Manufacturer Asus Model Xonar DX Price (Street) $89.99 Availability Now I used to date a girl who was a little obsessive about what she ate. At every opportunity, she would buy fat-free, low-calorie, or otherwise diet derivatives of common food items. Now there’s nothing wrong with foods that are naturally fat-free or low in calories, but when you strip out the fat, salt, sugar, and delicious-but-carcinogenic chemicals, something is usually lost in the translation. Fat-free ice cream, for example, lacks the all-important creaminess that fat provides. Unsalted potato chips fall flat precisely because they lack salt. And Diet Coke, well, that just tastes wrong. Diet versions of existing products tend to be hollow representations of the originals, so we were understandably a little cautious when Asus announced its new Xonar DX sound card. The PC hardware giant stormed onto the sound card scene with the Xonar D2X just a few months ago, putting longtime market magnate Creative on notice. A $180 asking price put the D2X firmly in luxury territory, but with PCI Express connectivity, high quality components, innovative features, and useful bundled extras, it’s definitely worth the priceespecially when you consider the card’s solid gaming performance and exceptional sound quality. Asus’ new Xonar rings in at half the cost of the D2X, and the card itself is half the size. Naturally, then, the DX is missing some of the features and extras of its full-fat cousin. Keep reading to see how the diet Xonar fares without them. The Xonar, sans frills The Xonar DX differs from its D2X cousin in many ways, but some of those differences are more important than others. Take the audio chips used in each card, for example. The DX employs what’s marked as an Asus AV100 audio processor while the D2X uses an AV200. Don’t pay too much attention to the names silk-screened onto the chips, though; they’re the very same C-Media Oxygen HD audio processor under the hood. Asus says the chips go through a “quality sorting” process to separate the AV100s from the AV200s. Asus Xonar D2X Asus Xonar DX

Audio chip Asus AV200 Asus AV100

Digital-to-analog converter TI Burr Brown PCM1796 Cirrus Logic CS4398 (front)

Cirrus Logic CS4362A (center, rear, side)

Analog-to-digital converter Cirrus Logic CS5381 Cirrus Logic CS5361

Maximum recording quality 24-bit/192kHz 24-bit/192kHz

Maximum playback quality 24-bit/192kHz 24-bit/192kHz

Signal-to-noise rating 118dB 116dB (front)

112dB (center, rear, side)

Output channels 7.1 7.1

Multichannel digital output Dolby Digital Live, DTS Dolby Digital Live

Interface PCI Express x1 PCI Express x1

Street price $89.99 The Xonar DX’s AV100 audio processor may differ from the AV200 in name only, but that’s not the case with the card’s other onboard components. The DX uses a combination of Cirrus Logic CS4398 and CS4362A digital-to-analog converters to feed its analog output ports. The CS4398 is in charge of the card’s front output channels, and with a signal-to-noise rating of 120 dB, it’s the higher-quality of the two. Center, side, and rear channels are handled by a CS4362A chip that carries an SNR rating of only 114 dB. For reference, the TI Burr Brown DACs used for all of the Xonar D2X’s output channels carry a 123 dB SNR rating. Going in the opposite direction, from analog to digital, both Xonars feature ADCs from Cirrus Logic. The cards use different chips, though, with the DX featuring a CS5361 to the D2X’s CS5381. Signal-to-noise ratings once again favor the D2X. The CS5381 is rated for 120 dB, while the CS5361 has a rated 114 dB SNR. Individual parts specs are important, of course, but we’re more interested in the Xonar DX as a sound card. Asus pegs the card’s overall signal-to-noise rating at 116 dB for the front outputs and 112 dB for the rest. That’s reasonably close to the 118 dB SNR rating of the Xonar D2X, especially if you’re mostly going to be listening to stereo content. Despite differences in SNR, both cards support high-definition audio at up to 24 bits and 192kHz across all their inputs and outputs. Support for 192kHz recording is particularly notable because Creative’s X-Fis can only record at up to 96kHz. Like most modern sound cards, the Xonars feature 7.1 analog output channels. Their Oxygen HD audio chips are also capable of encoding Dolby Digital Live bitstreams in real time. Support for real-time Dolby Digital Live encoding is useful for folks who want to play games on multi-channel speakers using a digital output. Running multi-channel output through a single digital connection is much neater than using a bunch of analog cables, although you will need a compatible receiver or set of digital speakers capable of decoding a Dolby Digital Live signal. In addition its ability to encode DDL bitstreams on the fly, the Oxygen HD audio chip can also do real-time DTS Interactive encoding. This DTS encoding capability doesn’t make the cut for the Xonar DX, though; it’s only exposed in the pricier D2X model. DTS Interactive and Dolby Digital Live perform the same function, so the only thing the Xonar DX really loses here is compatibility with receivers or digital speakers that support the former but not the latter. While it’s not listed in the chart, we should note that the Xonar DX retains the D2X’s support for Dolby Headphone and Virtual Speaker, er, virtualization schemes that simulate 5.1-channel environments over stereo output. Dolby Pro-Logic IIx is also on the menu for those who want to up-mix stereo or 5.1-channel content for output across 6.1 or 7.1 channels. A creative approach to EAX support Perhaps the greatest weakness of the Oxygen HD audio chip used in the Xonar DX is its relatively pedestrian positional 3D audio credentials. The chip natively supports EAX 2.0a technology that dates back to the SoundBlaster Live! and is restricted to 32 concurrent 3D voices. Creative’s latest X-Fis can handle up to 128 concurrent 3D voices at higher definition sampling rates and resolutions. The X-Fi also performs positional audio calculations in hardware, while the Oxygen HD has to offload them to the host system’s CPU. The popularity of multi-core processors (and more importantly, games that leave multiple cores unused) has lessened the need for hardware-accelerated 3D audio, but there’s still a big gap between EAX 2.0 and 5.0. Asus bridges that gap with a software feature it calls DirectSound 3D GX 2.0, which is capable of emulating EAX 5.0 functionality that had previously only been available with Creative’s X-Fi cards. DS3D GX presents the Xonar as an EAX 5.0-compliant audio card, and then intercepts EAX calls, re-routing them to the Xonar’s own audio processing engine. That engine does its best to approximate EAX effects, and it can handle up to 128 concurrent 3D voices with enhanced reverb effects for “most” DirectSound 3D games. Positional audio calculations are still performed on the host system’s CPU, but DS3D GX at least brings the Xonar beyond EAX 2.0’s 32-voice limitation. Creative is quick to point out that DirectSound 3D GX doesn’t deliver “genuine” EAX 5.0 effects, and Asus readily admits as much. However, Asus also says users will be hard-pressed to tell the difference between the twoa claim we’ll explore when we dive into listening tests a little later in the review. Asus cites an additional advantage of its DS3D GX approach for Windows Vista users. Vista features an all-new Universal Audio Architecture (which you can read about in more detail in our initial look at the Xonar D2X) that removes the hardware abstraction layer for DirectSound 3D, effectively killing positional 3D audio in games that exclusively rely on DirectSound 3D and its EAX extensions. To work around the new audio stack, Creative offers an ALchemy software package that converts DirectSound 3D calls for processing by a third-party OpenAL API that still has direct access to audio hardware in Vista. Thus, at least in Vista, ALchemy performs a similar function to DirectSound 3D GX. However, ALchemy is a standalone application that must be specifically configured to work with different games. DS3D GX is built right into the Xonar’s drivers and doesn’t require additional software or game-specific profiles.

A Xonar, halved When we talked about Asus putting the Xonar on a diet for this new DX, we weren’t joking. The card really is quite a bit slimmer than its predecessors. Asus builds the DX on a half-height card that’s perfect for slimline enclosures that are too small for full-sized expansion cards. However, at 170mm long (roughly six and three quarters inches, if you’re an Imperialist), the card will require some open room behind your motherboard’s PCI Express x1 slot. Ah, yes. The Xonar DX features PCI Express connectivity, finally giving users something reasonable to plug into their motherboards’ x1 slots. The extra bandwidth afforded by the PCIe interface probably won’t do much for the card, but it’s certainly a more future-proof expansion standard than the older PCI interface, which seems destined to be largely phased out soon. The Xonar’s Oxygen HD audio chip wasn’t designed for PCI Express, so Asus uses a bridge chip from PLX to adapt it to the PCIe interface. This bridge chip appears to conflict with motherboards based on Nvidia’s latest nForce chipsets, though. We couldn’t get the Xonar detected in a motherboard based on the nForce 790i SLI reference design, with the Vista device manager reporting problems with a PCI-to-PCI Express bridge. The same problem also afflicts the Xonar D2X, and according to Nvidia, it’s a BIOS issue that will be resolved with an update shortly. We’ve spent most of our time so far discussing features that didn’t make the cut for the Xonar DX, but the card actually includes one perk that its full-fat counterparts lack: headers for front-panel audio connectors. Front-panel connectivity probably should have been included with the original Xonars, so it’s nice to see Asus bring it to the DX. With so little board real estate, it’s no surprise that a number of the DX’s components are mounted on the back of the card. You don’t get a fancy EMI shield like on the Xonar D2X, either. And despite its diminutive size, the DX still requires auxiliary power from a four-pin floppy connector. LED-backlit ports were probably one of our favorite features of the original Xonar, but since they’re a little more flash than function (at least unless you spend a lot of time swapping speakers), they didn’t make the cut for the Xonar DX. Instead, users are greeted with a standard array of analog input and output ports. If you prefer digital connections, the DX’s S/PDIF output is shared with its analog line and mic input port. A digital S/PDIF input port isn’t provided on the port cluster, but the card does feature a four-pin auxiliary input connector. Asus bundles the DX with an S/PDIF adapter that allows a standard TOS-Link cable to connect to the Xonar’s shared digital output port. A second mounting bracket is also provided for those looking to take advantage of the card’s low-profile proportions.

Game performance We’ll kick things off with a selection of four of the most recent PC games on the market, each based on an entirely different engine. All games were tested with Fraps, which logged frame rates as we played through 60-second sections of each title. Tests were run five times and the results averaged. We’ve also provided a look at how frame rates tracked through our 60-second gameplay run and the median low frame rate for each card. Display resolutions and in-game detail levels were chosen for each game with an eye towards delivering frame rates that we’d be happy playing with normally. These settings were maintained regardless of the audio card used. Bioshock

Bioshock uses Unreal technology, delivering native support for OpenAL in Windows Vista. DS3D GX didn’t work properly with Bioshock at first, and the game would fail to run with EAX enabled. However, Asus was able to quickly get us an updated .dll for the Xonar’s drivers that resolved the issue. The Xonar doesn’t deliver the highest frame rates in Bioshock, but it’s not far off the pace set by the X-Fi XtremeMusic. Call of Duty 4

Call of Duty 4 uses an engine of developer Infinity Ward’s own creation. In Windows Vista, audio is handled by OpenAL. Average frame rates are pretty close in Call of Duty 4. Given the variable nature of Frapsing real-world gameplay sessions, I wouldn’t worry about differences of only a couple of frames per second. Crysis Crytek’s latest engine is an absolute beast, and rather than relying on any form of hardware acceleration, it includes a software audio mixer designed to deliver the same listening experience regardless of the user’s sound card. Even with Crysis crunching positional 3D audio with a software mixer, the X-Fi manages the highest average and median low frame rates. The Xonar DX is right on its heels, though. Quake Wars id Software has long supported cross-platform APIs like OpenGL, so it’s no surprise that Quake Wars uses OpenAL under Windows Vista. The DX may finish at the bottom of the pile here, but frame rates are pretty close across the board.

Windows XP CPU utilization Since many enthusiasts have balked at moving to Windows Vista, we threw the cards through a quick round of CPU utilization tests in Windows XP. Here, we can enjoy the full benefits of DirectSound hardware acceleration without Vista’s Universal Audio Architecture getting in the way. The Xonar DX looks remarkably good here, managing lower CPU utilization than even the hardware-accelerated X-Fi. Something’s not quite right about these results, though. The Xonar D2X’s CPU utilization was much higher with a previous driver revision, and with DirectSound 3D GX offloading positional audio calculations onto the host CPU, it shouldn’t be using fewer CPU cycles than the X-Fi. Since the ability to encode multi-channel audio over S/PDIF is a key feature of the Xonar DX, we’ve run some RightMark 3D Sound tests with digital output. For these tests, the Xonar D2X, X-Fi XtremeMusic, and ALC889A were configured to pass DTS Interactive bitstreams. The Xonar DX can’t output DTS Interactive, so it was set to use Dolby Digital Live instead. Switching to multi-channel digital output doesn’t change the picture much. The ALC889A’s CPU utilization rises slightly, but the Xonar handles Dolby Digital Live with aplomb. Power consumption Power consumption has become a staple of our hardware coverage here at TR, but it’s not something we usually tackle with sound cards. Normal sound cards don’t come with auxiliary power connectors, though, so we busted out our Watts Up? Pro power meter and measured total system power consumption, sans monitor and speakers, at the wall outlet. Systems were tested at idle and again while playing an MP3. The Xonar DX consumes marginally less power than the D2X, and a little more than the X-Fi. Note that adding a discrete sound card doesn’t increase overall system power consumption by all that much over integrated motherboard audio.

Listening tests For many, the most important attribute of a sound card is how it sounds. To test that, I called in some favors with a couple of friends, subjecting them to music playback listening tests in the Benchmarking Sweatshop. These were blind tests, with the listeners unaware of which card they were listening to at any given time. To highlight the differences between cards, 30-second song clips were played back-to-back on different configurations using Abit’s iDome speakers connected via analog output. The Xonar DX was pitted against the D2X, X-Fi XtremeMusic, and ALC889 in head-to-head matchups with each song clip, and the order of playback was randomized for each song. This first set of listening tests examines CD-quality audio playback. We used uncompressed WAV audio ripped directly from source CDs and played them back in Windows Media Player 11. Below, you’ll find a summary of our listeners’ impressions of how the DX compared with its competition. I’ve also injected a few thoughts of my own, although since I was running the tests, I knew which cards we were hearing. Nine Inch Nails – Capital G (Epworth Phones remix) Nine Inch Nails goes disco with a bass-heavy Capital G version from the Y34RZ3R0R3M1X3D remix album. Yeah, Trent Reznor’s pretty 1337. Our listeners detected little difference between the Xonar DX and D2X on this track. However, both preferred the DX to the X-Fi. One listener commented that the DX delivered much richer bass with “mahogany overtones,” whatever that means. The other found that the DX offered much fuller vocals and deeper bass than the X-Fi. The ALC889A was clearly outmatched by the Xonar here, with both listeners describing the Realtek codec’s playback as muddled and much poorer than that of the DX. It was almost as if the almighty Realtek crab were overwhelmed by the song’s pounding bass line, causing it to lose focus on other elements of the track. Amy Winehouse – He Can Only Hold Her While perhaps not her most ironic performance of the year, Amy Winehouse’s He Can Only Hold Her spreads soulful vocals across a groovy drum line with hits of plucky piano and background singing. Again, the Xonar DX fared well against the D2X. Our listeners were quick to praise both, although one thought that the track’s piano elements sounded slightly better on the D2X. When pitted against the X-Fi, the Xonar did a much better job balancing the track’s vocal and instrumental elements. Both listeners found the X-Fi’s background content a little muffled behind the song’s strong foreground vocals. Integrated audio has come a long way in the last couple of years, but our listeners preferred the Xonar DX over our motherboard’s ALC889A codec. Both said the Xonar offered richer playback with fuller vocals, and I thought the piano in particular sounded much better on the Asus card. U2 – Original of the Species The Edge’s unmistakable guitar notes play off Bono’s trademark soaring vocals in this recent example of the pop rock formula at its best. One of our listeners found the Xonar D2X’s vocals a little fuller than those of the DX, but the other couldn’t tell the difference between the two. However, both agreed that the DX sounded better than the X-Fi. The vocal bias common on Creative cards was particularly obvious here, with the Xonar’s background instrumentals coming through just that little bit clearer. Differences between the DX and X-Fi weren’t nearly as great as between the Asus card and the Realtek codec. Our listeners weren’t impressed with the ALC889A, saying that its vocals sounded like “bad karaoke” next to the Xonar. They also thought the DX did a much better job with instrumentals and that the card sounded much more like a live performance. Johnny Cash – I Won’t Back Down The Man in Black channels Tom Petty, with Cash’s baritone backed up by acoustic guitar, piano, and even a little help from the heartbreaker. There are plenty of technical differences between the Xonar D2X and DX, but our listeners didn’t prefer one over the other with this song. They did, however, think that the X-Fi sounded a little better than the DX here. The XtremeMusic’s vocal bias served it well on this track, which has little background content to balance with the main event. Even with a relatively simple song, our listeners were quick to find fault with the ALC889A after hearing it played next to the Xonar DX. The Realtek codec lacked the sharpness of the Xonar, they said, and I thought it lost a little of the depth in Cash’s voice. Jet – Are You Gonna be my Girl? Iggy Pop meets AC/DC in this upbeat track, which mixes raspy vocals with guitar, drums, and even a little tambourine. The Xonars like to rock, and our listeners both thought they sounded great here. One did say the DX sounded just slightly better, but couldn’t say why. Both were in agreement that the X-Fi fell a little flat when compared with the Xonar, with one commenting that the DX was like having front row seats while the XtremeMusic put him up in the balcony. Interestingly, our listeners were a little less harsh on the ALC889A, although both agreed that it didn’t sound as good as the Xonar DX. The Xonar had better clarity, they said, and I thought the drum line was much punchier on the Asus card. Game time: DS3D GX under the microscope Asus claims that the Xonar’s DirectSound 3D GX’s EAX 5.0 emulation produces output comparable to true EAX implementations, so we just had to take it for a spin. We even contacted Creative to see if they could suggest some games that might highlight DS3D GX’s limitations, but the company’s few suggestions were dominated by games based on the older Doom 3 engine. EAX support just isn’t what it used to be, I guess. Creative did suggest that we try Bioshock, and since we had a few initial DS3D GX problems with the game, it made the cut. We also decided to throw a little Battlefield 2 into the mix. The game has a special X-Fi audio mode, and we were curious to see how that would pan out with the Xonar. I spent a couple of hours playing each game on the X-Fi XtremeMusic and Xonar DX with configured for 5.1-channel analog output with in-game EAX effects enabled. Surprisingly, Battlefield 2 let me invoke the X-Fi audio mode with the Xonar DX. After an afternoon of gaming, I came away quite impressed with DirectSound 3D GX. Creative may be correct in saying that it doesn’t deliver a genuine EAX 5.0 experience, and I wouldn’t be surprised if its emulation isn’t an exact 1:1 replica of EAX effects. But that didn’t diminish my gaming experience in the least. Bioshock is packed with aural ambiance, and the underwater city of Rapture was every bit as creepy with the Xonar as it was with the X-Fi. I couldn’t detect any difference between the cards in Battlefield 2, either, even in intense firefights loaded with explosions, gunfire, and frantic cries for a medic.

RightMark Audio Analyzer – Loopback – 16-bit/44.1kHz Moving from subjective listening tests to something more objective, we used RightMark Audio Analyzer to evaluate output quality. Our first set of RMAA results are from “loopback” tests that route a sound card’s output through its line input. We’ll kick things off with 16-bit/44.1kHz CD-quality audio. To keep things simple, I’ve translated RightMark’s word-based quality scale to numbers. Higher scores reflect better audio quality, and the scale tops out at 6, which corresponds to an “Excellent” rating. The Xonar DX is at least as good as the D2X here, which puts it right at the top of the field and easily ahead of the X-Fi and ALC889A. In fact, the DX actually scores better than its higher-priced cousin in the dynamic range test. The X-Fi appears to have some frequency response issues with RightMark Audio Analyzer’s loopback test in Windows Vista. You can read more about them here. Update 4/11/2008 — It turns out that the X-Fi requires some additional Vista driver tweaking to work correctly with RightMark Audio Analyzer. We’ve re-tested the XtremeMusic with Creative’s updated settings and added those results to the review.

RightMark Audio Analyzer – Loopback – 24-bit/48kHz My Nine Inch Nails With Teeth dual disc’s DVD-Audio tracks are 24-bit/48kHz, and we ran RMAA at that bitrate and resolution. The Xonars continue to hang together as we crank up the sampling rate and resolution. Although the X-Fi is more competitive here, it still doesn’t score as highly as the DX.

RightMark Audio Analyzer – Loopback – 24-bit/96kHz 24-bit/96kHz is as good as multi-channel DVD-Audio gets, so we’ll test at this bitrate and resolution, too. The Xonar DX makes 24 bits at 96kHz look easy. Note that our integrated motherboard audio again delivers the lowest scores in these objective signal quality tests.

RightMark Audio Analyzer – Loopback – 24-bit/192kHz Stereo DVD-Audio goes up to 24 bits at 192kHz, so we tested that resolution and bitrate, too. Since the X-Fi doesn’t support 192kHz recording, we were unable to run loopback tests on the XtremeMusic at this sampling rate. Even with the sampling rate cranked to 192kHz, the Xonar DX goes toe-to-toe with the D2X.

RightMark Audio Analyzer – Playback – 16-bit/44.1kHz To remove each sound card’s line input as a variable, we switched from RMAA loopback to straight playback tests using an X-Fi Fatal1ty installed on a separate system for recording. The X-Fi doesn’t support 192kHz recording, so our playback tests only scale up to 96kHz. Xonar dominance extends to our RMAA playback tests, where the DX and D2X are again closely matched. The X-Fi and ALC889A lag behind in almost every test.

RightMark Audio Analyzer – Playback – 24-bit/48kHz The XtremeMusic seems to fare better with 24-bit audio than it does at 16 bits, but even then, it can’t entirely match the signal quality offered by the Xonar DX.

RightMark Audio Analyzer – Playback – 24-bit/96kHz The fact that the Xonar DX manages to keep up with the more expensive D2X throughout our RMAA signal quality tests is nothing short of impressive.

Detailed RMAA results – Loopback – 16-bit/44.1kHz If you want to geek out over a bunch of detailed RMAA graphs, we’ve provided the raw results for all of our RMAA tests over the following six pages. These results are included as a bonus; feel free to skip to the conclusion, if you wish. Stereo Crosstalk Dynamic Range Frequency Response Intermodulation Distortion Noise Levels Total Harmonic Distortion

Detailed RMAA results – Loopback – 24-bit/48kHz Stereo Crosstalk Dynamic Range Frequency Response Intermodulation Distortion Noise Levels Total Harmonic Distortion

Detailed RMAA results – Loopback – 24-bit/96kHz Stereo Crosstalk Dynamic Range Frequency Response Intermodulation Distortion Noise Levels Total Harmonic Distortion

Detailed RMAA results – Loopback – 24-bit/192kHz Stereo Crosstalk Dynamic Range Frequency Response Intermodulation Distortion Noise Levels Total Harmonic Distortion

Detailed RMAA results – Playback – 16-bit/44.1kHz Stereo Crosstalk Dynamic Range Frequency Response Intermodulation Distortion Noise Levels Total Harmonic Distortion

Detailed RMAA results – Playback – 24-bit/48kHz Stereo Crosstalk Dynamic Range Frequency Response Intermodulation Distortion Noise Levels Total Harmonic Distortion

Detailed RMAA results – Playback – 24-bit/96kHz Stereo Crosstalk Dynamic Range Frequency Response Intermodulation Distortion Noise Levels Total Harmonic Distortion