SOULNOTE Kato’s Design Philosophy Part 12

SOULNOTE Chief designer Kato continues his essay series with the topic of the most important aspect of SOULNOTE’s design. This is the final installment of the series.

I always design while listening to music

Previously, I have explained that there is a trade-off between static performance, which can be expressed by measurements, and dynamic performance, which is related to the time axis and difficult to express by measurements. We have also explained why the structure of the chassis affects the sound. This is another element of dynamic performance that can only be judged by listening.
So, to what extent should Static performance be improved? My answer to this is as follows.
As long as there are no problems when listening to music, it is OK.
The most extreme example is the residual noise of a phono equalizer. If the residual noise is lower than the scratch noise of a cartridge tracing a vinyl record, we judge that there is no problem, and everything else is done in pursuit of dynamic performance. In other words, in the end, we just listen and judge.
Finally, we also take measurements. This is to detect manufacturing errors when mass-producing at the factory. When we design, we dare not measure. I also have a feeling that I want to improve the catalog specifications as much as possible for sales purposes. That is why I don’t dare to measure in order to prevent any strange bias in my judgment.

NOS would not have been born if I had measured it before listening to it

I, too, thought that an oversampling digital filter was absolutely necessary. 5 years ago, during the development of a DA converter. I was experimenting with different settings, and suddenly the sound was so much better. It wasn’t until later that I looked at the waveform, and that’s when I discovered that the waveform was stair-stepping. It just so happened that I had the wrong setting and oversampling was turned off. If I had seen the waveform first, I would have corrected it immediately and would not have heard the NOS sound. And SOULNOTE would never have done NOS. Thanks to listening to the sound without measuring, NOS was born.

SOULNOTE respects the sound source as much as possible

A sound source is a vinyl record, CD, or file source. SOULNOTE respects them as much as possible. SOULNOTE is committed to respecting the work of art to the fullest, and we aim to bring out the best in each and every one of them without altering them.
In the development of audio equipment, the question is: “How does SOULNOTE create its sound? I don’t make a sound! I answer. This is because we believe that audio equipment should not create sound. That is why all sound sources are inherently wonderful. But only if you can get all the information recorded in the sound source! The reason for this is that

There is no seasoning to restore freshness

Conventional designs that emphasize Static performance will result in a boring sound with no sense of freshness as it is. There is no doubt in my experience. As I wrote before, I have been convinced of this since I was a student. So it is usually necessary to improve that boring sound later by changing components and so on. This is the true nature of sound construction. However, if you prioritize dynamic performance and design while listening to music, there is no need for sound construction. All you need to do is to carefully remove bottlenecks. Then, the balance will be finally adjusted at a high level, and a wonderful sound will be achieved. Imagine a river that has been dammed up in several places. If you continue to remove the weirs little by little, the river will finally open up to its full potential, and the original flow of the river will be restored. This is the only work that SOULNOTE does.
By focusing on static performance, the time axis is ignored, and the sound that has lost its freshness cannot be regained, no matter how much you work on the sound later. You can’t get back the time that you lost. There is no seasoning that can freshen up sushi that has lost its freshness.
Audio equipment should be tableware.
In the culinary analogy, the sound source is the food, and the audio equipment should be the tableware used to enjoy the food. The dishes should not have holes in them or be coated with sugar. I think of sound construction as putting sugar or sauce on the dishes. Such tableware chooses the music and the speakers.

Sound quality adjustment

In the process of product development, I always listen to music while selecting components, circuits, and structures. I have said this many times before. Finally, I would like to explain my approach to sound quality in detail.
Sound quality can be examined for any speaker, as long as it is above a certain level. Also, as long as the sound source is straightforward, I can evaluate any sound source from any era and any genre. However, sound sources whose time axis has been destroyed by digital processing are excluded.
You don’t know the original sound of the sound source, so why should you be able to examine it?” Don’t you think? To that question, I answer with this. No, even the engineer who finished the sound source may not know the true sound of that source. The reason is that SOULNOTE is not used for playback.”
The reason why we do not select sound sources or speakers for sound quality studies is that it is not a balanced approach. Balancing is the usual way to achieve a good sound by matching the sound to the speakers and the sound source.
I do not take a balanced approach. I only remove obstacles that rob the sound of its freshness or add a habit to it. So the evaluation is “Is it there or not? For example, a three-dimensional echo, a sensation that cuts through space and jumps into your heart, a pleasant feeling that makes you want to keep listening to it forever. We judge whether or not these things are present. For example, you can tell just by the feeling of the air just before the music starts. This kind of feeling cannot be created later with audio equipment. It is definitely present in the original sound source. That is the “soul in the sound source” that has never been extracted before.
This is not a skill that is unique to me. Anyone present can judge it. If we are faithful to the time axis, the difference in sound is obvious to everyone’s ears. That is why my development time is very short. Because it is really easy.


All music is a work of art, a legacy of humanity. And even the souls of musicians who are no longer with us are indeed recorded in their masters. If there is no audio device to revive the soul, it will be lost forever. That must be avoided at all costs. To do so, we need to free ourselves from the curse of Fourier.
I am developing a device to revive the soul. And I feel happy to be in an environment where I can do that. But I still have more to do. Of course, I have not forgotten my promise to Mr. Nakazawa.