Kindly ensure that the headphones are connected to the second from the right port dedicated for the headphones and headphone connector is fully inserted in the port.
Also ensure that there are no problems on the software side (latest driver installed etc) because what you are describing cannot be possible unless there is a problem with something. If you still have your creative Fatal1ty Titanium card then try to see if the volume levels of DT770 remain the same with both cards. Also try some different headphones with both soundcards to identify the problem.
Bro I had already connected to the correct port and installed the latest drivers, but sound still felt muffled outside the box. Now the sound is fine. I went to speaker/headphones settings and set them to default, then changed them again to the desired settings. Sound became fine then. Master volume is still kept at 80, but I can hear plenty from low volume on winamp. Sound is crisp and clear. I don't know, might also be because I was used to listening on my monitor speakers, or maybe these cans required some burn in time.
There is just one other issue. When I play
this music at higher volumes, there's a crackling noise with the bass. I guess these cans can't handle that much power. Even though the sound is not that high to blow my brains out. On normal volume the sound is fine though with clear deep bass.
https://www.youtube.com/watch?v=8b-FEaGJG8Y
Update: Okay so I just played Battlefield 4 while using these headphones and the same crackling noise is coming with explosion sounds. And that too at normal volume! I doubt these headphones aren't capable of handling such levels of sound. Something is definitely wrong.
I listened to that music track on my old Sennheiser HD 202 (connected to the amp port of the soundcard) at max volume, both master and of winamp. There was no crackling noise on those. So I think the problem is with the DT 770. I've emailed their support. Waiting for their response now.
Update 2: Tested the DT 770 on my older card Fatal1ty Pro and the crackling noise is still there so it confirms the problem in the headphones. I'm sending them for RMA.
Update 3: Just ran the
bass frequency test and it double confirmed the fault. So much clipping/crackling especially on lower frequencies. This wasn't the case on my old HD 202. Damn defective piece!