Would the Oppo HA-2 sufficiently power a pair of HE400i headphones?
It'll get loud but I wouldn't really bet on it being as good as a desktop amp at the same price point.
Just wondering why the recommendation appears to be 400S over 400i.
Primarily because even just 3dB/1mW difference in sensitivity makes for a heck of a lot of difference. For example, with my D-Zero, which is a portable amp that I use as a back up, my 300ohm, 97dB/1mW HD600 gets louder cleaner (ie, stronger, cleaner bass) than the 62ohm, 93dB/1mW K70x. Given there isn't even a stark difference in the impedance between those HiFiMans, that means that you'd basically pour the same (if not higher) amount of power into the HE400S when it's already more efficient. It's not until I plug the AKGs into something like my Meier Cantate.2 that I can get them to sound as "dynamic" as Grados on a CMOY, whereas the HD600 isn't too far off with just the D-Zero.
Second, unless you're really looking for something that has a flat response from 1000hz down to 10hz, not everybody likes it. One reason why you get some people saying it has enough bass is because they can hear the low bass as well as therest of the bass range. Others feel the opposite way about them because they're looking for a bit of boost in the upper bass.
If you really prefer the response of the HE400i then go with that, but obviously it'll be farther off from the "dynamic" sense of presentation that Grados easily deliver (thanks to their high sensitivity).
I know the 400S is the preferred mobile recommendation but is there not a decent Mobile amp/dac that can power the 400i?
Not really "mobile," just
relatively more mobile than the HE400i - the HE400S after all is still an open back headphone.
Again the thing is you'd be able to pour the same amount of power (if not slightly higher) into the already more efficient HE400S. Basically, where the HE400i could use an Asgard, that same Schiit amp is already borderline overkill for the HE400S.
And then there's the other consideration: cost. If you're buying a desktop amp for $400 or so then might as well get the flatter response (if at least for half the graph) of the HE400i. But if we're talking portable DAC-HPamps you might as well save a bit of dought on that and use a more efficient headphone. Alternately, if you can drop enough cash on, say, an RSA Intruder or thereabouts, then the HE400i will work just fine.
Still, it might be enough for how loud you listen, so trying it with a portable isn't absolutely out of the question. We're just saying it's easier to get the most out of the HE400S. Even a Fiio E10K can do a lot with that, and that's USB powered.
