Quote:
Originally Posted by
LostArk 
I'm a stereo guy, not a headphone guy, but I'm guessing the same principles hold true as in the stereo world: speakers (headphones) sound different, not amps. I'm also guessing there's a magical thinking fringe who insist amps make more than a negligible difference.
The "magical thinking" people are the ones who insist that amps can measure the same across the board but still sound different. (There are a lot of people who really do believe that, and they're generally the same ones who poop on DBT's.) However, amps that measure very differently are likely to sound quite different as well...and that's very relevant in the headphone world, where few amps are designed objectively according to measurements. (A couple DIY projects like the O2 and The Wire are, and some very expensive amps like Violectrics also measure well.) Instead, a lot of amps are designed subjectively by ear, so they will have colored frequency responses, varying levels of output impedance, significantly different square waves and slew rates, and vastly different amounts of total harmonic distortion, intermodular distortion, noise, phase shift, etc. There are a lot of people who swear by tube amps, which are generally designed in a way that creates euphonic harmonic distortion.
All of that leads to a lot of significantly colored amps, and it doesn't even cover the question of whether an amp can output enough voltage and current to satisfy a particular pair of headphones. In your case, I seriously doubt the MCD500's output power was lacking, though I don't know its actual specs. I also don't know its output impedance, and a high output impedance would adversely affect the SR325i more than the DT770-80, but it would affect the HD650 the least...and you still disliked them.
The MCD500's other characteristics (if any) may or may not have exacerbated the flaws of the headphones you listened to, but there's not really any evidence that it affected your preference: You basically criticized the Grados and Sennheisers for opposite flaws (whereas the DT770 is more of a happy medium to you), and a strongly colored amp would have likely pushed all of the headphones in the same direction together. Plus, your criticisms of the SR325i and HD650 line up perfectly with common criticisms of those same models.
You might like the DT770's better due to familiarity bias...or maybe their sound signature is just better suited to you. Pretty much all Grados are commonly referred to as harsh, shrill, and piercing, and the HD650's and HD600's are commonly criticized for an apparent "veil" (or muddiness, which is probably a much stronger term than most would use). The DT770-80 is often criticized for boomy bass (unlike Grado), but its frequency response also emphasizes the highs to balance that out, so it's perfectly reasonable to believe it's your genuine preference. The DT990 could be roughly characterized as an open alternative to the DT770 with less isolation, but if you're looking for a similar sound signature with more soundstage in a Beyer model, the owner's thread for that might be a good place to investigate.
Edited by SobbingWallet - 12/1/11 at 5:12pm
