Well... the TubeNOScenti will wax poetic about the differences between tubes in tonality, presentation, the holographic 3D space between instruments, the depth between instruments, sometimes the remarkable depth OF an instrument, as opposed to the flat 2D paper thin presentation of many SS devices. And on occasion, may debase themselves to describe gauche bass that smacks. But only after drinking too much.
Music is in the midrange and tubes excel in delivering an intoxicating mix of vibrant life with warmth and exquisite detail. The fun in tube rolling is discovering all the different flavours - between warm and gooey to clean, incisive and quick. With budget and insanity remaining, combining a wide variety of driver tubes with a smorgasbord of output tubes for the ultimate combolatorations
(it's a word in the secret thermionic code). Sometimes one discovers a magic combo of drivers/output that reveals an encompassing soundstage - on phones - with out-of-the-head width, depth and height that can intoxicate one out of their mind. This week. Next week it's a different gourmet treat on the sonic menu.
Since tubes are more linear within their working range and far more forgiving outside it than solid sand that only measures so stunning just before they clip like a grisly bear getting a buzz cut, tubes preserve the micro-fish of micro-detail that often seems bleached-out, greyed-out by high feedback chip devices.
Other than that, not a big deal.
Except...... the even bigger deal. Tube rolling can make you a better listener. No, really. Listening for inaudible differences between thousand dollar fuses or cables doesn't make one a better listener, only a better nervosa enthusiast.
There are electrical and physical differences between tubes - even of the same family. Audible differences that draw one inside the music. Effortlessly. Tube rolling develops active listening skills without the homework and term papers. IME, SS presents a facts-only, clinical, uninvolving experience. Do not want - can get that at home with my internet dentistry app.
What makes a tube a fav? Depends on the mood, the music and combo. Which is why I have about 100+ tubes in my Top 5 tube list. Crowded, sure. But never boring. Unlike my SS amps, which sound the same same every freakin' day. How tedious.