Tube sound is not about warmth. It's about correct presentation.

I own a pair of Legacy Audio Focus XD speakers Ijust got in August 2023, they have an internal 750 WPC Icepower amp, you can run them fully internally amped or bi amped. I tried them both ways, first internally amped. Then I hooked up my VAC Renaissance 70/70 amp that is 30 years old. (Fully updated in Feb 2023) When i got the VAC on the top the soundstage was much wider, deeper and layered immediately. Midrange timbre and spatial information was more real. It is still a very good amp.

In my experience both can be stellar or lousy. Obviously it’s the whole system and room.
Given my youthful sixty seven years I recently invited in a few younger women (supervised with feet on the floor) to also listen when changing from a tube intergrated to a SS. We all picked the SS. The youger ears can hear more.
I had been using a tiptop KT 170 AMP. The SS amp has a bit more power.
Certinally this isn’t any sort of proof but what’s in the whole stew adds up to the final result. I wonder if fellow folks here take into account that their gear’s synergy, especially thier speakers coloring thier preferences. Every one tends to tout thier stuff untill they get other equipment. So there’s that too.

There is no "warm" tube sound. Tubes get warm or even hot and some dimwit reviewer probably used the term "warm" or "warmth" and it went from there. If you believe a sound can be warm or cold, you're like Ralph Wiggum when he said, "It tastes like burning."

@mrskeptic (What’s in a name?) To me ElL-34’s in most amps sound warm. Maybe warm means not fast. Other tubes like the KT-150’s are not as warm (at least in my amp).. There’s something in the micro timing or thier musicality (sound rendering). Last but not least tubes are time proven analog. And many love to see ‘em glow.

It's about added distortion. The end.