (Uopen - Uload ))

    ReplyDelete
    Replies
    1. Nice information as usual Solderdude!

      Delete
  4. Hi Archimago,

    Big thumbs up for this blog!!!

    I have just finished 3 weeks of reading every post on your site, and it feels like I struck gold!!!

    Nice to see a voice of common sense based on mesured parameters, science, and human perception.

    Your posts about bit perfect playback (software and hardware), compressed, lossless and hi-res formats, vinyl playback, DAC's, cables, jitter, importance of studio mastering and DR, etc etc) gave me a real perspective among the dark forests of mainstream media where I resided for many years (Whathifi, Trustedreviews, The absolute sound, Sound&Vision, AV forums and many more) and learned almost nothing.

    I see vinyl playback, multichannel and room acoustics coming as your topics of interest in the near future, and maybe, following the signal path, some measurements of amps and speakers could follow?

    I see one topic (still) not covered here, and that is bluetooth streaming using aptx codec. I have some questions to ask, so please advice where to post them.

    Keep the good job, thumbs up!!!

    With best rgds,
    Goran

    ReplyDelete
  5. Will AUDIOQUEST DRAGONFLY V1.2 drive Beyerdynamic DT 770 PRO 250 ohms Headphone?

    ReplyDelete
    Replies
    1. It will provide 2x 16mW into a DT770/250 what translates as 107dB max.

      When you listen to audiophile and well recorded music you can expect a DR between 10 and 15 meaning that an average SPL of 92dB to 97dB is possible at 1kHz.

      Unfortunately music also consists of bass frequencies which, due to Fletcher Munson's findings, are usually approx. 20dB louder.
      So when looking at average SPL in Phon we are talking about 72Phon to 77Phon which can be described as 'comfortable' to 'normal' listening levels.
      Bass heavy recordings will start to distort above 'normal' listening levels.

      Delete