Walls - threads in this forum tend to go all over the place. Just roll with it. (tube pun intended
)
Jeff - I'll try to answer your question, but it's about as hard to express objectively as why one would prefer one set of speakers to another. Though really, I think the difference is a lot more subtle than that, but more apparent than the difference between amps with speakers; I think because of the lack of room involvement, it's easier to hear these subtleties with a good set of headphones. The difference between various sets of headphones, though, is definitely as much as you get between various speakers. But that's a whole other issue...
I can't say much about ss vs tubes, because just about all my experience with headphones so far has been with tube amps. That will change in a week or two and I'll re-address it then. I'll just say that the pattern of harmonic distortions in tube amp, some say are less "displeasing" to the ear than those in ss amp output, even if the measured THD in the tube amp is higher.
But for now, these are things I look for, that vary from amp to amp or tube to tube:
- obvious distortion. My headphones (and yours, the D5000) are low impedance, meaning relatively high current, and tubes don't necessarily produce a lot of current. This especially affects the low end where power requirements are greater. With some amps/tubes, you just can't drive the headphones to a reasonable volume, or if you do, you can clearly hear distortion.
- less obvious distortion. I mentioned that with my Jade, I can hear some odd overtones with certain demo tracks. I can't really explain it any better, nor what the origin is. That certainly shouldn't be there, dunno if it's just something weird about my tubes as they wear out, or what. Wasn't there with the Little Dot. The presence of this is a big part of my motivation to upgrade.
- detail. This encompasses dynamics, precision of imaging, and breadth of the soundstage - how "wide" the stereo separation seems. I have a theory that all these are connected, that imprecision in a poorer transducer will to some degree impart random noise/artifacts to the sound, making the left/right waveforms not match as precisely, and hence distorting and narrowing the stereo image. That is, with a poorer amp, the distinct sounds/instruments in the stereo image tend to be more clustered in the center. (This is true of speaker systems too, IMHO.) Headphone maniacs use a lot of different terms for this, but I believe they're all referring to this same basic phenomenon of dynamic detail: "air," "space," "clarity" ... because it's hard to put into words. But personally I hear it mainly in terms of imaging and soundstage, how clear and precise the location of sounds are in the stereo spread, and this is probably the biggest single feature I look for when I'm auditioning these things.
- frequency response. Especially at the high end, some tubes present a brighter sound than others. I don't know if this is RTA response per se, or simply a pattern of distortion that is more apparent in high frequencies... But it's the same thing as bright vs mellow speakers. Again maybe not as huge a difference as you can get between some speakers, but it's there, you can hear it easily enough. And some amps can't put out the power needed to drive the low end - like with the Little Dot, when bass is full and loud, the whole thing can get a bit distorted and mushy.
I think overall the type of sound details you look for in headphones is the same as with speakers. It's just that without the room to complicate things, there's a more direct link between the amp and what you hear through the headphones. This makes the search for a good amp more important, in my view, for headphones than for speakers.
Let me also point out that there's a HUGE variation in impedance between different types/brands of headphones, compared to speakers that vary only from about 4-8 ohm. For example, My Denons are 25 ohm, and a number of other brands like Grado tend to be low impedance. Some of the popular high-end cans around now are high impedance - Senn HD800 are 300 ohm, Beyer T1 are 600 ohm. I think this drives some of the headphone confusion, because it's hard to find an amp that works really well at both ends of this impedance spectrum. Low impedance requires more current, high impedance requires higher voltages. Not all amps can do both equally well.
