Here is what I think is a very good discussion about the importance of preamps. In many cases, they can make the single biggest differences of any component. They are not just "pass through" devices. In my experience they are truly interactive in nature and therefore very difficult to get right. They interact with interconnects, media sources, and the RF and other noise sources and do so at various voltage levels. The design of a good preamp is a great combination of science and art. Enjoy what you will...
Check this out- https://www.stereophile.com/content/rotel-michi-p5-preamplifier
Check this out- https://www.stereophile.com/content/rotel-michi-p5-preamplifier