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Asus Xonar Essence STX Sound Card Review

Asus Xonar Essence STX Sound Card
“It isn't the ideal sound card for everyone's needs, but it's an absolutely splendid solution for music lovers.”
  • Produces exquisitely clean audio
  • thanks to the presence of high-end components and meticulous attention to electrical design.
  • Surround-sound output is limited to digital; not a good solution for Blu-ray movies.


If you’re the type of audio enthusiast who delights in discovering nuances in musical recordings you thought you were already intimately familiar with, you’ll want to check out the Asus Xonar Essence STX sound card. This audiophile-quality sound card is a glittering sonic jewel.

If you’re the type who thinks MP3s encoded at 128Kb/sec sound just fine, on the other hand, no amount of praise we heap on the Xonar Essence will ever convince you that this card easily justifies its $180 street price—especially when even the least expensive computer can play music without needing any additional hardware at all.

But have you ever plugged a pair of quality headphones into your PC’s onboard audio and really listened to it? The interior of a PC is a harsh environment for audio, and most onboard sound systems do little to compensate for it. Listen carefully and you’ll hear noise and distortion worming its way into your music, irrevocably changing and diminishing what the artist worked so hard to record.

It doesn’t have to be that way. A PC can be an awesome high-fidelity component, and the Xonar Essence STX is proof. This card boasts very high-end digital and analog audio components, and it’s been vigorously engineered to eliminate the noise problems that plague the typical onboard audio solution. The result is the cleanest sounding PC soundcard we’ve laid ears on.

Features and Design

Asus uses a Burr-Brown PCM1792A digital-to-analog converter (DAC) that delivers up to 24-bits of resolution and sampling rates as high as 192kHz. Of course, if you examine the specs for the onboard audio solutions used in most PCs these days, you’ll see the same numbers, so we have to look deeper for an explanation as to why this card sounds so delightful.

The answers are to be found in some of the card’s other specs, such as its signal-to-noise ratio, a measurement of the relationship between the strength of the desired signal and unwanted background noise (e.g., hum, hiss, and static). Everything else being equal, the higher the number the better, and the Xonar Essence STX’s numbers are very high indeed. Where the typical motherboard audio system delivers signal-to-noise ratio in the mid 80s, Asus claims its card delivers a signal-to-noise ratio of 124dB when driving speakers, and 117dB when driving headphones.

The Xonar Essence STX’s other specs are equally impressive, putting it in the range of pro audio gear: Broad dynamic range of 118dB, for instance, enables the card to more accurately reproduce the diversity of instrumental and vocal timbres that make great recordings so rich, full, and rewarding. And total harmonic distortion (THD) of just 0.0002 percent means that the music is all you hear. This is largely due to the use of effective shielding to stop electromagnetic interference from bleeding into the analog signal path.

Another feature that renders this sound card unique is the presence of an onboard headphone amplifier (the well-regarded Texas Instruments TPA6120A2 chip), coupled with software that lets you adjust the amount of gain for headphones that present different amounts of impedance, ranging from 0dB gain for headphones with less than 64 ohms of impedance (most consumer models fall into this category), to 12dB gain for headphones with 64- to 300 ohms of impedance, and 18dB gain for professional phones with 300 to 600 ohms of impedance.

The software does a lot of other things, too. You’ll find a host of environmental effects (concert hall, stadium, and the like), a programmable equalizer, and several DSP modes, including Dolby Virtual Speaker, Dolby Headphone, and Dolby Pro Logic IIx. We don’t find much joy in folding, spindling, and mutilating our favorite tunes, however, so we didn’t spend a lot of time with these geegaws.

The card is equipped with an output header you can connect your case’s front-panel mic and headphone jacks, and an input header you can connect to an internal TV tuner or other audio source. Unlike most sound cards, the Xonar Essence STX eschews 1/8-inch connectors on its mounting bracket in favor of more robust 1/4-inch headphone-out, 1/4-inch line- or Mic-in, and stereo line-level RCA outputs. There’s also a combo coaxial/optical S/PDIF output, which is the only means of routing surround sound to an A/V receiver or speakers. Your outboard gear must therefore be outfitted with a DAC and a Dolby Digital decoder. The only feature lacking, in our view, is an RIAA phonograph pre-amp for connecting a turntable.

Asus Xonar Essence STX Sound Card

Asus Xonar Essence STX Sound Card


But enough about integrated circuits and specs. How does this card sound in a real-world listening test? In two words, freakin’ awesome. We tested the card listening to audio CDs ripped and encoded using the FLAC lossless codec on good-quality headphones (Sennheiser’s HD-555), high-end noise-isolating earbuds (Shure’s SE530), and two near-field sound systems: TBI Audio System’s Majestic Diamond 1R audio monitors (driven by that same company’s Millenia MG3 amplifier) and Focal JMlabs’ self-powered Focal XS 2.1-channel speaker system.

Asus Xonar Essence STX Sound Card We chose a diverse range of music that we’ve become intimately familiar with after many years. Listening to Steely Dan’s “Josie,” from the group’s eponymous Aja release, we were impressed with the card’s ability to distinctly render each voice and instrument, whether it was Walter Becker’s jangly guitar licks or percussionist Jim Keltner dragging his drumstick across the wind chimes. We had similar experiences with a host of other tracks, ranging from Paul Thorn’s “Sister Ruby’s House of Prayer (from his divinely irreverent CD Mission Temple Fireworks Stand) to Robert Plant’s and Alison Krauss’s haunting cover of Tom Waits’ “Trampled Rose,” from their collaboration Raising Sand.

The Xonar Essence STX makes a good gaming card, too, thanks to its support for positional audio engines and APIs, including DirectSound3D, A3D, and OpenAL. The card cannot, however, deliver genuine support for Creative’s EAX environmental audio effects (it intercepts a game’s EAX calls and redirects them its own audio-processing engine). And the fact that its surround-sound output is limited to digital audio complicates its compatibility with gaming-oriented speaker systems, which typically rely on analog audio connections. Blu-ray fans will likewise want a card that’s capable of routing six channels of analog surround sound to an A/V receiver or speaker system; or better yet, transporting that disc format’s Dolby TrueHD or DTS-HD soundtracks over an HDMI cable to a decoder.


When all is said and done, the Xonar Essence STX isn’t the ideal sound card for everyone’s needs, but it’s an absolutely splendid solution for music lovers. And we much prefer a purpose-built system that excels at one job over a jack-of-all-trades solution that’s inferior on several counts.


  • High-end DAC
  • High-quality integrated headphone amp
  • Extremely quiet
  • Exquisite sound


  • Pricey
  • Surround-sound output is digital only
  • Not a great Blu-ray solution
  • No RIAA phono pre-amp

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