What exactly is "tube warmth"?

[mr_musica]

This must have been asked before, but I couldn't find any specific threads.
I was checking some videos comparing class D and tube amps. And even the reviewers said that tube amps gave some type of "warmth" to the sound. I know what the word means, but I have trouble putting in context of sound.

So, does anyone know what exactly is the "warmth" that tubes have? is it a boost in some frequencies? is it volume or dynamics related?

I can hear some differences in the amps that are compared in videos, but is there a physics definition of what we describe as "warmth"?

 

[gtirard]

this is going to be fun, following...

 

[lokikallas]

"Pleasant" clipping.

 

[Aussie Player]

For me it is a light but noticeable thickening of the notes that make runs sound more fluid and that thickening best translates into a warming of the note. The harshness that many modern amps bring tends to make the tube amp sound even more pleasant to the ear.

When you play tube amps these days, particularly old ones, younger (than me) bass players in particular, notice the different sound immediately and will come and ask questions. I never got that during the transistor or hybrid decades of my playing. When I started playing, everyone used tube amps so there was no discernible difference between us. These days, there definitely is.

Another point is that tube sounds don't demonstrate that accurately on video as no Utube reference demonstrated what standing next to the speaker cabinet will.

If you keep a permanent search on ebay for Marshall Bass amp as I have had for close to 2 decades, it will astound you that an amplifier company with the largest profile and huge amount of heads produced, hardly ever has a single bass amp for sale. Kinda says something.

 

[Tassieviking]

To me a warm sound is more calming, like waves gently breaking on a sandy beach.
Not warm is the noise we make when the dog comes into the room with half of the guitar neck in its mouth and the rest dragging behind on the strings.
Finger nails on a blackboard is not warm.
I think we can tell when the sine waves are more rounded off like through a tube amp, I don't know if this is produced by the valves or the output transformer.
Solid state amps react faster and can produce nearly complete square or triangular sine waves where tube amps most likely rounds the sharp edges off by the time the signal leaves the output transformer.
That's my completely non- educated opinion, just what I think it might be.
Sorry to anyone who is now scared of their dog.

 

[two fingers]

No. There's no literal definition.

Just like everything else we discuss here, it will differ from person to person.

I MY view, tube "warmth" it more about what is NOT in the tone rather than what is. Tubes (to me) don't "boost" anything. If anything tubes (along with the circuits and speakers they are generally part of in "warmer" sounding rigs) filter a few things.

If I had to be more specific, and try to help you visualize what we're talking about, it would be the opposite of a "smiley face" EQ. More of the low mids, mids, and not-so-sparkly highs are present in the tone. Super sub lows and sizzling highs aren't there.

There is also more inherent distortion in many of the classic tube circuits. I'm not talking about overdrive or "angry" distortion. I'm talking about the kind of distortion used as a parameter to discuss power amps of various kinds. This tends to add (again, in my view/to MY ears) some harmonics to the tone.

(Yeesh, half the terms I'm using could warrant their own threads for clarification.)

Again, these are generalizations. The classic tones many here chase (flip top, SVT, HIWATT, Sunn, various Fender, etc.) involve not just tubes, but the entire circuit, as well as speakers. That's a whole nuther can of worms as well.

And, all that said, I can EQ most solid state amps pretty warm as well.

Foggy enough for you?

Good luck finding a definition that you can live with.

 

[musicman556]

In my completely non-professional (musician-wise, or electrical engineering-wise) when someone describes something as "tubey" or having "tube-warmth) two things come into play, the amplifier itself AND the speaker cabs of the 50-60s. I think part of the "warmth" is a perceived reduction in high frequency content. Taken to the extreme, we often call this "dark" sounding.

I feel like that may have had more to do with the cabs (and microphones) of yesteryear. I was born in 1982. I never heard Jamerson play live, nor any Chuck Berry goodness, etc, firsthand. Everything I have every heard of the "golden oldies" era up to classic rock, etc, was a recording. We have all heard recordings that didn't sound at all like what the room sounded in real-life. I wonder how much of our ideas of "classic" or "vintage" tone is shaped by REECORDINGS that may not have been exactly true to the original performance.

The "thickness" idea I believe is related to very mild tube saturation/drive/overdrive that leads to the "pleasant clipping" @lokikallas mentioned. It's not full-on hard clipping sound that the solid state stuff generally exhibits, rather smooth, additional harmonic content that enriches the information AROUND the note. Some of this makes it easier for our brains to process tones and identify actual notes, etc.

Funny enough, the "most tubey" amp I've ever played is an Aguilar Tone Hammer... and it's Class D without any tubes at all! If you got a dozen bass players together and asked them to describe tube sounds, and then plugged them into a ToneHammer without their knowledge, they'd all go "THAT'S a tube amp!)

 

[Deleted member 389437]

Its verys a lot when it comes to the characteristics of a valve amp to people. For me its not as much as a "warmth" but more of a harmonic thing. Tubes have this way of beefing up your signal and adding or bringing out those rich harmonics. Especially when they are being overdriven. Thats where most of their warmth comes from. Especially in guitar amps. But tubes can also be very Hi-Fi and crisp. Like with the Aguilar DB751 (my daily amp) It has 3 12AX7 tubes in the preamp but it has a complete solid state power-amp with 3 Lateral MOSFETS. It has this really deep crisp tone but it also can get very warm and almost sub sounding. It really just depends on the context.

 

[Steve J]

This must have been asked before, but I couldn't find any specific threads.
I was checking some videos comparing class D and tube amps. And even the reviewers said that tube amps gave some type of "warmth" to the sound. I know what the word means, but I have trouble putting in context of sound.

So, does anyone know what exactly is the "warmth" that tubes have? is it a boost in some frequencies? is it volume or dynamics related?

I can hear some differences in the amps that are compared in videos, but is there a physics definition of what we describe as "warmth"?

Harmonic generation.....That’s all there is to it.

 

[KenD]

Just to further confound the question, not all tubes have the same "tube warmth" character. Triodes, pentodes and tetrodes sound different in different applications. Then, of course, there are pentodes and tetrodes connected as triodes.

Many tube purists swear by triodes, which may be why we see triodes most often in preamp stages.

 

[jking138]

To me tube warmth is subtle clipping and compression, with some high end roll-off.
That being said, some tube amps don't sound warm and some Class D amps sound tube like.
At the end of the day it's marketing jargon to sell amps.

 

[KenD]

Harmonic generation.....That’s all there is to it.

A preponderance of even order harmonics.

 

[MultiScaleMale]

Even order harmonic distortion that sounds pleasant to our ears.

 

[ugly_bassplayer]

dunno but it makes prices go up.

 

[Basslice]

To me tube warmth is subtle clipping and compression, with some high end roll-off.
That being said, some tube amps don't sound warm and some Class D amps sound tube like.
At the end of the day it's marketing jargon to sell amps.

+1 This: I was going to say that for me, a tube amp has warm and fuzzy (not the right adjective - I mean fuzzy like a warm pet) sound. Usually a little background hum no matter what you do. My solid state amps also have ambient noise, but it is a hiss.

But the warmth while playing is a buttery, smooth tone that, as noted above, is probably do to the natural compression you get with tube amplification. Probably natural levels of harmonics there too. I am sure all these things can now be modeled, but I like the real deal. At least in my studio.

 

[BOOG]

This must have been asked before, but I couldn't find any specific threads.
I was checking some videos comparing class D and tube amps. And even the reviewers said that tube amps gave some type of "warmth" to the sound. I know what the word means, but I have trouble putting in context of sound.

So, does anyone know what exactly is the "warmth" that tubes have? is it a boost in some frequencies? is it volume or dynamics related?

I can hear some differences in the amps that are compared in videos, but is there a physics definition of what we describe as "warmth"?

Why?!

There is no need to “nuke” it. Let the ears decide and accept it.

 

[mikeswals]

For one, stop listening to videos and go out and try it for yourself.

 

[burgerdj]

My $0.02: Saturation at the preamp stage that adds a very mild distortion and natural compression.

 

[micguy]

Tube amps, even at lower levels (below clipping) add some low order distortion products to the signal - mostly 2nd and 3rd harmonics. Given that it's not that far spectrally from the original signal, and also because our instruments naturally create a lot of 2nd and 3rd order harmonics, you don't hear it as "distortion", but technically it is.

A Fender tube amp on the clean channel, no matter how "clean" it sounds, isn't strictly speaking very clean - it is creating stuff that you don' t put into it. It sounds "warm" because it is coloring the signal, but in a pleasing way.

 

[Lo-E]

Marketing, internet mythology, people listening with their eyes…

Then, when you get past all of that, which is most of it, really, you have some harmonic distortion that people find pleasing.

In reality, there are tube circuits that are very clean and modern sounding and SS circuits that are warm and fuzzy. Good engineers use good circuit design to get the sound they want out of the devices they use. A big part of “tube warmth” is nothing more than romanticism.