My pre (Aesthetix Callisto Eclipse) lacks feedback and is dual balanced (dual volume knobs). Add in tube rolling to tame an overly warm mono block configuration or to add liveliness to a sterile SS amp configuration, it gives me the ability to fine tune whatever configuration I find myself in, and achieve deep bass withVon Schweikert’s (21 hertz) speakers.
I also went down the rabbit hole this year and purchased/experimented with a passive pre (Tortuga) that I had professionally built (I was obsessive with getting things just right in even trying different solders at different places to achieve the most neutral presentation). I added a tube buffer in the chain and loved the result, but in the end found that set up wonderful for near field application only. I craved more cowbell during lively rock/country passages. When I used 1940s NOS tubes and was amazed by the delicate warmth that was offered. (FYI: I will be reluctantly listing the Tortuga shortly if anyone is interested).
For our moderator, may I suggest an RCA selector between source and amp, you are not going to be happy with all the wear and tear on RCA connectors down the road. I had one made for my Tortuga that did the trick, but don’t buy a mass marketed selector, have one made to your needs that is robust enough to handle the amount of switching needed. There are several interconnect builders that should be qualified on AudiogoN. I use my RCA selector between stereo and mono TT in my analog chain.
Happy holidays all, and enjoy the music!