Originally Posted by MuppetFace
Can't speak for morbidtoaster, but to me the Leben is on the tubey side of the spectrum. The TH900 is a very meticulously balanced transducer, teetering on the edge of excess for me at times. It's like a tower of blocks threatening to tip over at any time (but generally doesn't) if that makes sense.
Pairing it with something upstream that has its own very distinct coloration can upset that balance. The Leben pushes it over the edge: it becomes swollen, slower. IMHO the TH900 is best paired with an amp that is on the faster and more transparent side of things. With the ZDSE, there's just the faintest hint of euphony to add a flourish; I find it accentuates what's already there, basically buttressing the TH900.
At first, I thought the TH900 was not so picky about amping, and I was both right and wrong.
It has a high sensitivity of 100 dB/mW, so it can be driven by virtually anything including an iPod, whereas less efficient orthos need more pack n' punch of power.
However, having less demand for power alone doesn't necessarily make it an easy headphone to drive, or as I should put it, a headphone that sounds right with all amps. There are subliminal aspects that are often overlooked, such as balancing the sound signature. With a headphone like the TH900, I found that while many amps sounded good, it was rather difficult to find an amp that could truly "wow" me. Plus, the low impedance of the TH900 (25 ohms) render many vacuum tube amps poor choices, unless they have a very low output impedance like the Zana Deux SE.