Xonar Essence STX II Sound Card (90YA00MN-M0UA00)

  • Essence STX II and STX II 7.1 build on the success and huge popularity of ASUS Essence STX
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Stock Code: SC-021-AS

EAN: 0886227682638

MPN: 90YA00MN-M0UA00

Manufacturer: Asus

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Product information:

Xonar Essence STX II Sound Card (90YA00MN-M0UA00)

Hi-Fi quality sound card with 124dB SNR clarity, top-notch headphone amplifier and premium TCXO clock source.

  • Industry-leading 124dB SNR (signal-to-noise ratio) audio quality inherited from the revolutionary and widely-acclaimed Xonar Essence ST/STX
  • Ultra-low jitter with premium TCXO clock source
  • Clean and consistent power supply thanks to high-fidelity low-dropout (LDO) regulators and WIMA® capacitors for uncompromising sound
  • Top-notch headphone amplifier supports up to 600ohm-headphone impedance with additional gain for in-ear monitors (IEMs)
  • Exclusive op-amp swap kit includes three op-amps and tool for easy tone tuning Celebrated MUSES op-amps deliver true-to-life musicality


Keeping the audiophile spirit and philosophy alive

Four years after the debut of Essence STX — the long-term holder of the number-one position in Head-Fi's Sound Cards segment, as voted by highly-satisfied users globally — ASUS remains committed to delivering ever better high-end sound cards to delight the most demanding audiophiles. Drawing on years of experience in developing Essence One, Essence STU and Essence III, Essence STX II delivers meticulous design, quintessential performance and profound musicality — elements that shape the spirit of the whole Essence Hi-Fi series.

Legendary audio quality that just got better

Industry-leading 124dB SNR

Essence STX II delivers industry-leading 124dB SNR audio clarity, a much-envied quality inherited from the revolutionary and widely-acclaimed Essence STX sound card — and up to 64 times (64X) better than typical onboard audio hardware. Headphone output reaches a fantastic 120dB SNR.

Ultra-low jitter

A high-precision clock is crucial to audiophiles. Integrated circuits are susceptible to heat and temperature changes, which is why Essence STX II includes a premium temperature-compensated crystal oscillator (TCXO) clock source. It is an ultra-accurate timing technology that ensures ultra-low jitter.

Clean and consistent power supply

Essence STX II uses a dedicated four-pin Molex power connection rather than drawing power from the expansion slot like other cards, and that means a cleaner supply of electricity. Optimized power delivery is further assured with high-fidelity low-dropout (LDO) regulators — unprecedented in the audio-card industry. As well, audiophile-appreciated WIMA® capacitors deliver balanced sound.

Celebrated MUSES op-amps

The profound musicality that Essence listeners expect is encapsulated by celebrated MUSES 8920 and MUSES 8820 op-amps, which deliver true-to-life tonality and spacious sound imaging



Impeccable headphone amplification

Top-notch headphone amplifier supports

The built-in headphone amplifier supports up to 600ohm impedance — so audiophiles can plug in the finest high-impedance headphones to enjoy the pure quality delivered by Essence STX II.


Exquisite headphone gain control

ASUS engineers have furnished Essence STX II with an additional gain control designed especially for high-sensitivity IEM headphones, allowing musicians and audio purists to use earpieces that channel audio output straight to the ear canal — isolating ambient noise for listening that requires undisturbed concentration.

Easily adjust the sound for your ears

Three swappable op-amp sockets

Essence STX II benefits from swappable op-amp sockets that allow users to create different timbres and tonal combinations.


Additional op-amp swap kit

Essence STX II even comes with a swap kit that includes three additional op-amps — two Texas Instruments LME49720s and one MUSES 8820 — and a clamp tool that makes it easy to remove the op-amp microchips.


Audio Interface PCI Express
Audio Performance Output Signal-to-Noise Ratio (A-Weighted) (Front-out) :
124 dB
Output Signal-to-Noise Ratio (A-Weighted) (Headphone-out) :
120 dB
Input Signal-to-Noise Ratio (A-Weighted) :
118 dB
Output THD+N at 1kHz (Front-out) :
>0.0003 %(-110 dB)
Output THD+N at 1kHz (Headphone-out) :
>0.001 %(-100 dB)
Frequency Response (-3dB, 16bit/44.1KHz input) :
10 Hz to 90 KHz
Output/Input Full-Scale Voltage :
Line output (RCA, 3.5) : 2 Vrms (5.65 Vp-p)
Headphone output : 7 Vrms ( Vp-p)
Chipset Audio Processor :ASUS AV100 High-Definition Sound Processor (Max. 192KHz/24bit)
Digital-to-analog Converter(DAC) TI Bur-Brown PCM1792A
Sample Rate and Resolution Analog Playback Sample Rate and Resolution :
44.1K/48K/96K/192KHz @ 16bit/24bit
Analog Recording Sample Rate and Resolution :
44.1K/48K/96K/192KHz @ 16bit/24bit
S/PDIF Digital Output :
44.1K/48K/96K/192KHz @ 16bit/24bit
ASIO Driver Support :
44.1K/48K/88.2K/96K/176.4K/192KHz @ 16bit/24bit
Connectivity Analog Output
1 x 6.3 mm jack (1/4") Headphone out
2 x RCA (Un-Balanced)
Analog Input
1 x 6.3 mm jack (1/4") (Line-in/ Mic-in combo)
1 x S/PDIF out (1 x Coaxial)
1 x Front-Panel Header
Special Features Dolby® Technologies : Dolby® Digital Live/Dolby® Headphone /Dolby® Virtual Speaker /Dolby® Pro-Logic II
Operating System Windows® 8.1 , 32bit/64bit
Windows® 8 , 32bit/64bit
Windows® 7 , 32bit/64bit
Windows® XP , 32bit/64bit
Accessories Op-amp swap kit x 1
3.5mm-to-RCA cable x 1
6.3mm-to-3.5mm adapter x 1
S/PDIF adapter x 1
Driver CD x 1
Quick start guide x 1
Dimensions 168 x 107 mm ( L x W )
Note Op-amp swap kit content:
1 x Needle-nose pliers
2 x LME49720
1 x MUSES8820

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Customer review

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Average customer rating

(from 8 customer reviews)
All Time (8)


I have owned a ST since the Essence first came out and I am delighted to say that it's just been getting better.
The original had pretty rubbish amps and replacing them was a must, but the provided amps with the STX II are much better.
You don't know how much you are missing until you listen to one of these cards.
Don't expect your hard drive to fill up with software. There isn't any. Well, apart from the control console. That just offering some basic choices and lots of digital surround options for your headphones, should you ant that. It all works great and is installed with a single piece of Asus software. I often find that the install fails from some folders so try moving it to another if you get an issue.
By the way, I would strongly recommend you get a pair of open-backed headphones for playing games. They make positioning enemies in games much easier. You don't need all that surround stuff at all!!!

Dave Fazackerley 2017-07-13

Superb !

Got this paired with some Beyerdynamic DT 770+880+990 Pro 250 Ohm's, Brilliant piece of kit !

Sound is clean with lots of power.


Dicehunter 2017-07-09

I already owned a decent soundcard (Creative X-Fi Titanium) and great speakers (Swan M200 MKIII). The difference between onboard sound and the Creative was incredible, but I was afraid going from one quality soundcard to another could be quite negligible.

I was wrong.

It's like my speakers have finally found their voice and I can appreciate their true value. I'm listening to songs I've heard a thousand times before and they sound brand new and crystal clear.

I turned everything up to maximum and listened to Disturbed's cover of The Sound of Silence and I nearly cried.

This soundcard is worth the money, and if you have quality speakers you're doing them a disservice by not getting it.

Note: I haven't bothered with that whole 'op-amp swap kit' thing. It looks far too confusing for me. Great for mega audiophiles but don't be put off by it: you can leave the pliers in the box and never have to worry about them.

nogoodreason 2016-02-06

The Best just got Better

I originally purchased an Essence ST which i have used for the past 3 years, on upgrading my PC i found my new motherboard, Rampage V Extreme had no PCI slot for it, although the on board sound is good, it's nothing like an Essence card.
In the end i had no choice but to buy this card which fits in the motherboard with a dedicated slot, i thought the ST was good but this blows me away, i love playing games but i also love listening to music at its best and this card creates an amazing sound stage, i eventually intend to purchase the Bose 2.1 speakers which retail around



built new rig... went mad... got Creative sound blaster z.... thought was ok......

then i bought some Senheisser G4me zero and reliesed this card is crap and bass sounds super heavy...

done research.. acquired STX 2.... much better, but you must play with the settings for a while to dial it in.. not complicated. people say the driver/ utility tool is horrible.. i think it works very well, just with out the coloured lights all over it ( like the kids like )

best internal card out there, as good as a DAC? dont know but i know i dont have to leave it on the side where things can bash it etc!


Highly recommended !!!!

What can I say Awesome sound card crystal clear sound, I have only a 2.0 speakers and using it though S/PDIF Coaxial out and the sounds amazing also listened to it through standard head phones, Awesome

Replaced this with Asus Xonar DG 5.1 PCI Sound Card and the difference is like night and day

You get what you pay for and you will hear the difference its a card for audiophile's who looking for the best



Have been using on board sound for several years now, I owned cheaper sound cards before and never really bothered taking any notice of the sound quality thinking that on board sound would just do... how wrong! I have been testing my new sound card over the past two days, I paired this with a set of Beyerdynamic mmx300 headphones, All I can say is WOW, the only way to really know how well this card performs is by using it then going back to on-board sound, the hefty price tag will then definitely seem worth the expense!! If you want elite sound, buy it, at least it's not like buying a graphics card where every year or two you need to upgrade, this is the final upgrade with regards to sound!! I don't actually know why you would need to buy anything more expensive than this for your PC, go ahead treat yourself, the chances of being disappointed are ridiculously slim :)


Best card u can buy

I've had this card about 2 months now a all i can say is wow ! The sounds this card produces is incredible, I'm using a beyerdynamic mmx300 headset which is also only a couple of months old, Amazing combo especially when it comes to gaming, I olay mostly arma 2 day z an what an advantage i feel i have over everyone else, U can things from a lot further away an it gives amazing positional acuracy, When listening to music all u need to do is going into asus control panel an adjust to what type of music ur listening to then be prepared to ger blown away ! Truly outstanding combo, Well worth the money, i used to a creative soundblaster z sound card an that is a gd card for the price but this card will blow ur socks off, Highly recommended !!!!


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