The old U4 was a bit of a disappointment when it came to audio quality. The U5 is an improvement, but - despite Samsung's trumpeting of its DNSe 3.0 enhancement technology - not a vast one. The variant of DNSe used here is labelled ‘core', hinting that it doesn't offer the full power of the version used in the excellent YP-P3 player, and while it still features a processing enhancement designed to restore audio data lost through compression, along with a range of EQ settings, a bass boost function and a 3D effect, the overall result isn't nearly so impressive.
Bass response is very good, with the U5 dishing out a warm, well defined range of low-end tones and enough power that - with a half-decent pair of headphones - you won't want to use the bass enhancement function in anger, or you'll just get a nasty, booming mess.
The U5 is also a fine performer at the other end of the audio spectrum; you might find the highs slightly too bright for comfort, but there's plenty of detail. What's more, with the 3D effect kept low or switched off, there's a nice sense of space, with individual instruments clearly positioned across the stereo range.
The problems come with the mid-range. That all-important mid sounds slightly weak, thin and muffled, and that's enough to put the U5 behind the Sandisk Sansa Clip and even the iPod shuffle in the sound quality stakes. How serious this is will depend on the headphones you're using and the music you're listening to. The output actually seems quite well suited to the cheap and cheerful buds thrown in the box, though needless to say these won't satisfy anyone who is particular about audio quality.
I tried the U5 with a range of other ‘phones, including the Grado SR60s and iGrados, the Denon AHC551s and a set of Klipsch Custom 2s, and the weak mid-range was apparent across all of them.