Creative Xmod

External stereo (2-channel) audio adapter with 3.5mm plugs for headphone out, line out and line in. Largish volume knob and controls for the "X-fi crystalizer" and "CMSS-3D" sound enhancements. The device is fully self-contained and needs no drivers: it even works as a standalone sound enhancer and volume control if provided with power through the USB port.

The built-in sound enhancers are debatable. I generally dislike artificial sound enhancers and use Genelec speakers in my home stereo system. My feeling is that the CMSS-3D compresses rock music too much and is tiring on the ears. The X-fi crystalizer on the other hand seems to bring out some nuances, especially in the treble register. The Techspot reviewers on the other hand liked the 3D and disliked the X-fi... :)

I bought this device mostly because my MacBook's built-in sound card exhibited an irritating hissing noise. Recently I had the Mac's motherboard replaced and the hissing problem went away, so I haven't really used the Xmod since then.

By the way, the volume knob works in discrete steps just like the volume keys built into Apple's keyboards. By pressing shift-option, you can get finer increments. :)