About the song, I liked : Linkin Park - Meteora - Somewhere I Belong, but when I listen to this now, it starts fine till 23rd second when guitars,basses etc. comes in. This part is just terrible to listen to. It's all kind of "mixed together" just don't like it at all now :( . Maybe it should be like this, I don't know, didn't hear them live.
I didn't know this is one of the tracks you were using - I'd hazard a guess the source files are the problem, not necessarily your hardware. Linkin Park's recordings are too far from being reference-grade, and its not just because it isn't acoustic music.
For electric guitar music you can try Dream Theater, as well as Nightwish's Wishmaster, Century Child, and Once, for starters (avoid the non-remastered Angels Fall First), some of the songs have two guitars in the recording. For harder music with two guitars audible in most songs, try Epica, particularly The Phantom Agony (the whole album), Metallica (haven't listened much to their work after Reload so I wouldn't know about those) and Megadeath.
Look up the blurb on Schiit's amps, particularly the Valhalla - that's a great illustration of what the stereotypical tube sound is like. For amps that's mostly for OTL; some other circuit designs even with tubes can sound very different.
It means that any component of your system prior to the K701 - such as sources which tend to have a sound signature, and even certain amp circuits most pronounced if "cheap" (ie, compromises made for cost) or outright badly designed - will sound different, affect each other differently, and ultimately the K701 will reveal all of that more than other headphones within the same price range. A tube therefore will always add coloration (see above) and the K701 will let you hear that even if it's on the source (try adding just a tube buffer instead of a completely different source, for example). Also tendency is for solid state to have more current, which is what the K701 needs to bring out its dynamic range, so preferably have the tubes in the source or the preamp section of the headphone amp (or both), not in the driver circuit of the amp. Of course there are tube amps that perform well however they might turn out to be a bit expensive - even the LD MkII had dynamics but the notes were a bit too rounded and soft to me.
From my listening the NOS DACs I've tried are pretty clean compared to some other affordable oversampling units. Even the basic USB DACs I've tried tend to be a bit smoother (some HLLY dac-amp I had before, and the one in my Cantate.2) against even the SACD-compatible affordable DVDPs (which actually use OS DACs, not true DSD 1-bits) and some entry level CDPs. Tubes by measurement always add distortion but if its mostly harmonic I don't see any harm to it.
Edited by ProtegeManiac - 11/20/12 at 5:14pm