Talking about "sonic signatures" of amplifiers it is worthwhile to mention (and read about) Bob Carver and Bruno Putzeys.
The Carver Challenge | Stereophile.com
Bob Carver - Wikipedia
"Carver caused a stir in the industry in the mid-1980s when he challenged two high-end audio magazines to give him any audio amplifier at any price, and he’d duplicate its sound in one of his lower cost (and usually much more powerful) designs. Two magazines accepted the challenge."
The Carver Challenge | Stereophile.com
Bob Carver - Wikipedia
"Carver caused a stir in the industry in the mid-1980s when he challenged two high-end audio magazines to give him any audio amplifier at any price, and he’d duplicate its sound in one of his lower cost (and usually much more powerful) designs. Two magazines accepted the challenge."
Bruno Putzeys: Head of the Class (D, That is) | Sound & Vision
6moons audio reviews: Acoustic Imagery Atsah