ASUS Xonar Essence ST/STX soundcards

With all the current fuss about getting audio data from a computer to a standalone D/A processor via S/PDIF, USB, FireWire, WiFi, or Ethernet (footnote 1), it has been overlooked that the oldest way to get audio from a PC is to use a high-performance soundcard plugged into the host machine's motherboard. I remember how excited I was when I installed a Sound Blaster Pro 16 board in the 486-based Dell running Windows 3.1 that I was using in the early Clinton era, plugged its analog output into my high-end rig, and played back 16-bit/44.1kHz files.

The first truly high-end soundcard of which I was aware—that is, one that would record and play back data with a 24-bit word length and sample rates of up to 96kHz—was the CardDeluxe from Digital Sound Labs, which I reviewed in September 2000. Since then, RME and Lynx have come to dominate the high-end soundcard market (footnote 2), even as, in recent years, the most activity has taken place at the low end of the soundcard market, fueled by the needs of video gamers. So I thought I would write about a new entrant in this arena, the Xonar Essence, from ASUS, a Taiwanese maker of motherboards and chips. It costs just $199.99, or even less from online stores such as

There are many cards on offer in this sector—ESI's Juli@ (yes, that's how it's spelled) and M-Audio's Audiophile 192 both seem popular with budget-conscious audiophiles—but I was particularly attracted to the Xonar Essence because it is advertised as having a signal/noise ratio of 124dB, which is true high-end territory. It even comes packed with a typical set of measurements, taken with the same Audio Precision SYS2722 measuring system that I use.

Technical details
ASUS sent me both the Xonar Essence ST and Essence STX cards. They appear to be identical, other than the ST being configured to fit into a standard PCI slot on a legacy computer's motherboard, the STX conforming to the newer PCI Express standard. From here on, unless otherwise noted, my comments refer to both cards.

The Essence looks like any other soundcard, with one important difference: Its analog output circuitry is shielded by a grounded metal cover, this anodized black with a stylized image of a Chinese tiger printed in gold. The cover acts as a Faraday shield, preventing RF interference from contaminating the analog signals.

On the card's exterior is a vertical array of jacks. From top to bottom, on gold-plated RCAs, are the right and left analog line outputs, followed by the headphone output on a ¼" stereo phone jack. Below that, another ¼" stereo jack serves as both the line and microphone inputs, these selectable with the supplied Xonar Audio Center software. At the bottom is an RCA jack that provides a standard S/PDIF digital output capable of running at sample rates up to 192kHz. An optical S/PDIF driver is placed at the interior end of the jack, so that a TosLink cable can be used with an adapter, if that is preferred. There is no digital input.

The bottom section of the multilayer card carries the analog input circuitry, this based on a pair of R4580 low-noise dual–op-amp chips, followed by a pair of 5532 dual op-amps. These feed a Cirrus Logic CS5381, a 24-bit A/D converter chip capable of operating at sample rates up to 192kHz and offering a S/N ratio of 110dB. At the bottom right of the card are two ASUS-branded LSI chips that do all the audio data processing, including Dolby Digital decoding, Dolby Headphone and Dolby Virtual Speaker processing, and Dolby Pro-Logic II, as well as volume and various reverberation and equalizer functions. Above the larger chip is the power-supply section, featuring multiple voltage-regulator chips, a large number of Nichicon Fine Gold electrolytic capacitors, and two purple Sanyo OsCon caps. As well as the attention paid to the power supply, ASUS makes much of what they call "Hyper-grounding," which minimizes noise that might degrade the analog output signal.

A high-performance, two-channel, 24-bit D/A converter—a Burr-Brown PCM 1792, the same chip used in Musical Fidelity's V-DAC D/A processor—is sited to the left of the supply section, adjacent to a vertical metal shielding strip. The analog output stages lie to the left of this strip and are covered by the removable cover mentioned earlier. Under the cover are two separate output stages, one for the line outs, the other for headphones. The headphone driver is a Texas Instruments TPA6120A2 chip, a current-feedback design capable of sourcing 80mWpc into 600 ohms with very low distortion. The line-level output stage is based on a pair of JRC 2114D dual–op-amp chips (the 2114D is equivalent to the popular 5532 chip), followed by a pair of low-noise National LM 4562 dual op-amps. Although almost all the components used, other than the electrolytic caps, are surface-mount types, the four output-stage op-amp chips are socketed 8-pin types, to allow the owner to experiment with other pin-compatible chips.

I installed the Essence ST in an older PC running Windows XP with Service Pack 3, but for the STX, I bought a Shuttle PC (AMD Athlon 3.1GHz dual-core processor, 2GB RAM) running Vista Home Premium, which has a suitable PCI-Express slot. The advantage of the Shuttle PCs is that they are dead quiet acoustically, meaning that I could place the PC in my equipment rack and use short interconnects to the preamp. Installation of the Essence cards in both computers was straightforward; an important point about both cards is that they don't draw power from the PCI or PCI-E slot in the computer's motherboard. Instead, they have a hard-drive–type 4-pin socket that must be separately connected to the PC's power supply. That way, the analog circuitry benefits from being maximally isolated from the noisy ground on the PC's motherboard.

Footnote 1: For a primer on this subject, read my 2008 article.

Footnote 2: The original version of the Sooloos music server, reviewed by Jon Iverson in October 2008, used a high-quality RME Hammerfall HDSP 9632 PCI card for its analog output stage.

ASUSTeK Computer Inc.
US distributor: ASUS Computer International
44370 Nobel Drive
Fremont, CA 94538
(812) 282-2787

Xavier Xerxes's picture


Thanks for your review.  I would like to use the digital and analog output connections at the same time: digital for my home theater 5.1 experience and the analog to be connected to a 12-zone amplifier.


Is it possible that both digitial and analog output signals can work this way?



Andrei's picture

I am running two of these beasties.  One an ST and the other an STX.  For my part I have never had a problem with either playing resolutions of 44.1, 48, 96, & 192.  Sound quality was already good and took a giant leap forward when I upgraded the op-amps (a very cheap exercise).

Now the tricky subject of resolutions of 88.2 Khz and 176.4 Khz.  In fact there is a workaround.  If you have the free Audacity software it can be done.  Audacity is one of those freeware programs that are just outstanding.  What you do is this: (1) you simply load the track to be played.  (2) you play it back in Audacity.  So you do not use Foobar or MediaMonkey or Windows Media player or the like.  Now here is the curious thing: when using Audacity for playback it actually sounds better than even Foobar, my current favorite.  Audacity is a progarm for manipulating sound, rather than playback, but it naturally has a playback feature so you can hear the effects you have done.  What I think is happening is this:  Audacity rips the track into memory as some sort of wav format and hence the bit-rate / resolution is no longer relevant.

While I am on this subject: I found a small improvement by running a co-axial into a dedicated DAC.  This is not really necessary and hardly justifies the expense because the Xonar ST and STX already have excellent DACs.  The cost is a lot because you will need not only a better DAC but the cabling has to be good too.

Mirko's picture

Thanks for the great and informative review.  I bought this sound card with the intention of streaming spdif out to my pioneer 09tx so I could listen to high def FLAC on my stereo system.   I had no idea that the quality of the card actually makes a difference when using spdif out.  Which is contrary to what most people write about spdif.  Often you read that it doesn't matter and that bits are bits.  But i found this actually isn't the case.  If you don't believe me, try for yourself.  I thought I could live w/ my motherboards Realtek spdif out to my receiver and let the receiver  do the decoding.  But noticed that My realtek spdif sounded like crap!!! ESPECIALLY when comparing against the sound files the receiver decoded from usb or the ipod dock.  So I considered an external DAC, but I know that my receivers dac uses wolfson 8741 chip which Is already good. Anyway, after hooking up this asus bad boy, i was blown away by the worldly difference in sound that it made.  Setting the output on the card to PCM 192khz and I'm all set.  Mission accomplished.  But that's not all.  After comparing the analogue sound of the card, i was again, quite impressed...which one did i like better? My receiver to decode or the asus PCM chips?  i did A/B comparison with the asus doing the decoding versus the pioneer by running a long 1/4" jack and setting the volume level the same between the two.  Let me tell you, for 200 dollars, this asus card does a seriously good job providing a crisp clean and open analogue signal to your ears. I still prefer the my receivers dac by wolfson chips.  The sound is a little more smoother and less harsh to my's different but not better.   But I killed two birds with one stone on this one.  For two hundred dollars I got an excellent digital transport to my receiver, and high end audio analogue outs from my computer that are clear, clean an extremely quiet.  Very happy customer here.  To think that there are people out there running spdif from  crappy cards to thousand dollar external DACS is sad to me.  Maybe I'm wrong..anyway.  Awesome card.  Awesome buy.  Killer sound.  Makes me wonder if I would be able to discern the difference from this card and the essence one.  


Andrei's picture

Hi Mirko

I agree the sound quality is really good.  My other Source is a Cambridge Audio 650BD (not counting a turntable). Overall the Asus Xonar ST eclipses it by a tad.  The comparison is a bit tricky though because (i) I have upgraded the op-amps; (ii) the CA 650BD does play DVDA and SACD.  But on an Apples to Apples Comparison CD vs Flac at 16bit 44.1 Khz : the Asus Xonar card is a smidge better.  It becomes even better when I play flac files at 24bit and 48, 96, and 192 Khz.  On the other side the CA650BD is a bit better when playing DVDA and especially SACD.  The CA 650BD is not high-end to be sure but it is not bottom end either.  I think for 'spare change' the Asus Xonar cards are simply fabulous.  Why anyone would buy a Music Sever when they can have this card?

Initially I used the RCA connections direct to the AMP.  Then I tried SPDIF optical, and USB into an external DAC.  Finally I tried SPDIF coaxial into an external DAC.  USB was easilly the weakest and SPDIF via co-ax is easily the best sound quality.  The caveat is that you do need good cables.  


Andrei's picture

Oops.  Ignore the USB comment above.  I actually have two of these soundcards, or rather an ST and an STX.  With the STX that I use in my office it is connected to Bowers and Wilkins MM1 Desktop speakers.  They have the USB connection option to the PC.  With this Soundcard I connect via a RCA to Stereo plug.  It is this USB connection that I had tried and is not as good as using the Asus Xonar soundcard.


hollowman's picture

Selecting 192k Sample Rate in Xonar's Audio Control Center gives best performance of std. 16/44.1 in my tests. Wish the Control Center allowed more direct DAC control, such as selectable digital filter (Slow/Sharp) and phase reversal. 

Agree that this Card is a decent value. Since Asus decison-makers (and Asus' direct competitors, like HTOmega) are probably reading these comments, here are three suggestions for future products:

1. Use dual DACs in diff mode

2 Use better DACs, such as ESS Sabre

3. Design/offer more advanced firmware filters (prefer. user selectable) and upsampling. This may be via decoder DSP or simply selecting amongst those innate in DAC chip. E.g., Min. Phase, Apodizing, etc. Also allow selectable upsampling.

That's all! #3 requires no costly PCB/topological redesign -- it's just software code re-writing. #1 and #2 can be done w/o too much PCB redesign. The Sabre chip maybe $20-30 more, but I'll be glad to pay that for the huge gain in performance.

Thx for your attn.!

Shalmaneser's picture

I'm looking for cable advice for my Essence STX II -> Yamaha CX A5000 connection. I don't have anything local for easy comparison. I don't go for marketing of oligonucleotides injected into titanium mono-filament cables jacketed with carbon nano-fibre woven kevlar bulletproof sleeves. (lets keep it somewhere under $6 a foot.)

Shalmaneser's picture

Does anyone have a guide to the various opamps that are usable in the STX II? I can't even find anything that characterizes the included/extra opamps that ship with the STX II. Thanks!