I have some driver flex on both side and it doesn't effect the sound. But I wonder that can "driver flex" damage the drivers in long time?

Did you tried different usb cables? I want to buy a good quality usb cable for sound quality, but im not sure.

If I'll be sure that balanced output of nfb-10se is worth it and nfb-3+ c.2.2 is not necessary, I'll will make balanced hd600 ! Searching.. Thank you for all, but I wonder that in this price level, are there any good option(combo or seperate dac and amp )? I already have nfb-12.

New vision for me ! balanced hd600 with nfb-10se or unbalanced nfb-3 + c2.2( or m-stage), which is good? (balanced headphones is not suitable for headphone outs of normal amplifiers,so retermination process is not first choice for me and of course my iems have not balanced jacks.)

I thought to buy matrix cube dac and m-stage amp for my hd600 until today. Nfb-10Se's price is lower than cube plus m-stage. Is there anybody to compare these devices for me? My hd600 with cardas cables(non-balanced) and I have alessandro ms1i. I will not buy any headphones with balanced option...