“Warm tone” is just another name for gentler distortion, where non-linearities happen before the hard clip limit. It can be modeled pretty well digitally as long as the digital signal itself doesn’t clip, but I agree the real thing is best.
LOL, what? Tubes produce the distortion you hear in most branches of heavy metal, and iconic sounds throughout the whole spectrum of guitar rock.
In its raw form, it sounds awful; it has to be carefully shaped by filters, to remove high frequency "fizz" as well as annoying midrange frequencies to which the ear is sensitive. Even then, that filtered tone isn't something you could listen to via hi-fi equipment or record directly; it is amplified into certain kinds of cabinets with certain kinds of speakers. After all that, some people still hate it. :)
Not really, and it isn't just warmth. The distortion is a unique pattern of simple and monotonically decaying series of harmonics, dominated by moderate levels of second harmonic. This is probably why most find it pleasing.
I think you're talking about very small amounts of it there. As the tube circuit goes into deeper saturation with more gain, it quickly becomes very brittle and displeasing. What keeps the harmonics moderate is low-pass filtering.
I love my tube stereo. It would take an expensive solid-state amp to get close to its character, and it glows like a little fireplace :)
Side note - I have a hunch that the term “warm” was coined unconsciously. It’s not the actual sound; it’s the sound characteristic of warm glowing tubes, the sound of electricity fizzing through hot metal.
For a few hundred bucks, second hand, I can get a distortion-free sound-reinforcement amplifier, that can pump something like 600W per channel into a 4 Ohm load.
The equivalent all tube amp would require a line of credit from the bank, and would need to be on wheels.
To inject pleasing tube distortion into it, which I could turn on and off easily, I could put two inexpensive tube pedals in front of its inputs, like these:
My stereo is 15 watts (through the tubes, but still) - RIP your ears. Agreed that circuits in the preamp stage make the vast majority of the difference.
I like analog hardware mostly because of the knobs, but there is also a nice spiritual connection to the sound energy.
Note that a solid-state amp can still be analog, transistors vs. tubes is distinct from analog vs. digital. Analog solid-state amps can make fantastic sounds, but transistors are much better at staying linear until they clip, so the transitions to nonlinearity/distortion are abrupt and the crunchy tone is less “warm”.
