Tube amps have a signature sound

I've been listening to live music as a sound tech/engineer since the late 70's. My experience has paralleled that of the reviewers in Stereophile, The Absolute Sound, FI, and most other "high-end" rags. Tubed equipment just sounds more like live music than SS. Of course there are tubes that impart colorations(microphonics, sugar coating/glaze, tubbiness, British sound, etc.), and tubes that just convey the truth(usually NOS and German or American). That's why so many of us(tube/musical truth lovers) spend so much time "tasting" so many different tubes. I've got a VK-D5 CD player and a pair of Cary SLM-100s. I've lost count of the tubes tested/rejected before settling on six Siemens CCa's(from the 60's) for the BAT, and the TungSol round plate VT-231s(40's), Sylvania 6SN7W tall bottles(40's), and Winged 'C' 6550's(latest iteration) in my Carys. I'm bi-amping with SS for the bottom because it's just easier to get good/fast bass with solid state. I'm using planar speakers for mains, and a subwoofer sytem has to be fast to seamlessly blend with them. You and I will probably have started a major controversy with your question and my response. Don't be confused by all the opinions you'll get in here. Read what the experts have to say(those not swayed by advertising dollars and that are familiar with live music), you'll find that the highest rated equipment is invariably tubed and SS is usually compared to and judged by how close it gets to that standard. BOY- is THAT statement ever inflammatory!!

The most consistent sonic tube signature is not the sluggish droopy ill defined sound of the golden era of "hi fi"!
Instead I am convinced it is a much more pronounced 3D soundstage. That is if you are talking of the currently produced tube amps. The degree of upper end sparkle and controlled bass, is very variable. That is clearly audible however there is in addition a very important psycho-acoutical sound.
It is referred to as a distortion, but you can't pick it out it is sort of invisible, if you will. I think is 2nd order distortion. Again I can not describe it but it is there and most people really like it. I can say what it is not.It is NOT poorly defined, fuzzy, rolled off, sound or anything of the sort. It is a highly desirable harmonic phenomena.
If you want to hear what I think people refer to as tubey, then you might try to find a tube amp from the "golden era of Hi Fi" i.e. the 50s until the mid 60s". That would be the extreme of the misapprehension of what a typical modern tube amp sound. It is by all means coming from a tubed amp you are thinking of what you heard 40+ years ago. And for all of you who think I don't know that current tube amps vary widely from directley heated triodes to push pull to SETs and they all sound different you are incorrect. However if you have the experience of listening to a current tube amp of any stripe and say that the usual perception/recollection of tubey, then surely you jest.
I happen to enjoy that Hi Fi sound when feeling nostolgic, which is only occcasionally. If you really want to hear the old tubey sound IMHO, Don't forget you will probably hear it best with the same era speakers. For some odd reason I find the source doesn't seem to have the impact it does on modern systems, but clearly a "record player" is appropriate.
Most of these amps are integrated but if component the pre will already have a "phono" stage input, MM BTW. The only other choices were a tuner and reel to reel for the truly insane. I attribute my ability using curse to the Reel to Reel we owned. My father would become increasing frustrated until his rather expansive cursing vocabulary spewed forth. I recall it was about a 50 - 50 chance that it would get tangled up, off track or some other other calamity would happen.
Or I could have simply said just go out and listen to a !@#%%^&* highly regarded, modern tube amp and you will hear what a tube amp sounds like..

What experts have to say has nothing to do with one's decision if you really spent the time to listen to live music.
For example, going to concert, listen to how a live piano and violin play.
The human ears are very sensitive and very adaptive at the same time; if one tells the brain that this is closer to live music, that would be closer to live music.
I do not believe any of the so-called "experts", for example, those "tin-ears, but big money marketing people" would give you, or the poor so called "audiophile" honest answer.
They always recommend the big advertising money sponsor's equipment.
TRUST YOUR OWN EARS !!!!!!!!!!!!!!!!!!

If there is a 'signature sound' it is the low levels of odd-ordered harmonic distortion which our ears are evolved/created to detect. Odd-ordered harmonics are how the ear detects loudness. Tubes make far less of this than transistors. Transistors don't make much either, but the hundredths of a percent that they *do* make is a demonstration of how sensitive our ears are to this type of distortion.

By contrast our ears do not care so much about even-ordered harmonics, but a properly set up push-pull tube amp is not going to make a lot of those either. So if the amplifier is set up right, and other important design considerations are met, a tube amplifier will sound more natural to our ears than a transistor amplifier will.

So IMO, the 'signature sound' is music.