Asus Xonar Essence STX Review

hardnrg - 2009-04-02 01:29:10 in Sound Cards
Category: Sound Cards
Reviewed by: hardnrg   
Reviewed on: May 14, 2009
Price: $185


Asus really doesn't need any introduction, but in case you didn't know, the company makes pretty much everything computer-related, from complete desktops, laptops and server systems, to individual parts such as graphics cards, soundcards, and cases. Once again, I am writing this review on my Asus EeePC 1000H laptop (netbook), one of the more recent additions to Asus' product line that garnered more public attention to the company. High performance computer enthusiasts have known Asus for its motherboards for many years now, and the specialized designs have put Asus up amongst the top two or three companies to consider for the best overclocking motherboards for current and cutting-edge processor platforms.

As manufacturers add more and more features to their motherboards, such as HDMI, optical and coaxial digital audio, 8 channel analog audio, it does prompt questions over what are the reasons for getting a separate soundcard since you can get most or all of the connectivity and features with onboard audio, and therefore might not necessarily require a soundcard to hook up to your sound system. High-end soundcards address the needs of audiophiles with ultra-clean and precise sound, devoid of noise and interference, and with endless reserves of dynamic sound throughout the audio spectrum for powerful and yet detailed sound. The Xonar Essence STX promises all this and more! This soundcard has a headphone amplifier on the card that claims to have the ability to drive any pair of headphones. Standard soundcards can drive regular or entry-level headphones and headsets, but when you hook up some higher-end full-size headphones, the lack of signal power means that the resulting sound is lifeless or distorted. The Essence STX should be able to supply extremely high end audio to either headphones or amplified speaker systems, so this is what I will be investigating throughout the review.


Closer Look:

This design is reminiscent of ancient Chinese artwork and legends, and grabs your attention immediately when you look at the front of the box, evoking questions and curiosity. Questions like "what the hell is a tiger doing on the soundcard box?" and "what does this have to do with the sound?" Asus has decided to use a "Chime of Tiger" design for this soundcard, to represent its advances in audio technology. Fair enough, an endless pursuit of sonic perfection since the dawn of time then? Well, 4000 years apparently. Either way, I like it. I like the sound of that. Will I like the sound of the soundcard though?











One side of the box lists the contents of the retail box and the system requirements in order to use it. The other side gives some key details on the soundcard specifications, the connector types, and the feature set of the soundcard drivers.



You might be thinking, "is that it?" Well, no, it isn't. The front of the box lifts up to reveal the soundcard itself, with a labeled picture of the card above, explaining the benefits of the major components on the card. The available connectors are also listed clearly with explanations, and finally a few major reasons for why this soundcard is unique and superior to the plethora of other soundcards out there.



Inside the box, unlisted in the contents, are two posters. These were an unexpected surprise, and it's a bit of a shame they are folded as they could look quite nice up on the wall. Maybe Asus could include some high-resolution images on the driver CD to print out on a photo printer. I dunno, I just hate creases in posters. Anyway, to the more important contents of the box, you get an Audio Precision Test Report, a Quick Start Guide, a driver/application/manual CD, a 2x RCA/phono (male) to 3.5mm stereo (female) adaptor lead, a 1/4" stereo jack plug to 3.5mm stereo jack socket adapter, and an optical jack adapter to give you a TOSLINK digital optical output.



The Audio Precision Test Report deserves some explanation. It is a detailed technical report including data and graphs produced during the analysis carried out by Asus on state of the art testing equipment. Without relative comparitive data, it could be difficult to decipher what some of the graphs really mean, so if you haven't looked at audio signal performance graphs before, the whole report can be summed up as "excellent."



I like high performance and technical precision, but also like creative design and presentation, so I appreciate the textured heavyweight paper Asus chose to use for the report cover. It's embossed with the Chime of Tiger design, "gilded" lettering, and a golden elasticated cord to bind the report. Simple, minimalistic design: something I love.


Closer Look:

As you probably already noticed, the card itself sports the Chime of Tiger design on an EMI (electro-magnetic interference) shield. This metal shield acts as a Faraday cage, to block any EMI from other components inside the computer. It's not a new idea, and previous cards in the line of soundcards from Asus, such as the D2, have a similar EMI shield. Creative has put EMI shields on some of the more recent Soundblaster soundcards, but the Asus EMI shields are more substantial and I find the brushed metal finish more aesthetically pleasing. Unlike the Xonar DX and D2X soundcards, the Essence STX does not have a PCI counterpart, and is only avaiable in PCI-E x1 form. The reverse side of the card is unsurprisingly plain, although each of the headers and sockets are labeled on the PCB.


















On the back of the card, from top to bottom, you have right and left line-level RCA/phono outputs. These are intended to be connected to stereo computer speakers or a stereo amplifier. If you have computer speakers with a 3.5mm stereo jack plug, you can use the included adapter lead to convert these two RCA/phono sockets to a 3.5mm stereo jack socket. Next, there's a 1/4" stereo jack socket for driving headphones directly from the onboard amplifier. Similarly, if your headphones have a 3.5mm stereo jack plug, you can use the 1/4" to 3.5mm jack adapter to enable connectivity. The second 1/4" socket can be used either as a microphone or as a line-level stereo input. The last connector is a combination RCA/phono (coaxial) and optical digital output. This lets you have multi-channel (e.g. 5.1 surround) audio via a digital interconnect cable. Again, you can use the included optical adapter if required. I like the range of inputs and outputs on the back of the card, the use of more substantial connectors than 3.5mm stereo jack sockets, and the fact that the digital output is separate to the microphone and line input, unlike the combination jack of the Xonar D1, and those of the X-Fi series.


Along the top of the EMI shield there is a cutout for the Auxiliary and Front Panel connectors. After using Soundblaster cards without a standard front panel audio header for many years, it's somewhat of a novel idea to have high quality audio on the front panel of a computer case. The Asus logos on the EMI shield are in raised lettering; I like how Asus chose to place the logo along the top edge of the EMI shield, as you can see it when the soundcard is installed, especially if you have a panel window on your computer case.


The last two connectors on the card are a 4-pin "Molex" power connector and a S/PDIF header. The "Molex" input supplies power to the amplification sections of the card rather than relying on the 12V and 3.3V pins of the PCI-E slot. The S/PDIF header allows you to connect the soundcard to a graphics card with an HDMI output. The J14 header is undocumented.


The AV100 is the same C-Media OxygenHD (CMI8788) sound processor used on the rest of the Xonar line and on HDA/Bluegears/Auzentech cards. It provides a mixture of hardware and software support for DirectSound/DirectSound3D, OpenAL, and A3D.


To the left of the AV100, you can see the Cirrus Logic CS5381 ADC used for the analog inputs. The DJ100 is apparently an AC'97 codec DAC (C-Media CMI9780), and therefore the microphone section of the AC'97 feature set is used as a pre-amp for the microphone (and front panel microphone). AC'97 is not synonymous with the highest quality, but as this soundcard is tailored toward high-end audio playback, it's not really an issue. You could always get a proper microphone pre-amp if you wanted to do some production-level recording from a microphone. The microphone input cannot be configured as balanced anyway.


The New Japan Radio NJM5532 and Texas Instruments R4850 op-amps are used for the line-in/microphone input. Asus chose to use miniature relays to do the switching between line-in and microphone modes. My theory is that the relays route the signal through the NJM5532s for the line-in, or the R4850s for the mic mode. The use of relays to switch the routing eliminates the signal loss that you would get if you used solid-state switching.


I had to take the EMI shield off to see what was hiding underneath. You can see it's fairly thick metal and not like some "Coke can" thickness shields.


Underneath, you can see the analog output stages, and the internal analog input stages. These areas are shielded from each other with a small shield "wall."


Sanyo OS-CON capacitors are used as smoothing capacitors, to ensure clean power delivery from the "Molex" connector. Another Sanyo OS-CON is used for the S/PDIF output. The remaining electrolytic capacitors on the PCB are Nichicon FG "Fine Gold," and are specifically designed and manufactured for high-end audio equipment. It's very impressive to see high-end capacitors used throughout.


The Burr-Brown PCM1792 DAC is used to feed the analog output stages. This DAC is very high end, and is reason enough for audiophiles to use this soundcard simply because most other soundcards use inferior DACs and therefore the analog outputs on other soundcards don't perform as well.


Probably the most important and unique feature of the Essence STX is the Texas Instruments 6120A2 headphone amplifier chip. This is a very capable dedicated amplifier chip for headphones, and can handle impedance up to 600 ohms! This chip is the basis of some standalone high-end headphone amplifiers.


Two New Japan Radio NJM2114 op-amps are used for the left and right channels, these either pass the signal to the 6120A2 headphone amplifier, or to the RCA/phono line-level output via the National Semiconductor LM4562 op-amp. Again, the switching between outputs is implemented with the NEC relays to minimize signal loss. If you want to change the sound of the headphone output, you would replace the NJM2114 op-amps. Changing the line-out sound is achieved by replacing the NJM2114 and/or LM4562 op-amps.



The op-amps are all DIP8 packages, and can be pulled out and installed without any tools. You might need to use a tool if you have large fingers and thumbs, but it is still a very simple, quick and painless process.


It's nice to see metal film capacitors used for the LM4562 op-amp. These are a step above electolytics for most audio applications, but their physical size versus capacitance prohibits usage all over the soundcard.


Closer Look:

The Quick Start Guide is, as you would expect, fairly basic and only really of much use to someone who hasn't installed computer hardware before. The guide tells you what the connectors are, how to install the card, and instructs you to install the driver package on the included CD. When you insert the disc and launch the setup program, you will see this window:



















Clicking on "Read me" brings up some release notes about the driver version.


Clicking "Browse CD" reveals the Quick Start Guide on the CD, kind of handy if you tend to lose manuals.


The User Manual is on the CD as well and explains the connectivity options in greater detail, with examples of external speaker systems, headphones, headsets, microphones, and other external devices. It also gives a good explanation of the Xonar Audio Center, which is the software user interface of the soundcard.


To install the driver, you click on the "Audio Driver" text, and a dialog box pops up to remind you to make sure that the "Molex" power connector has been connected to the PSU.


After accepting the license agreement, it zips through the installation and then prompts you to restart the computer.


When you restart the computer, you can find the Xonar Audio Center in the Start Menu (Programs\ASUS Xonar Essence STX Audio\Xonar Essence STX Audio Center), and as a small blue and black icon in the task tray. When you open it first, you can see a 10-band spectrum analyser and indicators for modes and volume level in a graphical display. To the right of this display, there is a large volume knob, a Smart Volume Normalization (SVN) button, a Mute button, and buttons for different mode configurations (Music, Movie, Hi-Fi, Games, and GX). GX is the support for EAX games.


Clicking the small triangle/arrow button underneath the graphical display reveals more controls. The first page, Main, determines the output device, and any DSP or encoding applied to the output. The Audio Channel setting only applies to Vista, and is intended to match the sound source. So, two channels for music, six channels for DVD, and eight channels for 3D games. It's a bit tedious to have to switch this, but really, I only switch this a few times a day, if at all.


Similarly, the Sample Rate is meant to match the sound source for the best quality (avoids resampling). So 44.1 KHz for music, 48 KHz for DVD, 96 or 192 KHz for DVD-Audio, BluRay, etc.


Here is where it starts to get interesting. The Analog Out switches between the Headphone output, line-output (two speakers), or front panel (FP headphone, FP speakers). When you choose an output, the other outputs are muted, so you can't simultaneously drive all the outputs, except for the S/PDIF Out in PCM mode.


If you switch the S/PDIF Out mode to Dolby Digital Live, the analog outputs are all muted. In 2-channel source mode, there is a blue icon to the right of where it says Dolby Digital Live, clicking this reveals an option which defaults to automatic upmixing to 5.1 surround. Somewhat strangely, with four channel sources, there is no upmixing to 5.1 option. I really don't know of many quadrophonic sound sources, especially in digital format, so it's a bit of a non-issue.


Here is an example of the intended configuration of the soundcard for listening to DVD or other 5.1 media. You set the source to six channels and then either have the output set to two Speakers with Dolby Virtual Speaker, or set to Headphone with Dolby Headphone. Both configurations work very well, and I prefered using this to plain stereo without Dolby virtual surround for multi-channel sources.


The same configurations can be applied for stereo speakers or headphones when listening to 8-channel sources such as games and some of the more advanced variants of movie surround sound.


In Headphone mode, there is a hammer icon to the right, and when clicked, reveals a setting to select the gain of the amplifier! This amazed me, as it lets you match the amplification to drive any headphones. During my tests, I thought the soundcard was somewhat lacking for driving my AKG K 701 headphones until I increased the gain level to High Gain instead of the default Normal Gain. This gain setting also applies when the output is set to Front Panel Headphone!


When you change the gain setting, you are warned about the possibility of over-driving the headphones. Overclock your headphones! Seriously though, if you increase the gain and have the volume on max when some low impedance headphones are connected, you could destroy them quite easily. I have some Westone UM2 in-ear monitors that cost $300, this is just one example of low impedance headphones that could easily be damaged if you select the gain level incorrectly.


In XP, you would have separate level controls for Wave, MIDI, etc. In Vista, you only get Left and Right level sliders. These default to 75%, which is equivalent to a zero gain/cut (±0 dB), so you should leave these as they are and adjust the volume with the master volume control. The recording levels default to 100%, which is also ±0 dB. As well as being selected for recording, the microphone, line-in, and auxiliary inputs can be monitored through the output device (speakers/headphones) by pressing the hexagonal/eye button below the respective source. The microphone has advanced settings by clicking on the spanner button. You get the usual microphone boost option, and also an option for whether or not the microphone is the front panel. This is an either/or deal with relay switching.


The Effect section has EAX-like reverb presets for Environment effects. These basically make music sound crap like you're in a cave or something. The EQ section on most soundcards is somewhat lacking, but not here! The presets range from OK to comical, but give you an idea of how much the EQ works, and the great thing here is the EQ works very well! I ended up with about seven or eight presets for each set of headphones, gradually tweaking toward a very impressive sound. Normally raising the bass frequencies doesn't reach a satisfying level or distorts. I'm not a bass-head, but I like a little fuller bottom-end, and the Essence STX is capable of supplying massive amounts of clean, precise bass. The ±20 dB gain/cut range lets you sculpt the sound to suit any set of headphones. The Karaoke section is basically stupid. It's only there because the driver/mixer is common across all Xonar soundcards. If you are a budding Pop Idol, then yeah, it might be good. The Vocal Cancellation is essentially not going to ever happen properly, you should look for instrumental tracks if you are serious about karaoke or recording vocal tracks.


The FlexBass is a bass redirection feature. It works well for multiple speaker setups where you have a subwoofer and satellite or bookshelf speakers, but for the Essence STX you could only use it as a bass cut filter for headphones or stereo speakers by setting the speaker type to "Small" and then enabling FlexBass. The VocalFX section is another gimmicky set of features. You can apply the Environmental reverb or pitch-shifting Karaoke effects to your voice for Skype, MSN, games, etc. It could be funny for a prank call or having a comedy voice in online games, but that's about all the fun I would have.


The Essence STX has ASIO 2.0 support, which means it can bypass the Windows mixer. Foobar2000 is a free audio media player that supports various plugins, so I loaded it up with ASIO and WASAPI support. WASAPI is another method of bypassing the Windows mixer. By default, foobar2000 would output to the default sound device via DirectSound.


With the ASIO plugin loaded, you can go to the Output->ASIO Virtual Devices and click on Add New. On the ASIO Virtual Device Editor you can click on Configure and then set the latency lower. This doesn't make any difference in audio quality, but it makes the response slightly faster, so you may as well.


Then, the Xonar Essence STX is available as an ASIO device.


You could also choose WASAPI or DirectSound output modes.




Audio Performance Output Signal-to-Noise Ratio (A-Weighted):
124dB for Front-out,117dB for Headphone-out (600ohms) dB
Input Signal-to-Noise Ratio (A-Weighted):
118 dB
Output THD+N at 1kHz:
0.0003% (-110dB) for Front-out, 0.001% (-100dB) for Headphone-out
Input THD+N at 1kHz:
0.0002% (-113dB) for Line-in
Frequency Response (-3dB, 24-bit/192kHz input):
<10Hz to 90KHz
Output/Input Full-Scale Voltage
2 Vrms (5.65 Vp-p)
Bus Compatibility PCI Express:
116dB for front-out, 112dB for other channels dB
-PCI Express Rev. specification compatible
-Compatible with X1, X4, X8, X16 PCI Express slots
Main Chipset Audio Processor:
ASUS AV100 High-Definition Sound Processor (Max. 192KHz/24bit)
24-bit D-A Converter of Digital Sources:
Texas Instruments PCM1792A*1 for Front-Out (127dB SNR, Max. 192kHz/24bit)
24-bit A-D Converter for Analog Inputs:
Cirrus-Logic CS5381* 1 (120dB SNR, Max. 192kHz/24bit)
High Fidelity Headphone Amplifier:
Texas Instruments 6120A2*1 (120dB SNR, 100dB THD+N @ Vcc±12V, RL=600Ω, f=1kHz)
Sample Rate and Resolution Analog Playback Sample Rate and Resolution:
4.1K/48K/96K/192KHz @ 16/24bit
Analog Recording Sample Rate and Resolution:
44.1K/48K/96K/192KHz @ 16/24bit
S/PDIF Digital Output:
44.1K/48K/96K/192KHz @ 16/24bit, Dolby Digital
S/PDIF Digital Input:
44.1K/48K/96K/192KHz @ 16/24bit
ASIO 2.0 Driver Support:
Supports 44.1K/48K/96K/192KHz @16/24bit with very low latency
I/O Ports Analog Output Jack:
RCA jack *2 (Front R / Front L), 6.30mm jack*1 (Headphone out)
Analog Input Jack:
6.30mm jack *1 (Shared by Line-In/Mic-In)
Other line-level analog input (for CD-IN/TV Tuner):
Aux-In (4-pin header on the card)
Digital S/PDIF Output:
High-bandwidth Coaxial/TOS-Link combo port supports 192KHz/24bit
Front-Panel Header:
Shared by Headphone out / 2 channels out / Microphone in
S/PDIF Header:
Connects to compatible graphic cards for HDMI output




Driver Features Operation System:
Windows Vista/XP(32/64bit)/MCE2005
Dolby® Technologies:
Dolby® Digital Live
Dolby Digital Live encodes any audio signal on PC in real-time to Dolby Digital (AC3) 5.1 surround sounds to your home theater environment through one single S/PDIF connection

Dolby® Headphone
Dolby Headphone technology allows users to listen to music, watch movies, or play games with the dramatic 5.1-channel surround or realistic 3D spacious effects through any set of stereo headphones.

Dolby® Virtual Speaker
Dolby Virtual Speaker technology simulates a highly realistic 5.1-speaker surround sound listening environment from as few as two speakers.

Dolby® Pro-Logic IIx
Dolby Pro-Logic II is the well-known technology to process any native stereo or 5.1-channel audio into a 6.1- or 7.1- channel output, creating a seamless, natural surround soundfield.
Smart Volume Normalizer™:
Smart Volume Normalizer™
Normalizes the volume of all audio sources into a constant level and also enhances your 3D sound listening range and advantages in gaming
Xear 3D™ Virtual Speaker Shifter:
Virtual 7.1 speaker positioning
Magic Voice™:
Xonar Essence STX provides VocalFX, the latest vocal effect technologies for gaming and VoIP, including:
-VoiceEX: produces vivid environmental reverberation for your voice in EAX games
-ChatEX: emulates different background environment effects when you chat online
-Magic Voice: changes your voice pitch to different types (Monster/Cartoon) for disguising your real voice or just for fun in online chatting
Karaoke Functions:
Music Key-Shifting and Microphone Echo effects like professional Karaoke machine
Professional Bass Management/Enhancement system
3D Sound Engines/APIs:
Vista: DirectSound3D® GX 2.5, DirectSound® HW, DirectSound SW, A3D®1.0, OpenAL generic modes, 128 3D sounds processing capability

XP: DirectSound2.5 SW, A3D®1.0, OpenAL generic modes, 128 3D sounds processing capability

DS3D GX2.0:
DS3D GX 2.5 gaming sound effects and DirectSound 3D hardware enhanced functions on Windows Vista. (DirectX/DirectSound 3D compatible)
Bundled Software Utility  
Accessories 1 x 3.5mm-to-RCA adaptor cable
1 x S/PDIF optical adaptor




I disconnected all the fans, even the CPU heatsink fan, and was left with just the PSU fan. The PSU fan emits a soft sound, it is pretty much inaudible in terms of fan noise. The noise from the hard disks both from idle and seeking vibrations was too annoying to ignore, so I took them all out and laid them on small rectangles of sound-isolating foam/sponge. The door to the room was closed during testing, and with no other equipment running, you could literally hear a pin drop.

The two most intriguing features of the Xonar Essence STX to me are the onboard headphone amplifier and the purity of the line-out. I wondered how the soundcard's amplifier would compare to my own custom made Class A headphone amplifier. I am also interested in seeing how it measures up to the line-level output of my modified XtremeMusic soundcard. Following cotdt's guide at, I have upgraded the front stereo line-out's op-amp and the power capacitor, as well as bypassing the decoupling output stage, to raise the sound quality to about the highest possible.


Testing Setup:

Comparison Sound Cards:



Listening Gear:







Subjective Listening:



Test Results:

Rightmark Audio Analyser (RMAA) works by sending test signals out of the soundcard and then recording the signals back into the soundcard, and making comparisons and measurements to assess the soundcard performance.

I chose to use a loop-back cable for RMAA because if you use internal hardware loop-backs, some soundcards bypass some of the output and input stages, to pipe the playback audio directly into recording. This is essentially cheating, and doesn't represent an actual loop-back, so an external cable ensures each soundcard is doing a complete loop-back during the tests.

The test results page shows you the average values across the frequency range. The frequency response you want to be as near to flat as possible, so small numbers are better. The noise level is the amount of background hiss, etc, so this needs to be as low (large negative values) as possible. The dynamic range is almost always nearly the same as the noise level, except positive. The remaining measurements of distortion, noise, and crosstalk, need to be as small (or large negative values) as possible. The Xonar Essence STX uses an audiophile level DAC and op-amps on analog outputs and a high quality ADC and op-amps on the inputs. You can see the advantages gained by using superior components, I'd say the capacitors and DAC are the reason for the higher performance over the modded X-Fi XtremeMusic.

There are two sets of results here. The first set was conducted on all soundcards, at 24-bit and 48 kHz. The second set was run at 24-bit and 96 kHz, but only on the modded X-Fi XtremeMusic and the Xonar Essence STX. The X-Fi can only record at a maximum sample rate of 96 kHz, so this was the highest test I conducted.












24 bit, 48 kHz


Each of the graphs are included here to show the measurements vs. frequency.





24-bit, 96 kHz


Each of the graphs are included here to show the measurements vs. frequency.






The noise level is very low for all soundcards, but the lead is taken by the Xonar cards, the Essence STX beating the rest of the pack. This trend continues until we get to Stereo Crosstalk, where the modded X-Fi XtremeMusic has better stereo separation from about 2 kHz upwards. In the 24-bit, 96 kHz tests, the modded X-Fi XtremeMusic has a strange rolloff at the audible frequency extremes, whereas the Xonar Essence STX has a much truer, flatter response. Again, the Stereo Crosstalk is the only test where the modded X-Fi beats the Essence STX, and it's only at frequencies above ~2 kHz.



The "Hi-Fi" button on the main section of the Xonar Audic Center disables all DSPs and EQ, setting up the soundcard for pure, unaltered sound. I used this for the tests using the line output of the Essence STX, when connected to my M³ headphone amplifier. For the tests carried out using the soundcard's headphone output, I enabled a custom EQ curve to apply an approximate loudness curve, making the sound as perfect as possible, to my ears, on each set of headphones.

I ended up listening to music for two weeks, so the tracks listed below are just a few of the many I listened to while setting up the EQ for each headphone, and enjoying countless hours of high-quality sound and music. The first two are from electronic genres, the first a heavy, slamming dancefloor-oriented track, and the second a much more laid-back musical piece. The next track is a Celtic style song with Eastern influenced instrumental arrangements. The final track is a classical piece, there are no vocals and no electronic gear, just traditional instruments.

All the tracks were ripped from CD using ExactAudioCopy, encoded to the lossless FLAC audio codec. This means the exact bit-for-bit signal of the CD track is maintained and reproduced upon playback. The advantage in regard to this test is that there is no noise from the optical disc drive whilst listening to the music. Foobar2000 was used as the media player as it supports ASIO playback.

Since the Xonar Essence STX is in a different league to the Xonar D1 and onboard sound, I decided to limit my testing to comparing it to my modded X-Fi XtremeMusic.

















Test tracks:


X-Fi line-out to M³ headphone amplifier

This is my current high-end listening setup. I built the headphone amplifier myself and tailored the bass boost section for the AKG K 701 headphones, and my preference in tonal balance. The kick drum beats in "Aqualight" are powerful, deep and clean on the K 701, but a touch too emphatic with the HD25 (due to the tailored bass curve of my M³ amp). The synth pads and glockenspiel hits in "Das Glockenspiel" echo and fill my aural periphery with lush and dream-like wonder on the K 701, the HD25 feels a little bit more enclosed yet still just as detailed. The vocals of Loreena and the choir in "The Mystic's Dream" are quite breath-taking. I like the flute, piano and string sounds in "Aquarium," and from the X-Fi I again feel like I'm in an enhanced state of mind.


Essence STX line-out to M³ headphone amplifier

Swapping to the Xonar's line out, it quickly became quite apparent that distinguishing the difference between my modded X-Fi XtremeMusic and the Essence STX would be difficult at best. This is probably due to the fact that I replaced the op-amp on the X-Fi with an LM4562, the very same as the one on the Xonar. The differences are down to the capacitors and DAC on each card. I would say that overall, the Essence STX has a slightly purer sound, the XtremeMusic seems as though it has a touch of tube-like distortion in comparison. Interestingly, the X-Fi appeared to have a slightly wider stereo image than the Xonar, and this correlates with the Stereo Crosstalk tests conducted with RMAA after the listening tests.


Essence STX headphone output

With the K 701, at first I thought the onboard headphone amplifier of the soundcard was somewhat lacking, kick drums didn't seem to hit as hard, consonants in vocals weren't as pronounced as when using the M³ amp. However, despite the low impedance (62 Ω) of the K 701, they are notoriously harder to drive than you would suppose. Increasing the gain to High Gain (+12 dB for 64 to 300 Ω) in the HP Advance Setting provided much more dynamism, so much so that I was actually taken aback by the difference. There was much more bass slam in "Aqualight" and all the heavier electronic music I listened to, and there seemed to be an almost endless reserve of bass when using the HD-25 in particular.


I think critical listening of music is the most telling test of a soundcard's sound quality, and the Xonar Essence STX's performance was stellar. Whether listening to music through speakers, an external headphone amp, or using the onboard headphone amplifier, music lovers and audiophiles will definitely enjoy the experience. As I mentioned, the music test was extensive, and I would say that I still prefer my M³ headphone amp and AKG K 701 headphones, but the margin is fairly small. I have to point out that I customised my amp to the sound of the K 701 headphones. This is apparent when using the Sennheiser HD25-1 II headphones. The bass curve I implemented in the M³ amp accentuates the mid to high bass frequencies a bit too much, so even though it is a variable bass gain, it just doesn't work as well as using the Essence STX EQ controls.


Vista has a slightly different driver model to Windows XP, so it's important to test a range of games to cover the different game audio engines, and the soundcard hardware support available. The GX mode of the Xonar Essence STX is similar to ALchemy in that it provides EAX enhancement for games played in Vista.





















Test Games:


Game Mode: Enables Dolby Headphone (DH-2: Livelier Room) or Dolby Virtual Speaker (Reference Mode)

At my main workstation desk, I have bookshelf speakers on stands to either side of the primary monitor. When in 2 Speaker output mode, enabling Game Mode activates the Reference Mode preset of the Dolby Virtual Speaker. This is a virtualization effect that makes the sound appear to be coming from beyond, behind, and further to each side of each speaker. For a game outputting multi-channel audio, I prefer this surround enhancement over pure stereo, as it gives you a greater aural spacial awareness.

Switching over to Headphone output, the Game Mode enables the DH-2 surround virtualisation preset. As with the Xonar D1, this sounds the best as the DH-1 preset is too subtle, and the DH-3 preset over-processes the sound and begins to sound metallic. It's quite a different experience when playing games with headphones as opposed to speakers, and often I had to lift the earcups off my head to check the sound wasn't coming from the speakers, even though I knew that the line out is muted when in headphone mode!

Game Mode + GX: This enables the EAX support

All of the games worked very well with the GX mode enabled. Crysis and Call of Duty 4 do not use EAX, but I tested them anyway to make sure the GX feature didn't negatively affect the sound. I couldn't discern any difference, and would say the sound of non-EAX games is completely unaffected, as it should be.

Unreal Tournament 3 and Call of Juarez use EAX. Overall it works very well, and I actually tried all my games for EAX compatibility. The support is there for EAX versions 2 and 5. Why versions 3 and 4 aren't supported is a bit of a mystery, it's really down to the C-Media implementation, but most games are version 2 or 5 anyway. I only had one game that had EAX 4, and the option was grayed out and not selectable in the game options. The GX mode isn't flawless and not an exact copy of EAX, some of the reverb sounds appear to be programmed as a multi-tap delay that sounds a tiny bit odd for one or two areas on some levels in UT3. There is some room for improvement, but you would only notice the difference if you have literally played hundreds of hours of Unreal Tournament!




After the addictive gaming session, I was eager to find out what pre-recorded multi-channel audio sounded like!

I watched The Matrix trilogy, and the THX Demo Disc II.
















As with the gaming tests, the Dolby Virtual Speaker mode is good, but the virtualisation effect of Dolby Headphone is much more impressive. It is as if the movies have been re-recorded as a binaural audio track, specifically for headphones, to make the sounds appear to come from around the room rather than directly from the earcups on either side of your head. It makes sense that if anyone is going to nail headphone surround virtualization, it would be Dolby Laboratories. You really have to hear it to appreciate how well Dolby Headphone works, but suffice it to say, the surround sound simulation works better than Creative's CMSS and the headphone virtualisation modes found in ffdshow and Cyberlink PowerDVD. It is literally the best surround sound effect through headphones that I have ever experienced, and I prefer watching movies this way when at my desk, or when watching loud action movies late at night when playing sounds through speakers would be unfair on the neighbors!



As with most products, I was slightly apprehensive about the Xonar Essence STX before I heard it. I asked myself, how could a small, simple amplifier on a soundcard perform anywhere near as well as a standalone headphone amplifier? The answer is, it performs spectacularly thanks to the high quality components producing the line-level audio signal, as well as the very capable headphone amplification circuitry.

Probably what surprised me the most was how well the multi-band EQ works to tailor the sound to any headphones. I feel this is because following the EQ section with powerful amplification delivers rich and detailed sound that just isn't possible on an unamplified soundcard. If you have high-end headphones without a standalone headphone amplifier, the onboard headphone amp of the Essence STX will serve you well, and you may find that you don't even need a separate amplifier. Though I still find it hard to believe, it really is that good.

The Dolby Headphone mode is found on the rest of the Xonar line of soundcards, but because the Essence STX has the amplified headphone output, it is even better, and performs well for pre-recorded multi-channel audio in movies as well as live multi-channel audio in games. Coupled with the GX mode's support for EAX environmental effects, this gives you what I would consider the best soundcard for games. I believe that games should be played using headphones, for greater immersion, spacial awareness, and for the optimal set-up for gaming when using voice-chat features either in-game or using applications such as Ventrilo or TeamSpeak.

It's not all about headphones though, and the high quality sound is also available through the analog stereo line level output (RCA/phono) so that you can use the soundcard with speakers or even an external headphone amplifier. If you want to use the Essence STX with a multi-speaker surround sound system, you can enjoy 5.1 surround sound from games and movies as long as your computer speakers or AV receiver has a digital input. This can either be optical or coaxial, and the Dolby Digital Live feature means you can have proper surround from games, and with the upmixing feature, you can even play music through all of the speakers.

I really wasn't sure if there would be a soundcard to beat my modded X-Fi XtremeMusic, but the Xonar Essence STX beats it both in sound quality, features, and compatibility. The Creative drivers, both for the Audigy and X-Fi Soundblaster cards, can cause severe problems in Vista, causing the whole operating system to lock up, clicks and digital noise in the audio signal, and some features such as microphone input to not work at all! The Essence STX doesn't have any of these problems, and functions properly without issues while sounding better than any Creative soundcard.

If you don't really use headphones and prefer speakers, or only have a cheap headset for Skype calls or something, it would make more sense to go for the Xonar D2 or one of the newer Xonar soundcards with more features and connectivity for home cinema equipment. However, if you have high end headphones, enjoy online gaming, or watch movies at night, I cannot recommend the Essence STX highly enough. It is now my favorite soundcard and has taken the crown from my modified X-Fi XtremeMusic, so if you love sound and love headphones, do yourself a favor and get the Xonar Essence STX.