Asus Xonar U7 7.1 USB Soundcard and Headphone Amplifier

This is a fantastic DAC. It's small and doesn't feel particularly premium, but the audio quality is brilliant. Be sure to download the drivers from Asus' website and don't use the included disk. The U7 doesn't increase volume as much as some other DAC's, but it should be enough for most people - I'd guess it's 40-50% louder than what most motherboards can output to headphones. The volume slider on the unit works fine, but it's easier to just use the Windows system volume slider, which adjusts to reflect the U7's capabilities when in use. If no headphone, speakers or mic is plugged into the U7, Windows behaves as if the device doesn't exist. The Asus U7 driver is very small and discrete and doesn't have an equaliser, so it won't conflict with any audio software you use.