Thee are very sensiive cans, infact they are much more sensitive than the pro 712, or hd 650, and lcd x, afaik, and I figure are much more revealing, and this might e whey your picking up noise, because of the high fidelity difference.
Id ont' know if it's possible for the headphones to introduce such a noise if they are damaged, i don't think so, but you might try to return the product if oyu think it si the unit, there is a significant massdrop an or manufacturer warranty. Have oyu tested with a difference source device, say a local powered separated battery powered mobile device, like say a mobile phone? Secondly, have you tried without the objective 2, why are you using an objective 2? Dos ti have better performance characteristics than the soundcard as an amp in thd and snr? To isolate the problem maybe try the on-board card, not through the pc case front port, but just right for the motherboard, and see if the problem persists, the k553 is so sensitive, it's probably fully powered by even your motherboard, or your sound-card, the 02 probably, you probably have too much gear in right now, how logn are oyur rca cables, what the capacitance and shielding characteristic, shielding so so important, but whichever device, make sure it's for 32ohm headphones.. it`s not the age for 32ohm gain, since k553, I would suggest the o2 is probably introducing problems, at lest i this setup, and that youe heapdhone have revealed them. momentum is nice but k553 is superior by far imo. yeah these phones are so sensitive, i dont think you have anything to gain by lining out to the obejctive two, besides maybe an analog attenuation stage. and you can possibly have enough headroom to attenutue after the soundcard amp as well, with an analog, after amp stage remote. does the 02 analog attenuate? i should hope so, anyhow, if you think you need amage, it' not so with this headphone, im sure you wont have any power related shortcommings using the soundcards internal amps, but we must wonder, what is the output imedance of that amp? does ti match for the k553. to high output impedance can maybe cause problem from headphone, that i where the 02 might be able to be useful in this case. maybe the card is only for high impedance cans? so, set oyur soundcard to heapdhone fer you remove the obejctive two, and for your mobo setting, ebfore oyu plug it in, otherwi you might be able to wreck equipment.. im not sure of your case.
on my reading for you, the card let you select output impedance, if you set this wrong, you cani probably wreck oyur equipment bad
you headphones need a very low output impedance setting, like a normal consumer load setting, to perform well. did you try o2 on battery and with gain switches? anyhow i'd say test fir tthe headphone with a mobile phone, if the probme isnt with the mobile phone, then the problem is elsewhere in the setup. if the problem is with the headphone, then maybe call for support to try a ne unit. just some suggestions to help.