AMR DP-777, what am I missing ?

@knownothing I just use a generic USB cable for now.

I tested a 200$ USB cable (audioquest) I think, against a generic one and couldn't tell the difference (or it wasn't enough for me to spend $200). I didn't investigate into other USB cables that people rave about.

@truman do you know if the SE version is also a 2-chip version, one for redbook and another for high-res? Also thanks for the tip on the tube rolling, think I will be shopping for 6922 tubes soon. BTW How do you compare the improvement of using iFi USB vs the NOS 6922, if I were to do only one of them, which one would you pick?

Essrand, in response to your question, the SE version does indeed also have 2 dacs. I will add that there is an optimizing feature (for both SE and Non-SE versions) which chooses the better dac for the sampling rate, the better jitter management & the best filter choice - very nice. 
The 6922 type tube* change made a bigger difference vs ifi USB 3.0 to me, but be sure to unplug unit well before, not just place in standby mode, and inquire from distributor as to how best to access.

*See: Joe's Tube Lore
for counsel about best 6922 tube choices.

My experience has been (with less expensive DACs than you are using) there is a clear difference in the sound of different USB cables. But also that low cost is not a guarantee of weak sonic performance - some $10-$12 cables sound much better than some $4 or $14 cables - and you won't know what you are getting until you try a few.  Perhaps the generic cable you are using is by luck actually quite good and rivals the pricier AQ job. The greatest success I have had in the bargain rack is with Belkin or HP branded cables with gold plated connectors.

For my reference cable I am currently using a 1.5m solid silver USB cable from Pangea that both I and my hugely skeptical friend have determined sounds better in our systems than what is readily available from the computer shop rack.  I think it is about $80 online at AudioAdvisor. My friend who is an engineer was so annoyed that the cable provided a noticeable sonic difference in AB listening tests that he assumed his generic cable was "broken" and attempted to come up with an empirical test to show himself why the Pangea sounded better.  I think he failed to show any difference in frequency response except with one of the cheap cables tested, even though both the bass and high end sounded significantly clearer with the Pangea. He bought one of the Pangea cables anyway and is listening to better sounding music in spite of his closely held prejudice that it should not. YMMV.