I don't know... I'm looking info to upgrade my DAC/AMP to run a few headphones, not only the DT 1990 Pro. Maybe you can find info in it's thread, I think that lately some people where asking about there.
Sadly, my 1990 Pro is stucked somewhere in Spain, I ordered in Thomann Germany on april 9th and was shipped on 16th (they didn't have stock when I ordered), arrived to Spain on 19th and got stucked on 20th. I asked to Thomann to do something about and they answered that I have to wait 9-10 labour days since the last update, so tomorrow I'll email them again... I hope to get them next week.
(Last year, I had them for some months but sold to purchase T1.3 which I returned, and I miss the 1990s specially for metal)
Edit: Finally, they are here. I have missed them a lot for metal music... I've just listened to "Metallica - Black album" and right now "Tristania - World of glass", these are the best headphones that I've tried for the latter album: