Verdict: A serious competitor for the X-Fi, but better for music than gaming.
The market for discrete sound cards was looking terminal a few years ago, but Creative's X-Fi series, with EAX 5 and a 24-bit Crystalizer enhancement system for poor-quality audio sources, revived people's interest. Asus now fancies a bite at the dedicated audio market with the Xonar D2. It's priced higher than Creative's £118 X-Fi Platinum Fatal1ty Champion Series card and, for that kind of money, it needs to be something special.
The Xonar is an attractive piece of hardware, covered almost entirely with a black, brushed-metal RF interference shield, which Asus claims improves signal quality by as much as 6dB. Looking at the markings on the Asus HD Audio Processing Unit, which is just visible underneath, the chip serial number (ML86G.06) implies that the Asus-branded audio processor is a C-Media Oxygen HD - a very capable chip. This is accompanied by a Burr-Brown PCM1796 Digital to Analogue Converter (DAC) and Cirrus Logic CS5381 Analogue to Digital Converter (ADC).
Thanks to the Oxygen HD hardware, the Xonar has sample rates of up to 192kHz, whereas Creative's X-Fi is capped at 96kHz, although this will be of most interest to audio professionals. The SNR is quoted at 118dB playback and 115dB recording. This places it above Creative's current mainstream X-Fi cards, and squarely in the territory of its flagship Elite Pro, which costs around £70 more than the Xonar D2 but includes a comprehensive breakout box. Dolby and DTS provide the full gamut of surround capabilities on the Xonar, including Dolby Digital Live, Dolby Headphone, Virtual Speaker and ProLogic IIx, plus DTS Connect. This is again superior to the X-Fi, which uses Multi-Speaker Surround-3D (CMSS-3D) but can't perform real-time AC3 encoding. The Xonar has this capability, so you can output your surround sound over S/PDIF to compatible speakers.
Asus also uses a neat S/PDIF arrangement that enables you to use the same in and out connections for either optical or coaxial digital connections. As a result, Asus manages to squeeze a very healthy array of connections on the Xonar, including microphone and line in, plus four dual-channel mini-jacks for analogue 7.1 audio output. A mini-MIDI jack sits on a separate backplate, and is linked to the card by a short cable.
Surround sound for gaming is one area in which the X-Fi remains dominant. The Xonar supports only EAX 2, whereas Creative's X-Fi cards offer EAX 5 in hardware. However, Vista distorts this, as it emulates DirectSound in software, rather than providing direct hardware acceleration as Windows XP does (through a hardware abstraction layer). Microsoft defends its decision by claiming that moving the audio driver from the kernel avoids instability from buggy audio drivers (although it also makes the implementation of DRM more robust). The upshot is that all EAX effects in Vista are disabled by default.
Fortunately, developers have been moving over to an alternative, OpenAL, and Creative is working on an ALchemy system (free to X-Fi users, $9.99 to Audigy owners), which translates EAX calls to OpenAL on the fly, although the list of supported titles is far from complete. However, while the Xonar supports OpenAL, Asus is clearly hoping that Vista will kill EAX, and that the Dolby Digital and DTS Connect of console games will come to the PC (through ports of console games in particular). However, as ALchemy is either free or requires a nominal payment, EAX probably won't die any time soon, so the Xonar could be a risky purchase if you're passionate about surround-sound gaming.
Aside from its Dolby capabilities and high-end audio specifications, the Xonar has another trick up its sleeve: Analogue Loopback Transformation (ALT). This provides a direct path from DAC to ADC, so you don't need to hook up the output to a line input with a cable in order to record. Although Asus stipulates that this should be used only for making legal backups of your own music collection, the technology would appear to be great for breaking DRM by making analogue backups at the best possible quality, using the supplied Portable Music Processor application.
To determine how all this stacks up in the real world, we put the Xonar through a series of music tests in which we played both high- and low-quality MP3s. We also tried a couple of games, particularly F.E.A.R., as this still uses DirectSound, plus Battlefield 2. We compared the results with those of Creative's top-of-the-range X-Fi Elite Pro. In the music tests, the Xonar fared surprisingly well, offering a fuller sound than the X-Fi, particularly in the mid-range. Under Windows XP, there was little between the two cards in F.E.A.R., with similar-sounding environmental effects.
However, the X-Fi offers 'X-Fi Mode' in Battefield 2, both in Windows XP and Vista. With the addition of ALchemy, the X-Fi was able to provide advanced environmental effects in Vista as well, while the Xonar sounded flat.
Conclusion
For the audiophile, Asus's Xonar D2 has the edge over Creative's X-Fi. However, its effectiveness for games revolves primarily around whether Dolby Digital and DTS Connect become common standards. At the moment, even though ALchemy is very much a work in progress, it hands the advantage to Creative with the current game generation, meaning the X-Fi is still the gamer's choice for the time being.
