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.