ASUS Xonar Essence STX

[PAGETITLE=Introduction][Top Ad] The quality of PC audio has made incredible strides within just the past few years. At a CES a few years ago, Dave Wilson of Wilson Audio wowed show-goers when he demonstrated his imposing $135,000 Alexandria X-2 high-end speakers hitched to thousands of dollars of audiophile amplification, and fed by... an iPod. The point of the demonstration was to show the improvement that speakers can make in a signal source that many golden-eared audiophiles would consider low-quality. Today, even audiophiles are beginning to take another look at PC audio, thanks to the rise of lossless audio codecs that make it possible to store bit-perfect music and play it back at high bit rates. The PC is one of the best places to enjoy great sound (by virtue of the amount of time spent there), but one of the most difficult places to create great sound. The "head-fi" crowd (that is, those who prefer to listen to high-end headphones) seem to have the high ground when it comes to enjoying great sound at their PCs, since headphones are designed to eliminate the listening space - with its obstacles and reflective boundaries - entirely. Audiophile headphones exist, sold by companies like Beyerdynamic, Stax, AudioTechnica, AKG, Ultrasone, and Sennheiser - that's no problem. The weak link in many PC audio systems, where headphones are concerned, is actually the quality of the host machine's audio hardware. As it turns out, most PC sound cards are poorly suited to drive headphones of the high-impedance variety, which use voice coils wound with smaller-diameter wire, in order to create a more powerful electric field. Looking at a headphone driver like a simple loudspeaker, this stronger field enables the voice coil to produce greater force on the diaphragm. This comes into play in high-frequency extension, where it becomes important to reverse the direction of the diaphragm very rapidly, and also in low-frequency output, where producing large diaphragm movements are essential to generating beefy bass. The math here is simple - power is equal to voltage-squared over resistance. As resistance is increased, power decreases linearly, but as voltage is increased, power increases exponentially. Connecting high-end audiophile headphones (with their higher working resistance) to your PC's sound card means that you'll be driving less voltage into your headphones. When we reviewed the Razer Barracuda and ASUS Xonar D2 audio cards, they represented the high-water mark of voltage output, at 5mVpp - five millivolts, peak-to-peak. However, even the Xonar D2 managed just 'decent' volume output from my reference Beyerdynamic DT 770 high-end headphones, which present a 250-ohm load - the earlier-reviewed Ultrasone HFI-700 headphones presented a much more manageable 75-ohm load. Until recently, anyone hoping to get great headphone audio at their PC would need to invest not only in a high-end sound card, but a separate amplifier to boost the output voltage in order to achieve meaningful output from their audiophile cans, but an all-in-one internal solution capable of driving high-end headphones easily had yet to materialize. Then ASUS unveiled a rare curiosity at Computex 2008, a sound card dedicated to stereo output, with a built-in two-channel headphone amp, called the Xonar StereoX. That card materialized early this year in a somewhat different form, as the ASUS Xonar Essence STX (with the STX perhaps referring to its forerunner's moniker). The Essence STX clarifies the product's audiophile targeting somewhat, and touts an incredible 124dB signal-to-noise ratio. The card loses its optical/coaxial digital input connection, but gains an additional quarter-inch input jack for analog audio input, and a metal EMI shield covering the upper half of the card containing the analog output stage. The focus of the Essence STX is in providing the very highest-end experience for stereo music, not delivering realistic surround-sound effects, but the question is this - will you really miss them? The sound cards that currently top the charts are all multichannel jobs - with the ability to output 5 or 7 full-range channels and a separate, dedicated LFE channel for feeding a subwoofer, as well as the ability to synthesize multichannel reverb effects that lend a sense of spaciousness to PC games. The Essence STX, on the other hand, lacks analog outputs for multichannel audio, though it supports multichannel output via its S/PDIF digital output. Does the Xonar Essence STX's stratospheric signal-to-noise ratio and onboard headphone amplifier really elevate the audiophile experience at your PC? Or is it only a curiosity in the overcrowded market for PC audio cards? We're about to find out. [PAGEBREAK][PAGETITLE=First Impressions] The ASUS Xonar STX comes in a box that's similar in design to the one that our Xonar D2 card came in. The front of the box swings upward to reveal the card, encased along with its accessories in a multi-level plastic (PET) shell. However, the design on the carton is a departure from the other Xonar cards we've seen thus far. The entire box is black, and a Chinese tiger figure is emblazoned on the front. It's the same marvelous packing job we saw with the Xonar D2, and the effect is no less meaningful here - we're being introduced to a top-class product. The products in ASUS' Xonar lineup have typically had excellent accessory bundles included with them - the Xonar D2, for example, included basic versions of popular multitrack audio recording software, a full set of adaptors, and even a short optical audio cable. The Xonar Essence STX bundle includes an adaptor from the card's mini-optical output jack to a Toslink connector (the type of digital connection on most home audio electronics) and an adaptor from the card's stereo RCA output jacks to a single 3.5mm stereo jack. The bundle also includes an instruction manual and a pair of poster-size pages that explain the significance of the tiger figure - it was discovered on a small chime that dates from ancient China, over 4000 years ago. Also included with the Xonar Essence STX's bundle is an elegantly-bound "Audio Precision Test Report", which was generated using laboratory-grade test instruments made by Audio Precision. The same instruments used to measure the Xonar Essence STX's performance characteristics are used in the testing of high-end audio electronics that feed multi-kilobuck audiophile systems; ASUS' goal here is clearly to establish the Xonar Essence STX sound card as a true high-end audio component. The AP test report contains test results for a golden sample card's analog inputs and outputs, which are representative of the best performance from a typical non-modified card. The Xonar Essence STX is a PCI Express 1x card, which means that like other PCI-E Xonars before it, it requires a 4-pin power connector. The card itself is built on a black PCB, and its upper half is shrouded by a black brushed-finish EMI shield, which also features the tiger figure from the front of the card's packaging. Together with the gold-plated connectors and the gold-colored capacitors on the card, it completes a styling motif that oozes panache and class. ASUS Xonar Essence XTC Specifications Audio Processor: ASUS AV100. Digital-to-Analog Converter: TI Burr-Brown PCM1792A (14bit, 127dB SNR) Bus Compatibility: PCI Express x1. Signal-to-Noise Ratio (SNR, A-Weighted): 124dB for front-out, 117dB for 600-ohms headphone-out, 118dB for line input. THD+N (Total Harmonic Distortion + Noise; @1kHz): Front-out: 0.00003% (-110dB); headphone-out: 0.001% (-100dB); line-in: 0.0002% (-113dB) Frequency Response:

ASUS Xonar Essence STX

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