In the year of our Lord 2009, ASUS the giant was taking by surprise the entire audio world by launching Essence STX, a product that made history & which success to public has been over any expectations. It was the first soundcard of a general producer of electronic goods that targeted the audiophile segment & it did offer incredible facilities for that time: 124db SNR, top dac-chip from BurrBrown or amplified output for 6.3mm jack. Farther down the road, the things are familiar: it had a plethora of positive reviews, the high-rated Stereophile magazine had put it on a full front cover, and the sales skyrocketed any positive expectations. Essence STX will remain in the souls of many aficionados as the product that bind the pc users to the segment of hardcore audiophiles, the soundcard that had inspired a lot of people to rediscover music.


Design, features & ergonomy:

Essence STX was such a big hit, that it is still today the best internal soundcard, not even the ulterior launches made by Asus couldn’t change that. After almost 5years of ruling, it is time for an heir & hence we can introduce to you Essence STX II, a soundcard that represents the first major evolution of the original design.

Main features:

– STX II keeps the same excellent 124db signal-to-noise ratio, a respectable figure & worthy of an external quality DAC. It has kept same BurrBrown PCM1792 DAC-chip, a model also used in many top audio equipments (CD-player Primare I22, Atoll DAC 200 or player Fiio X5 being only a few of them).

– In order to reduce the jitter, ASUS had used premium oscillators TXCO (temperature compensated crystal oscillator).

–          Power supply has been improved by implementing LDO TPS 7A4700 si 7A3301 regulators from Texas Instruments. These in tandem with the German capacitors from WIMA can deliver a cleaner voltage & with smaller variations.

Essence STX II (1 of 1)

Xonar Essence STX II (1 of 1)

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–          Dedicated headphones amplifier TI 6120A2 – same as in the original version. The novelty here is represented by an extra gain level, intended for using IEMs with very low impedance & high efficiency.

–          A substantial change over the original version is represented by the presence of Muses op-amp from series 8920 & 8820. Even if they aren’t the flagship from New Japan Radio like in the case of Essence III, they are very high quality & of course, they’re expensive.

–          STX II has kept the same audio-grade capacitors from the Nichicon Fine Gold series unchanged from the original model.

–          DSP is also unchanged – Asus AV100 (rebranded C-Media CMI-8788 OxygenHD).

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Any experimented user will notice that we have in front of our eyes a fine product of craftsmanship. In addition to the features highlighted above one can notice the clean layout, with four distinct areas. Analogic circuits are separated from the digital ones because of the multilayer PCB with 2 shielding levels. For an extra protection, the analogic outputs have been covered with a metallic shield, this serving both as a protection & an esthetic purpose, being printed with the famous Qing tiger.

At the end of hardware analysis I want to remind you the already familiar “click” made be the soundcard when powering-up the PC, a sound specific to amplifiers’ repeaters. This is a good indication that shows us that on this soundcard won’t ever hear speaker clacks when turning on-off the PC. Once we deactivate line-in/

mic-in, they will be truly deactivated & in no way they will influence / amplify by any means the background noise.

Essence STX II layout

Essence STX II LDO

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The driver:

In the moment I had installed the soundcard there weren’t any drivers on ASUS’s website, so I had to use the CD received in the package. The driver worked flawlessly, I didn’t encounter any installation or utilization problems. Essence STX II supports ASIO, as well as Kernel Streaming or Wasapi. I am old-school & so I use KS given the chance.

The software bundled with Essence STX II is very resembling to that of the original soundcard, being user-friendly & well defined. For better a stereo sound I recommend that you DO NOT activate the plethora of processing & equalizers inside the soft. The best results I got when I had Hi-fi mode activated & default sampling rate of 44.1KHz.

Essence STX II has the most advanced visualization algorithm multichannel – Dolby Headphones. I highly recommend you to use it with confidence in games and movies, it brings a plus of charm & a more real sensation of immersion into action.

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I’ve noticed with pleasure the detailed & very liquid sound which STX II can deliver. If I hadn’t known beforehand what am I listening to, I would’ve bet that I’m linked to an external consecrated solution. The sound flows smooth, relaxed & it tickles the eardrums in a very nice way. I’ve listened to the whole album Call Me Irresponsible from Michael Bubble with a pleasure I haven’t ever felt on my day to day soundcard, Xonar Xense. Artist’s voice is smoother, better defined, natural. The piano or the trumpets sound much closer to those from a live concert, and the timing is superior.

Michael Bubble’s album had to be followed by an album from Pink Martini, so I had a glass of Mateus’s frizzante rosé & I continued the audition. Sympatique proved to be an album which emphasizes the ability of the soundcard to create a large soundstage and a good separation of instruments. The scene doesn’t have the depth which one can encounter on high-end sources, but it is wide & well distributed in the face of the listener. Probably the lack of profoundness had let me the impression that compared to M2Tech Young I’m closer to the scene. This detail isn’t necessary a bad thing, it can be a plus, depending on the preferences of the listener.

I had wanted to test the limits of the soundcard, hence I’ve called a heavy category album: Stravinsky: The Song of the Nightingale, The Firebird Suite, The Rite of Spring. I’ve listened many times the album played under the magic wand of Eiji Oue & I’d quickly felt that Essence STX II limits the pleasure of the audition. The attacks, the rhythm interruptions & very crowded passages, with high dynamic, sound mixed together in many moments, lacking that lucidity which captures your attention on such an audition. It is a normal thing, I’ve tested convertors with much higher expectations & they can’t finish this album in a good note. STX II plays decent, but it doesn’t shine.

After this elitist incursion I’ve descended down to earth & I’ve listened to some plays from The Carnival –Wyclef Jean & Amelie – Yann Tiersen. Very good bass & the rhythm from Guantanamera, superb violin in J’y Suis Jamais Allé. I noticed again the remarkable resolution surprising for the class which it belongs to & also its ability to reproduce the difficult instruments to a credible level.

I’ve compared STX II with the original STX, with Xonar Xense & with Xonar D2/PM. The new model wins quite clear against Xense & D2/PM & it has an important edge against its elder sister. The sound is more detailed, more liquid, more pleasant to listen to on the longer term. The soundstage is more generous on the STX II, the latest declination of the Essence range offering a better sound experience than the previous models.

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Headphones amplifier:

Essence STX II’s ability to amplify headphones is similar to that seen on Xense & STX models. TI 6120A2 chip leads very well medium models like HD558, AD700x or K550, but it can’t handle heavyweights like HD800 or Q701. The latter ones are ok to listen to, but I strongly recommend a dedicated headphones amplifier.


I’ve also tested the multichannel extension with the help of an older Onkyo receiver which I had in house by chance. It’s a 1007 model since when Onkyo made good quality hardware. STX extension sounds extremely similar to my old Xonar D2/PM board, so in case you own such a model & you use it with a home-cinema system, you don’t have any reason to change it. The way it performs as a source for multichannel sound is competent, comparable to that of a medium priced receiver.

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Asus Xonar Essence STX II is not a completely new model, but it represents a clear & consistent evolution of the most successful soundcard targeted to PC. It represents, at this time, the best & most complete internal solution & I highly recommend it to those who want a top soundcard. I foresee for STX II a lightning sales success & I consider that ASUS has seriously consolidated its position as a leader for this segment.


– very good construction

– detailed, liquid sound

-big & well rarified soundstage

-top features

– high tuning possibilities.


headphones amplifier could’ve been better

– just an evolution, I’d preferred a revolution. 🙂

Essence STX II pack

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  1. For better dynamic – for Stravinsky – you have to swap OP-AMPs – put the 8820 in I/V and 8920 in buffer. J-FET have a high slew rate and are not very dynamic if used in I/V stage.
    Tested with MUSES01D and MUSES02D.


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