Monday 25 February 2013

MEASUREMENTS: Asus XONAR Essence One [Updated June 25, 2013]

As I indicated in the E-MU 0404USB page, this is my new workstation DAC. The measurement setup is somewhat different but I will use the 040USB done on the workstation itself rather than the laptop I used in the previous page:
- Computer: Intel i7-3770K @ 4GHz, 24GB DDR3, ASrock Extreme 4 motherboard
- E-MU 0404USB --> USB2 of the computer motherboard using generic USB cables. E-MU located about 3 feet from the main computer (too close results in obvious RF interference raising noise floor).
- For unbalanced testing: RCA (3ft, Radio Shack shielded cables ~$10) --> XLR adaptors (maybe $25 for the set)
- For balanced testing: "Monoprice" brand XLR's bought at pro music shop years back
- The electrical outlet to the gear is provided by a Belkin 10-head surge protected power strip connected to my CyberPower 1500PFCLCD UPS which protects my computer. No fancy powerline filter needed to get these results :-)

ASUS XONAR Essence 1 (slightly modified with NE5532 6 opamps replaced with LM4562's)
- Internal DAC chip: dual TI/BB PCM1795's
- Using current latest driver / firmware: / 0111 / MCU 1.27

A few observations: Well made DAC. Asynchronous USB interface with the CM6631 receiver. Likely much more expensive if it came from some boutique audio brand. Heavier and larger than I expected! Should be a good test of the approx limits of the E-MU as testing gear. The upsampling certainly does something to the sound and so far, I'm not a fan of what it does...  Let's have a good look at it later on.

Here's what a 1kHz square wave at 24/44, 0dBFS off the RCA jacks looks like under the oscilloscope (oversampling off). Overall the waveform looks good. However there's some channel imbalance with the right (yellow) channel slightly stronger by about 80mV.

16/44 impulse response. Absolute phase maintained, linear phase digital filter.

24/96 signal:
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The first 2 columns are the result between using the RCA vs. XLR cables. Clearly XLR is the way to go with 5dB improvement in noise floor, dynamic range, and stereo crosstalk. Bottom line, XLR buys you about 1-bit in digital resolution according to my setup with the Essence 1.

The last 2 columns are with the computer running full load (hence the note "NOISY i7"). I was running the machine full tilt with Prime95 and the graphics card inside (nVidia GTX 570) doing the "Furry Cube" demo/bechmark from GPU Caps Viewer. Notice how the RCA unbalanced setup resulted in significantly increased noise floor by 14dB (about loss of 2 bits resolution)! XLR setup however ran stably with no evidence of the noise pollution.

Frequency response:

No major issue since we're looking at -1dB attenuation at 30kHz. However, compared to other DAC's I've tested, the drop off does seem steeper than I had expected. (I'll speak more about frequency response issues later).

Noise floor:

Clearly the "RCA NOISY" spectrum (cyan) is much inferior to the others. However, the RCA "quiet i7" (white) has a number of spikes evident including a -115dB hump at the 60Hz powerline frequency (IMO this is inaudible at normal volumes).

THD Graph:

Again, as above, the RCA output shows electrical noise pollution. Remember though this is essentially a worse case scenario with the CPU & GPU running 100% full tilt which should never be the case if you're trying to listen to hi-fi music!

Jitter (J-Test) Analysis (24/48, RCA output):
Using the 24/48 signal and my usual analysis with WaveSpectra, this is what it looks like with upsampling disabled:

That's pretty good. The occasional spike down at about -120dB below the peak, sideband well controlled. I doubt this level of jitter would ever be audible with human ears as a test signal and IMO impossible with actual music.

Some audiophiles have this belief that computer load somehow affects jitter so they will run massively stripped down OS'es because supposedly it improves jitter by reducing unnecessary processes... Here's what it looks like with Prime95 running the CPU 100% and at the same time I'm straining my nVidia GTX570 with FurMark:

There's now a "bump" down at 8-9kHz range, about 110dB below the 12kHz peak. Looks like electrical noise; not jitter. If this is all that happens with a large unrealistic load (100% CPU and 100% GPU load ain't something you'd likely ever do while trying to enjoy high quality audio!), I say don't waste time stripping down the OS!

With upsampling turned on:
Pretty much like the standard jitter FFT above, no change whether upsampling on or not. At least for the Essence One, no evidence that upsampling helps reduce jitter.

Upsampling 'Feature':
As I mentioned at the beginning, the upsampling "feature" currently doesn't sound right to me. It just seems to dull the sound and take out the usual sparkle in music. Here is why at 44kHz:

No matter which input selected - USB, coaxial, TosLink - activating the upsampling feature (front button) results in quite a nasty lowpass BELOW 15kHz!  This is clearly audible to most young people and probably to a number of older audiophiles :-). ASUS, what's going on here?!

The situation is better at 24/96, but you still see a premature high frequency drop off:
Finally, here's 24/192:
No difference between standard and upsampling turned on! But they BOTH drop off together down to -5dB by 50kHz.

So far, I have not seen ASUS respond to this and I can only assume that at least in the case of 44kHz, there is some kind of BUG in the firmware causing this issue since that 15kHz drop off is quite noticeable. Although not perceptible, the high frequency roll off at 96 and 192 kHz sampling rates also seems a bit premature compared to other DAC's I've tested.

Here's the impulse response with the upsampling turned on:
Basically what they did with introducing an earlier roll-off is to reduce the pre- and post-ringing on the impulse response...  I assume the above is intentional. Seriously, not a reasonable price to pay for the loss of the high frequencies!

Subjectively, I like how the Essence One (upsampling OFF) sounds - nice and clean, detailed, good rendering of dynamics... It certainly has the oomph to drive my AKG Q701 headphones (compared to the E-MU 0404USB) and the Sennheiser HD800 has never been this detailed. The dual volume controls (main speaker out + headphone) was a major reason I bought this for my computer workstation listening. Drivers are also much less buggy than the E-MU and the ASIO works well without any issues switching back and forth between sampling rates.

If you can, I highly encourage use of the balanced XLR output. With my testing setup, the XLR proved to be resilient to electrical noise and lowered the noise floor by around 5dB (not likely audible but nice to know!).

BUT, I cannot recommend this DAC wholeheartedly until they fix that really strange frequency response issue with 44kHz sampling rate and upsampling. Strange that ASUS would hype up the "symmetrical upsampling" as a feature but in reality IMO noticeably worsening the fidelity when you turn it on!  I also don't know why there's a premature roll off at 96kHz and 192kHz even when the upsampling algorithm isn't activated...  It'll be nice to hear an official response from ASUS about this - is this intentional!?

Other than some astute comments I've seen on message boards, it's interesting that most 'official' reviewers have not mentioned this rather obvious anomaly.

If you guys are looking into this frequency response issue with upsampling, why not just implement a minimum phase filter with slow roll off from about 18kHz for the 44/48kHz sampling rates? This is of course a bit of what the big boys like Esoteric, Ayre and Meridian have been doing over the years. 

That would be something many of us can conceivably use and potentially beneficial from the sound quality perspective (lets turn this defect into something potentially good!). It should be quite easy to implement with the SHARC DSP - open source software like SOX can easily do this already for years...

In fact, all my 16/44 music is minimal phase upsampled to 24/88 on the server side when I listen to the Transporter to get rid of that pre-ringing...

Default Transporter impulse response:
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SOX minimum phase "apodizing" 16/44 --> 24/88 on Transporter:
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  1. Hi!

    I also became aware of the low freq. issue with "upsampling" and have got in contact with ASUS support. After some mails back and forth I gave up.

    I you look at the Main PCB inside, close to the Analog Device DSP there is a 8pin DIP that properly has the DSP code. I dont think ASUS is able to make a Firmware update to the DSP code.. that is very sad! How old was your unit that you testet ? Mine is one of the first that came on the market in EU 1+ year ago.

    I wonder if the newer Essence ONE: MUSE and PLUS edition has a updated DSP code ?

  2. Hi BachAudio,
    I bought the E1 in late November 2012, so not one of the early releases.

    I posted my concerns on the headfi forums here:

    An ASUS rep that goes by the moniker "ASUSXONAR" posts there and states that a firmware update should be able to fix this and that all models should benefit from the firmware upgrade... They're "looking into this". Claims the upsampling algorithm currently used biases higher sample rates (88kHz and up) hence the steep filtering effect - I have no idea why anyone would care to upsample hi-res!

    I look forward to one day updating this entry with graphs of decent frequency response curves with the ASUS Essence One upsampling turned on!

    1. Hi Archimago,

      Thank you for your insights and link. It sounds promising if Asus can fix the DSP filters by firmware update in some upcoming rel. :) But I still have my doubts if they can change the DSP firmware code.

      I notice that on the forum there are some pictures of the main PCB of E1 with some jumpers that set gain in the Headphone section. My version do not have these jumpers, so Asus must have made an updated revision of the main PCB compare to my early version.

      By the way I have been using a passive I/V circuit for about 6 month now, and to my conviction this sounds better than any opamps that i have tried. I have posted a few details about this on the forum, to hear if there is some one interested in a passive drop in PCB.

      The PCB is not fabricated yet, as I would like to know if there is interest in trying.

      Maybe you could do a review with passive I/V on your Asus Essence One ?

      Flemming Bach

    2. Sounds neat BachAudio!
      I see your posts over on head-fi. Nice and will certainly follow along... Love to give it a try as well when fab'ed.

      I sure hope the DSP code can be fixed from ASUS!

  3. Thanks for making these measurements. Someone (maybe you) tipped me about this post in the comments on my overview video on Youtube for this device.

    I currently own two units and have bought quite a few opamps. The plan is to swap opamps in one unit and give some subjective opinions on the different qualities by doing back to back listening. It would be nice if I could use some of your material in the video (and of course give you cred for the work, and link to this article). Are you OK with this?

    Also thinking about writing ASUS to let them know what I'm going to do. Maybe they will look further into it if enough of us write them to let them know we're not thrilled with this? What department did you write when addressing these issues, please?

    1. Hello HPA,
      By all means, happy to share the data! :-)

      I haven't directly contacted ASUS other than through the ASUSXONAR rep. in the above head-fi forum discussion. I also posted a message on the ASUS support forum (which I can't seem to find anymore).

      Hopefully the general viewership and posts like yours will help encourage ASUS to fix this defect.

      Enjoy the opamp rolling and let me know of your final impression!

    2. Hi, and sorry for the late reply. Thank you for letting me use your data. :)

      I've contacted ASUS through their technical support ticket system. Basically told them what I was intending on doing, referring to your data and that I wanted some official statement from them about the issue.

      Their reply:
      "I am investigating this report, however at this point i do not have any answer or comment to give to the issue other then that we are looking into it.

      It might take a while before I get information, so please be patient."

      We can always hope they'll do something about it. It has only been 5 days since I received their reply. Will come back and let you know what they're saying.

      HPA (nice new acronym for me there, haha)

    3. Thanks for the update HPA.

      I also issued a "Technical Inquiry". Body of the request:

      "[Problem Description]
      Essence One "upsampling" feature has very poor frequency response with standard 16-bit/44kHz data.

      Fully documented on my blog post:

      Please issue new firmware to correct the DSP algorithm to improve standard 16/44 upsampling.

      Thank you."

      I heard ASUS might be releasing a new XONAR DAC/amp combo soon. Hopefully they can get around to firmware upgrade as well.

  4. Upsampling seems useless anyway. The DAC (digital->analog) process is an 'upsampling' of sorts, it changes discrete signal to continuous. Why bother with another step in the middle changing one form of discrete to another form of discrete (with more points that don't add information that isn't there in the original file!) before changing to analog (continuous)?

    Also minimum phase doesn't seem a good choice. It destroys the phase info

    1. Agree.

      I don't actually think upsampling is necessarily an important or even 'useful' feature. However, some folks feel removing that pre-ringing is a good thing...

      I guess my position is that IF ASUS wants to make a potentially useful upsampling algorithm, then might as well do something like this and let the listening have a choice.

      As it stands, the bizarre roll-off in the audible spectrum just doesn't seem to make sense.

  5. Can anyone give me an opinion on how it is compared to Audiolab M-Dac? My setup is PC to DAC to Active speakers(Monkey Banana turbo 5), Headphones on occasions. I am no experts and I am debating which one I should go for. Thanks~!

  6. Somehow after trying many headphone amps (and integrated amps with headphone jacks) I purchased the Essence One Muses Ed. on a whim. Well, not exactly a whim - I read some reviews (typical flowery prose stuff) saw the pictures of the PCB and component/build quality and decided that it looked well engineered, comes from a company known for quality, and a company hungry to break into a new market (think Lexus in the early 1990's). This was enough for me to give it a go. I'm so glad I did too - the E1 is the first headamp that has actually exceeded my expectations. I think my HD800's have never sounded better - and yes, I also use a Squeezebox Touch as a transport :) Do you have any plans to measure the E1's headphone output? I know it uses a LME49600, but specs I have found are not super helpful. Any personal thoughts on "opamp rolling?" I'm a skeptic myself but I figured that for well under $1000 I might as well get the Muses Edition since it's a relative bargain compared to the Benchmark DAC1 USB, Grace M903, Violectric V800/200, etc. (and honestly, I much prefer the big "crouching tiger" logo on top to be low-key black rather than bold gold). I'm really happy with this setup and have to admit I find it reassuring that you have the same chain, have measured and reported on it, and agree with my subjective opinion. Cheers!

    1. Yup, I agree, the E1 is an excellent unit for headphone use. I still use it for most of my workstation listening daily and has not disappointed me yet. The way I see it, the Essence One is meant to sit with the computer due to the dual independent volume controls versus something like the TEAC UD-501 which I see more as a DAC to use in the audio room.

      Although I have not objectively measured it, I do believe opamp rolling makes a difference. Years ago, I had an old Tianyun Zero DAC which I played around with replacing opamps from Linear Tech, LM4562's, OPA627's, and discreet Audio GD Earth HDAM. I thought some of the combinations caused subtle tonal changes. Yet to see anyone publish measurement results through the headphone amp or analogue output though so I'm certainly curious what difference the opamps make!

  7. I RMA'd my E1 Muses because mine had the channel imbalance and missing gain jumpers (early version?). I received my replacement 2 weeks ago and all is well now. However, Asus has not yet provided me with an RMA number or return address, so it's boxed up and sitting in my home office waiting for them to contact me. This got me wondering...if you are interested, maybe you would like to test my latest greatest "Muses Edition" next to your "Standard Edition?" This seems like a good opportunity for a follow-up article to examine any subjective and/or objective differences between the Muses and standard opamps. I can ship it to you, or if you're willing, I can drive up (I'm in Seattle) and give them a listen too. You can PM me on head-fi if you like...

    1. Oh man, that's an awesome offer!

      Unfortunately I'm about to head off to an Asia holiday for a month in August :-). In prep for that and work responsibilities, other than little tests here and there, I likely would not able to do justice to the E1.

      I'll certainly be open with any offers come September when I get back and get ready for the rainy days ahead, holed up in my man-cave :-).

      I'm glad you got one of the new Muses! Good to see ASUS making good on the early adopters.

    2. No hurry. Whenever you have time for a proper test and listen, just let me know and we'll schedule it. Have a great vacation!

  8. Does it exist an usb audio interface (ADC+DAC) with true 20bit resolution?

  9. I really enjoy your web site. Found it while researching my (now new) Mytek DAC and have been hooked ever since.

    I come from The Old Skool – i.e., what used to be called audiophilia. (Full Disclosure: I stopped self-identifying as an "audiophile" about 15 years ago. e.g., On my old Audio Asylum profile [whackamus], I'm even listed as an "audio enthusiast." Enthusiasts, in my experience, are a deviant lot.)

    I love the hell out of your practical, empirical, evidence-based approach to stuff. It isn't so much a breath of fresh air -- altho it's that, too -- as a vital, indeed, a _necessary_, corrective: an enema for audio enthusiasm! And -- to paraphrase Jack Nicholson's Joker -- if ever any town were in need of an enema, it's audiophile-dom.

    Question for you, however: I've never been able to hear pre-ringing. No never?! Okay: hardly ever! In a few cases, on a few recordings, I've heard what I take to be a pre-ringing-like effect, but (a) that hasn't been the case in years (I'm almost 40), and (b) it's by no means a widespread problem. Pre-ringing is nonetheless one of the chimerae/bogeymen about which audiophiles and their technical enablers have been obsessing for years. (A decade and a half, at least.) So I read this with interest:

    "In fact, all my 16/44 music is minimal phase upsampled to 24/88 on the server side when I listen to the Transporter to get rid of that pre-ringing..."

    Is that a Transporter-specific adaptation? Is its low-pass implementation that bad?! Or are you honestly sensitive to pre-ringing? If so, what am I missing? I know that you've touched (sometimes at length) on pre-ringing or ringing artifacts in your various postings, but I'd really appreciate a primer on what pre-ringing is and, more important, just how prevalent a problem it is. (I get what it is. Sort of. I mean, at an abstract level. I don't get why it's a problem for music -- or for _most_ music; for the _vast majority_ of music.) Is it more of a bogeyman or specter (like jitter) that audiophiles use to try to scare-the-shit-out-of/FUD-monger-with one another? Or is it more pervasive than I'd thought? You don't necessarily have to respond on here. You could drop me a line at [name-of-the-guy-who-built-the-labyrinth, without brackets, of course]

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  12. Hello! My Essence One puts out 3 quite loud "thumps" through the headphones when I switch it one and it cycles through the inputs during the startup sequence. Have you experienced anything like it? Is this normal`?

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  15. Just curious... Was the 44kHz issue ever fixed?

  16. Did you ever happen to measure the output impedance of the EONE? I do not find any real measurement for this on the whole interwebs....

    1. In case you're referring to headphone-out, then it's 10-ohms.

  17. Does somebody know if there are any significant changes to the MKII Muses Edition compared to the standard one? Thanks a lot.