SATRI Time Machine – Stereo Sound Interview

Bakoon International’s SATRI Time Machine – Stereo Sound Magazine. 2017 Spring No. 201.

I sat down with Bakoon International’s Managing Director Soo In Chae and Director of Engineering  Keng Koe Ho after they had just finished testing their new products. Listening to the AMP-51R and DAC-21, I marveled at its elegant sound and design. It left me intrigued about the products’ development process and about Bakoon International’s future steps. Bakoon’s pride for their SATRI Circuit and the future they dreamt laid the foundation to all that I had experienced.

 
Bakoon. The Meeting.
 
Soo In Chae
To tell the truth, I’ve had my fair share of wandering, listening to a lot of different audio products before becoming a Bakoon fan. It was still a time of progress for me to answer ‘What is an audio?’ During that time when I was in college, the Bakoon SCA-7511KR was a great reference for making my own headphone amplifier because of its amazing sound. Returning to Korea after my education in the United States and concentrating more on hi-fi speaker based systems, I ran into the AMP-5513 and right there my wandering ended.

Keng Koe Ho
Bakoon and I were neighbors. When I was working at Sony in 2001, I was transferred to Kumamoto and the Bakoon office turned out to be nearby my house. I went to that office to meet Akira Nagai, the founder of the SATRI Circuit. Talking to him awakened the desire to create. I then bought the SATRI-IC and began to make my own SATRI amplifier. That relationship eventually led me to become Bakoon’s R&D partner.

Soo In Chae
As soon as I was captured by Bakoon’s sound, I became eager to know how this product was made. About 10 years ago, there was almost no information about Bakoon so I had to ask around. I finally met the late Kiichi Nishoji, who was the very first person to introduce Bakoon in Korea. And through Kiichi Nishoji, I met his friend Akira Nagai. Not long after, Akira Nagai came to Korea to upgrade my Bakoon amplifier and it was at that moment when my life changed.

Keng Koe Ho
Akira Nagai is someone who is not afraid to think outside the box. This also applied to the SATRI Circuit. Most amplifiers do not stray too far from the traditional textbook amplifier circuits. But  the SATRI Circuit was a whole new idea compared to those conventional circuits. As an engineer, I tried many experiments using the SATRI Circuit. I contemplated about designing a class A circuit to accent its strengths, and also tried developing a push-pull high powered amplifier.

Soo In Chae
After meeting Akira Nagai, I developed trust and conviction towards Bakoon and the SATRI Circuit. It was then when I decided to halt my pursuit of a PhD in industrial engineering and instead, choose to work in Bakoon with Akira Nagai. That was a big challenge. Now that I think about it, after that decision, it took a lot of effort and there were countless numbers of obstacles involved. Developing Bakoon into something that wouldn’t disappoint everyone’s trust was not an easy task.
 
 
 
Proving Possibilities with the AMP-51R
 
Soo In Chae
It was about 3 years ago, when I first learned about the 4th generation SATRI Circuit in its early development stages. I was determined to develop an amplifier with this new technology. However, I didn’t want to simply develop something with the new circuit. I wanted to do something more remarkable. I truly believed that I could create a winner amplifier that would be everything everyone dreamed about. Something that could fulfill user convenience, expand the possibilities of the SATRI Circuit and something that owned quality design and finish.
 
Keng Koe Ho
At that time, I was developing Bakoon’s new bias circuit, control circuit and digital circuit together with Akira Nagai. Akira Nagai suggested the possibility about joining the AMP-51R project with Soo In Chae, whom I had already heard of; about his active part in the international markets. I especially remember agreeing to work without doubt when I heard his words about developing ‘the best’ amplifier. This product, the AMP-51R is an amplifier that dramatically expands the possibilities of the SATRI Circuit.
 
Soo In Chae
From my experience in attending international shows, I found that although users and participants acknowledge the possibilities of the SATRI Circuit, they still tended to inquire a high-powered amplifier. But maintaining the purity of the circuit came first for us. Figuring out how the create a flagship high-powered amplifier with the SATRI Circuit required both expertise in the SATRI Circuit itself and no compromises in the design and parts selection.
 
Keng Koe Ho
A MPU controlled stepped attenuator was introduced to reduce signal loss in the input stage. The latest all new bias circuit was to be used in the output stage. But at the same time, the dedicated driver circuit was to be developed to drive the output transistors. Also we were to completely renew the user interface with a remote control and a OLED display, and implement the latest software to enable complete control of the amplifier. This was our primary goal. This itself was an ambitious goal but while I was developing, the SATRI Circuit seemed to encourage me. Telling me we could do more.
 
Soo In Chae
Because of that, we were able to complete an elevated level of the AMP-51R. Even the foundation of the exterior design is based on the SATRI Circuit. It has to be simple yet creative and the facade should allow the feeling of an elegant sound. The answer to that was none other than minimalism. But developing a high-powered, yet minimal amplifier was not an easy task. If we used an easier plan, the size would have been many times bigger than this.
 
Keng Koe Ho
The reliability of parts are also important when we reduce the physical size of the amplifier. We were strict to choose from the best components which were mostly used in aviation and aerospace products. The SATRI Circuit requires extreme precision, and the number of transistors that are used cannot be compared to other conventional amplifiers. Without the use of the Surface Mounting Device (SMD), fitting all these numerous precise components  into such a slim case would have been impossible.
 
Soo In Chae
Thanks to this, we could also shorten the signal path to minimize further signal loss. I really have to mention the transformer. While we were developing, we custom-ordered a lot of transformers from Canada’s Plitron. After finalizing the final specification, we custom-ordered a gigantic 625 VA transformer from them using their proprietary technology. Despite being fully packed with numerous big components inside, we created a very slim amplifier and the degree of completion is absolutely amazing.
 
Keng Koe Ho
Looking at this brings me a lot of satisfaction. We completely redesigned the main board five times and that brought upon a meaningful transformation and a new model name from the AMP-51 to the AMP-51R. First of all, we replaced our previous bipolar transistor to the newly released high power MOSFETs from EXICON. Following up, we redesigned the output stage and achieved both the purity of the circuit and the driving power. My favorite part of this product is the bias circuit. The key to the SATRI Circuit output stage is the degree of precision in bias control. I’m proud to say that the AMP-51R’s bias circuit was mastered with a totally new concept in bias circuit design.
 
 
 
Bakoon’s Outlook
 
Soo In Chae
We have at last created something fit to be Bakoon’s flagship product. From the knowledge that we acquired from the past, I hope to develop products that utilizes this new circuit in various ways. I also dream to expand our product line with more affordable amplifiers so that we can share Bakoon’s sound with a wider range of audiences. Furthermore, we plan to focus a bit more on the Korean domestic market too. Hopefully, this will bring us opportunities to introduce our products and possibilities to interact more with audiences.
 
Keng Koe Ho
There are so many products we wish to develop but for now we are thinking about a phono preamplifier. We are mapping out a new circuit that could be groundbreaking in solving the problem of reducing noise. I think we will be able to bring about some good news in the near future. All that is left to do is for us is to go back and forth between Japan and Korea and work hard to develop all this.
 
Soo In Chae
Our goal is to bring Bakoon more recognition worldwide. Akira Nagai often said that Bakoon’s audio is like a time machine, because it lets you go back to concert halls or studios of the past. However, Bakoon International will not only give you the past. We hope to truly travel time and move on into the future.
 

* The original article is translated and editied by Bakoon Internatioal Corp.