Kichijoji Audio Laboratory


From the technological point of view, KAL considers that designing an audio amplifier demands scientific behavior. It is necessary to investigate essential technical factors directly affect reproduced sound of an audio amplifier. What should be discovered is not merely a correlation between a design and reproduced sound, but is a causal relationship between them and is the reason why the causal relationship is formed. Needless to say, no one can build an audio technology that supports designing an audio amplifier without employing technologies or engineering based on electromagnetism, electronics and other sciences. However, an unique characteristic of an audio technology inseparably connected to psychology or cognitive science also demands deep insight into technical factors disturbing or promoting human cognitive process of recognizing music. By removing factors disturbing the human cognitive process and getting factors promoting the process as much as possible, the best tool for listening to music can be produced. Therefore, a study is needed as a matter of course, which includes building a hypothesis as to a mechanism by which a technical factor affects the human cognitive process and testing authenticity of the hypothesis by an experiment or simulation, in order to construct an audio technology actually useful for designing an audio amplifier. Then, it is not too much to say that a designing method where the technical target is restricted to optimizing of a playback signal waveform visually recognized with ease, such as a waveform displayed by an oscilloscope, is one of the most indirect methods of making a good amplifier used for music listening. It should be recognized that almost all of physical characteristics of an audio amplifier, which a listener can perceive, are not clearly indicated in the playback signal waveform and each of them has not been treated as a target to be measured yet or is really difficult to measure.

In addition to the technological point, designing an audio amplifier requires a designer to establish a viewpoint regarding reproduced music, because any designer is forced to evaluate whether reproduced sound is right or wrong on the basis of his/her own viewpoint. The viewpoint is corresponded to a designer’s thought on what is an essence of music in relation to human senses, namely what are essential elements of reproduced sound that should be chosen and how order of priority should be given to each of the elements chosen.


Needless to say, the viewpoint has a subjective, sensuous or abstract property and can not be completely expressed by words. However, so to speak, KAL thinks that “the right sound” for music is primarily the one that can convey the pleasure of music well. For instance, “the right sound” is the one creating a feeling that music is swinging, cool, interesting or fun, and is also the one by which ecstasy of music can be felt deeply or a feeling of listening to music with no stress can be gotten. In other words, the sound that can give a listener an urge to tap the beat or to feel like crying is right. In an equivocal expression, the sound that can easily show the artistic quality of music or of a musical performance is right. On the other hand, “the wrong sound” is the one that cannot convey the pleasure of music, such as an uninteresting, not charming or dull sound, and is maybe also the sound that cannot clarify whether or not the performance is good and who is the player. Interestingly, the right sound can also show a listener the acoustic character of the amplifier itself, maybe because every device or circuit composing an amplifier has its own unique spectra in electrical or mechanical vibrations, while music is also made of sound defined by synthesis of frequency spectrum of an instrument or voice. An audio amplifier that can make a listener recognize music deeply can also make the listener recognize its own character easily.

What KAL regards as the secondary importance is that reproduced sound has a tone similar to that of live sound or that a musical tonal balance of live sound can be reproduced. Differences between live sound in concert halls or jazz clubs and audio sound by audio systems seem to tend to present a fixed direction. Generally, in an audio amplifier, it is easy to repress a loss of tonal elements related to clarity or transparency of sound. By contrast, tonal elements related to some expressions such as a strong contrast, richness, shade, darkness, thickness or softness in tone colors are apt to be lost. Perhaps these tonal elements derive from a faint sound with very small sound energy, such as an overtone, hitting sound or rubbing sound, and is easily masked by other sound. In the human cognitive process, they therefore seem to be lost in first by a slight fault included in an amplifier. By restraining them from disappearing, the tonal balance similar to live sound comes to be well reproduced. A well-balanced sound also allows the listener to easily catch an interval of inner parts of an orchestra or a sophisticated chord. With respect to a tone control in an audio system, improving a tonal balance of the audio amplifier as a component of the audio system tends to make it unnecessary to attenuate high-pitched tone below a flat frequency response.

When “to get the pleasant of music” and “to get tone-similarity” compete with each other, KAL chooses a design method based on considering that the former should have priority over the later. For example, a technical method by which clarity or transparency of sound are reduced or the tonal elements tend to be lost are emphasized in order to make a tone of reproduced sound similar to live sound, without considering the former, is not adopted, because such a technical method always results in allowing unacceptable boredom or monotony to steal into reproduced sound. And furthermore, it is not so important to minutely adjust the tonal balance in a certain condition, because the tonal balance totally given at last is changed by various factors such as a tonal balance of recording itself, an acoustic property of a room, a frequency response of a speaker system or tonal balances of other components of an audio system. However, it is obvious that “to get the pleasant of music” and “to get tone-similarity” are not independent mutually but are closely related to each other. The fact that the tone of an audio system comes closer to that of live music by improving the former reveals a strong correlation between them.