I was just inquiring on the sonic difference between an op amp and discrete pre amp design.
OpAmp is made up of transistors packaged in an enclosure. Basically a chip vendor designs an OpAmp for one class of applications. Other vendors might provide the same specification OpAmp but with higher performance. You will find some audiophiles changing OpAmp (generally we don't recommend that) to get better performance or different sound.
So instead of using off-the-shelf OpAmp, highly skilled and EXPERIENCE engineer can build the same function out of discrete transistors. Now this gets interesting and this is where unlimited customization is possible. To have an electronic engineer that understand high-end audio is extremely rare, to get one that also knows how to design at the transistor level is nearly impossible. We are fortunately to have our.
We can't say that one approach is definitely better than the other, it all depends on the performance of that particular design around the opamp or discrete transistors.