Captivating listeners worldwide with high-quality sound.
The untold story behind the creation of ROHM’s MUS-IC audio devices.

September 25th, 2024

The semiconductor manufacturer ROHM was established in Kyoto in 1954. Initially offering resistors, the company has gone on to develop transistors, diodes, and ICs. Recently, there has been a focus on the utilization of new materials such as SiC and GaN in power semiconductor technology, which is expected to contribute to achieving a decarbonized society by increasing efficiency.
In 1971 ROHM became the first Japanese company to establish a presence in Silicon Valley. Now, with a worldwide network of sales, development, and production bases, we continue to progress as a global company based in Japan.
In the 1990s we established QA (Quality Assurance) centers at seven major locations around the world. Here we will introduce our MUS-IC lineup of audio devices that leverages high sound quality based on a spirit of craftsmanship.

Establishing original sound design technology through the pursuit of high audio quality

ROHM’s history of audio ICs began approximately 50 years ago. From cassette tapes to CDs and high-resolution sound sources, we have continually evolved our products to meet the needs of the times in pursuit of better sound. Today, our wide lineup that includes audio amplifiers for adjusting and amplifying audio signals and D/A converters that convert digital sound data into audio have been adopted in a variety of audio devices.
Initially, we designed products based on electrical characteristics such as distortion and noise that, if looking at the specifications alone, would place our products among the best in the industry. However, semiconductors have continued to become more integrated and sophisticated, and about 10 years ago a customer (an audio equipment manufacturer) pointed out that, all things considered, the sound should be better.
To meet this expectation, a dedicated listening room was set up at the Yokohama Technology Center, where we listened to music extensively until we could discern with our own ears the differences in sound that the customer mentioned. This included the 'lack of extension in the female vocals' and the ‘poor localization instruments.’

Audio Device Development

We subsequently verified the correlation between the excellent sound we heard and the electrical characteristics to establish unique sound quality design technology that provides an optimal balance of both. This culminated in 2018 with the release of ROHM Musical Device ‘MUS-IC’, representing the pinnacle of ROHM audio devices that embody the passionate dedication of ROHM engineers who pushed the limits of both numerical performance and superior sound quality demanded by high fidelity audio equipment. In 2021, we released a DAC chip for flagship models that enables easy sound quality tuning for each audio device. And we continue to develop products that contribute to the creation of the ideal sound.

Audio Device Development

MUS-IC audio devices deliver faithful sound reproduction

A brand name reserved exclusively for ROHM's top-of-the-line audio devices, MUS-IC was developed by combining ROHM’s corporate mission of ‘Quality First’ and contributions to music culture together with a vertically integrated production system and original sound quality design technology.
Mr. Sato, who is actively involved in the development of audio ICs at the forefront of the industry, says that the goal of MUS-IC can be summed up in one phrase: ‘faithful sound reproduction.’

‘I believe that the ultimate purpose of audio equipment is to recreate the emotion that music conveys in a realistic way anytime, anywhere. But this cannot be achieved solely by designing based on electrical characteristics such as distortion and noise. I became aware of this fact after I became involved in audio IC development.
To faithfully reproduce sound, we focused on the natural resonance and sense of presence (like listening in a concert hall), the dynamic range (sense of scale) that properly expresses everything from extremely quiet sounds to large amplitudes, and the sense of silence that conveys the tension before the performance begins, as if you were there. By achieving these goals, we hope to represent the artistic interpretation of music created by the performers as much as possible.’

Yoichi Sato, Group Leader
<Yoichi Sato, Group Leader / Senior Member of Technical Leaders, Audio 2 Group, Standard LSI Product Design Department 2, Product Design, Standard LSI Division, LSI Business Headquarters, ROHM Co., Ltd.>

 

In 2020, MUS-IC's 32bit audio DAC was adopted in the latest SACD/CD player from Japanese audio equipment manufacturer Luxman. We interviewed Mr. Nagatsuma, General Manager of the Development Department at Luxman Corp., on his thoughts of ROHM’s audio IC and the process leading up to its adoption.

‘My first impression of the product was that the sound quality was powerful but straightforward. The highs were prominent and the lows remarkably powerful, creating a natural, balanced sound with no standout features. Afterward, we had them make several modifications as we identified the characteristics of the IC, which allowed us to finish the product in a natural way through mutual compromise.
The discussions went smoothly since Mr. Sato was able to engage us on the same level as an audio equipment manufacturer by avoiding personal bias and balance objectivity with subjectivity while listening to sounds.'

Masakazu Nagatsuma, Director
<Masakazu Nagatsuma, Director, Research & Development Dept., Luxman Corp.>

 

Adopted in a number of high-end audio equipment both in Japan and abroad, the MUS-IC series has been highly evaluated for its sound quality not only by audio equipment manufacturers, but also end users.

Creating sound quality through a vertically integrated production system

To achieve a high-fidelity design that satisfies customers, it was necessary to cultivate the ability to distinguish differences in sound quality and understand which factors affect sound quality in the product manufacturing process.
The key to this was our vertically integrated production system, in which everything from circuit design to packaging is carried out in-house. Be leveraging this production system while conducting repeated experiments and listening tests during the manufacturing process, we were able to identify 28 parameters that affect sound quality. Sound quality was then evaluated for each parameter in a dedicated listening room, including for transparency, resolution, localization, and bass, allowing us to provide feedback to the circuit design and production stages to achieve the desired sound quality.

Audio Device Development

For example, in the packaging process, the bonding wire structure connecting the IC chips to the lead frames was reviewed and the material changed from copper to gold. This succeeded in achieving a more lustrous tone for stringed instruments, bringing out a richer, more expressive sound.

In fact, our vertically integrated production system is a critical factor not only in product design, but also the manufacturing process. To achieve high sound quality, it was necessary for the production department to understand the sense of sound that cannot be quantified. Mr. Hamazawa, who was involved in the production of MUS-IC, looks back on those days.

‘We received a request to create test chips in various patterns, but it is not easy to change the conditions for mass production. So, my initial impression of Mr. Sato was someone who voiced troublesome concerns.
But after listening to the sounds over and over again, I began to notice subtle differences. His passion became apparent, and I found myself actually enjoying the process, eventually even to the point of taking the initiative to conduct experiments without being asked.’

Yasushi Hamazawa, General Manager
<Yasushi Hamazawa, General Manager, Technology Development, LSI Business Headquarters, ROHM Co., Ltd.>

 

This passion that transcends divisions combined with proprietary expertise in high quality design are shared among all development members of the audio division as we work to create products.

As long as there is music, we will continue to pursue high-quality sound

We want to contribute to the creation as well as enjoyment of music.
Beginning with ‘A Visual History of Music’ published in 1965 shortly after the company was founded, the ROHM Music Foundation (a public interest incorporated foundation) was established in 1991. We remain committed to the development of music by providing scholarships to more than five hundred students both in Japan and abroad, including Daishin Kashimoto, currently first concertmaster of the Berlin Philharmonic.
At the same time, we offer various other support for the promotion and development of music culture. Especially in Kyoto, where we are working to establish the city as a center for culture and the arts, in 2016 we acquired naming rights for ‘ROHM Theatre Kyoto’ for a period of 50 years. The theatre serves as a base for the creation and dissemination of culture and the arts, and where we actively sponsor music events.
The MUS-IC series was created for music lovers by leveraging the passion and expertise of ROHM engineers.
‘Just as musicians continue to pursue music, there is no end to the pursuit of high-quality sound,’ adds Sato. As long as there is music in the world, the challenge for ROHM continues.

A video is available on ROHM’s website that tells the story of ROHM’s manufacturing including the individuals who are passionate about providing customers with consistently high quality.

Stories of Manufacturing

For everyone who loves music ~The Birth of MUS-IC: Audio Device Development
https://www.rohm.com/company/about/stories-of-manufacturing/mus-ic

Click here for the video.

 

ROHM Musical Device (MUS-IC™) Web Page
https://micro.rohm.com/en/mus-ic/

*MUS-IC™ is a registered trademark of ROHM Co., Ltd.