I am now using a Douk Audio H7 and an H8. They are fed by a Denafrips Pontus and they feed a pair of Sonus Faber Lumina II speakers. The sound is fantastic. I no longer need to use EQ on my records or streams, except on poorly recorded tracks that feature very good performances. You may find it hard to believe, but they displaced in my main and secondary systems a PS Audio BHK amp and preamp, and in my secondary system a Schiit Freya S and Schiit Aegir. They really sound that good, transparent, smooth, great tonality and instrument separation, and wonderful dynamics.
They do rely on a good source. The Denafrips Pontus DAC feeding off a Denafrips Iris DDC is an awesome combo, and perhaps they make the difference. I had a PS Audio Directstream DAC and a Burson Conductor 3XR but they don't measure up to the Denafrips Pontus in my system. Perhaps another reason for the exceptional performance is that I bi-wire. Bi-wiring does not always have a positive impact. With the Douk Audio and Sonus Faber speakers it does. Quite noticeably the base tightens, there is greater midrange clarity, and high end extension without brightness. Bi-wiring works equally well when I use my Heco Aurora 1000 speakers.
I did not buy the Douk Audio products expecting much. I've come away really knowing firsthand that price and performance don't necessarily go together. We may know that intellectually, but hearing the Douk Audio units is at first shocking and later immensely satisfying. I'm glad I took the chance, even though taking a chance is hardly a good characterization since I could have returned both units to Amazon at no cost. I urge you to consider both units. You have nothing to lose and everything to gain.
But I'll humor you for educational purposes for you. There are a few OP amps that could be rolled. Some of them are the balanced differential section, others are for buffers and other stuff. Have funnnn. 
