"As Chief Design Engineer of Research and Development at the Lvov Radio & Electronics factory (in the Soviet Union) Lamm had both the resources and large pools of test subjects for conducting hundreds of blind and double-blind listening experiments. From these he accumulated massive amounts of data about what happens when people hear certain sounds, including a complex sound like music. With data in hand he used differential equations to develop scientific models that described mathematically what he calls "the human hearing mechanism." He converted those equations into electro-mechanical models and implemented them in specific circuit topologies.
Lamm tested his circuit designs with hundreds of human listening subjects to demonstrate that, given human physiology, only a few combinations of audio circuitry will work for us as listeners. We cannot change how we perceive sound or music, even in the face of what passes for good specs. "As humans," Lamm observes, "we are created in a certain way. We perceive sound on various levels: conscious as well as subconscious or intuitive. We perceive sound not just with our ears, but with the whole body." From his research he developed a set of theoretical ideals against which he evaluates any amplifier. He called these constructs the Absolute Linearity of a System -- a sort of unified field theory of amplifier design that explains how an amplifier should measure if it is to reproduce sound congruent with the way people naturally perceive it. Without going into detail about the specific measurements Lamm uses, the basic high-level idea is this: as gain is applied the amplifier should preserve the harmonic structure and spectral balance of the musical source signal. Lamm’s evaluation criteria also places specific emphasis on the types and values of feedback utilized in an amplifier."
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