I've owned a pair of AH-D550s since at least 1997, although I don't listen to them anymore (so this review is from memory, please take it as such).

For quite a long time, I used my pair to both listen to music and edit digital music files on my PC. Most of this time, I used them unamped directly from the soundcard and they were fine being driven this way.

This headphone reminds me of the Sony V6 in its sonic signature. There's nothing hi-fi about it, but it's a good "work can" for doing the type of stuff I was doing, and great for some casual music listening as well. They're not all that portable, and are more of a studio-type headphone.

If you've heard the Sony V6, you basically know what these cans sound like -- a consumer-level "V-curve" balance with pretty enhanced bass/highs, and not much to talk about in the way of mids.

Knowing what I do now, I would not recommend the AH-D550. Denon has cancelled most of their headphone lineup, except for this one (which is why I decided to put in a review, being that they're still available). They don't cost much, so whether or not you take the gamble is up to you. Personally, I felt they sounded better than Grado SR-60, but I'm not a Grado fan in any way. OK for casual listening, but for critical listening please look elsewhere.

P.S. they do isolate a little (semi-closed design), so not too bad a choice for working/listening at the computer if the fans aren't too loud.