Finally got my U3 last night after a UPS screw up and it taking an extra ~3 weeks to deliver.
These were tested with my 600ohm DT990's. I am not expecting this to drive these exceptionally well for music. This was bought purely for gaming on my gaming laptop. I have another setup for movies and music.
Right out of the box, using it for Dolby Headphone blows away the THX TruStudio Pro Surround that comes on my laptop's sound card. I have used Dolby Headphone before on my desktop via an ASUS sound card, and have used Yamaha's Silent cinema via my receiver. This is by far the best option I've heard for gaming. Despite the fact that Dolby Headphone should be Dolby Headphone, this implementation seemed to have less audio timbre distortion that the one on my previous sound card. The THX flavor, which is now replacing Dolby Headphone on creative cards, is great for movies, but horrible at placing rear/side sounds in games. It does a great job of preserving the sound quality however. I used Left 4 Dead 2 to test positioning as it one of the better games I own for sound placement.
The Dolby Headphone settings let you pick between DH-1, DH-2, and DH-3. DH-1 is the "reference room" seems the best for gaming. The sounds seems almost clinically places in the sound stage, and very easy to pin point. I liked DH-2 for movies, and single player games for the "home theater" feel. There is more crossfade between the virtual 5/1/7.1 channels, and a tad more echo/reverb feels DH-3 is a little over the top for me, and only seems like it would be good to replicate an arena concert or music hall feel. Maybe some types of 5.1/7.1 encoded music would work here.
There was a gain option in the control panel. These were marked <32ohm, 32-64ohm, and >64 ohm. The 32-64 ohm setting more or less replicated the volume level of my laptop's built in card. With it set to the >64 ohm setting, I could drop the volume to 70% and still have the same output as my laptop built in with the volume maxed. Maxing the volume on the highest gain didn't produce ear bleeding levels, but restored the volume controls usefulness to me. Previously, I had to max the volume settings to get workable output, and still felt something lacking in a few games (notably New Vegas). Now, I have a comfortable range to trim up or down with a little headroom. I didn't notice any clipping when I maxed the volume and gain and played some music for a bit, but I wasn't especially trying to find some ear bleeding song's either.
Nothing was obviously lacking in the sound, but I certainly don't have a golden ear. Using a 600 ohm set of headphones, I was not expecting the sound to get "thin" as my phones don't need much current at all to drive well. I was expecting the voltage swing to be a little lacking, and to some level, it is. This doesn't compare to my E9 or even a 2x9v cmoy for that. That said, for my gaming setup, it's a huge improvement over my built in sound card, both the processing and the output.
