into a single indistinguishable mass, with an excess of white noise permeating their sung words, acting like a white haze obscuring them. In contrast, through the convertor treated with MusiCoat these same three voices were clearly separated and individually distinguishable (that's Joe's voice, that's John's), and there was far superior intertransient silence and black background amongst their sung words, allowing the words to be heard much more clearly.
What's going on here? The various sonic observations documented above can all be explained by the multiple reflection phenomenon, a lingering echo which sonically manifests itself as a kind of modulation noise in the presence of a music signal. The multiple reflections of dielectric polarization, in a transistor or resistor body, cause an echoing burst of noise that is triggered by each musical transient, so this noise is modulated by the music.
Modulation noise is a well recognized phenomenon in other aspects of audio. For example, analog tape tests out as having a certain signal to noise ratio, which is the ratio of a the strongest signal recordable to the background noise of the tape when no signal is present. But the real signal to noise ratio of analog tape is worse than this, because analog tape emits extra noise in the presence of a signal. This can be clearly heard on solo piano recordings, where the initial burst of musical energy from a piano's percussive attack causes the tape to emit a burst of white noise, and this noise echo can be easily heard immediately following each strong piano attack on an analog tape recording.
The multiple reflections of dielectric polarization are triggered by each change in the music signal, i.e. each musical transient, so each burst of noise from these multiple reflections is a modulated echo version of the music itself. Thus this modulation noise correlates with and tracks the music, and so it is usually heard as an artificial coloration, an alteration in the timbre or textural quality of the music, rather than as a separate burst of noise (however, the male voices of the Fairfield Four's backup chorus exposed this modulation noise more clearly as a separate white noise haze, in the same way that a piano exposes analog tape's modulation noise more than other music does).
Because this burst of dielectric modulation noise seems white, it is biased toward higher frequencies, and thus it makes the timbre and textural quality of the music sound brighter (leaner, thinner, colder) than it actually is. That's why solid state and digital have these recognized artificial colorations.
Because this modulation noise lingers with overhang after a transient attack, due to multiple reflections, it makes the transient sound artificially hard, brittle, etc., turning the natural liquidity of a nylon guitar string into glass, and a gut bass string into plastic. That's why solid state and digital have these artificial colorations.
Because this modulation noise is a foreign noise, and because it fills in what should be the black background of intertransient silence, it actually obscures true musical detail and texture. The lingering modulation noise echo from the multiple reflections especially obscures all the rich musical details that immediately follow a strong musical transient such as a string pluck or strongly percussive piano note. That's why solid state and/or digital systems reveal less true musical information than tube analog systems.
Put all these factors together, and you have a very good explanation of the sonic contrasts observed and discussed above. You also have a very good explanation of the cruel paradox of solid state sound: solid state sounds brighter and more articulate (sharper and harder in transient attack) than tube sound, yet it actually reveals less of music's true information, and also sounds artificially 'hi-fi' rather than musically natural.
One would normally assume that a brighter, more articulate audio component should reveal more musical information, but solid state actually reveals less. The multiple reflection, modulation noise phenomenon explains why. The burst of artificial modulation noise energy on the piano's upper register notes in the Liszt adds extraneous brightness to these notes, changing their timbre from natural wood and felt to the metallic clang of metal on metal; this modulation noise with its added brightness not only changes the timbre to an artificial one, but also obscures the true musical information immediately following the transient attack, of the natural subtle sounds of wood and felt.
We know from independent research that what the ear perceives as added hardness (and what the naive listener misinterprets as more impressive hi-fi transient attack) is usually caused not by faster risetime but rather by slower fall time, by overhanging lingering at the peak after the transient has passed. This overhanging lingering makes 'hi-fi' sound superficially more impressive, since there is more emphasis on the transient. But a truly fast audio component actually sounds more delicate, since it has quick recovery and fall time after a transient, and so spends less time lingering at the peak. This overhanging lingering also obscures subtle textural information that immediately follows a transient, and it also fills in what should be the black of intertransient silence. This artificial filling in of intertransient silence in turn makes it harder for the ear to hear the next major transient as a separate event. This is a key reason why the backup chorus of the Fairfield Four was smeared and congealed together through the solid state convertor, while the convertor treated with MusiCoat separated the voices much more clearly, thanks to much better intertransient silence between the complex vocal sounds of the three singers.
Tubes do not seem to have this modulation noise sonic problem -- and they have a virtually perfect dielectric material (a vacuum) next to their conductive elements, so they do not have the multiple reflection dielectric polarization problem that solid state devices do. MusiCoat, applied to
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