Dr. Kuma Takamura from Susumu
Last Thursday, Dr. Kuma Takamura from Susumu presented an excellent session on Susumu's development on thin film resistors that have performance enhancements that would be of interest to audio hardware developers. Before discussing the technical aspects we were treated to Dr. Kuma's interesting path from a PhD in Behavioral Genetics from Tokyo Metropolitan University in the US to being Susumu's production manager in their US factory to ending up as their Senior Research Scientist living in Minnesota.
After discussing the basic properties of resistive materials we took a deep dive in to comparing thick, foil, and thin film technology, and why thin film parts perform so much better for audio applications. It also turns out that for high frequency (RF) applications thin film resistors also perform much better than thick film due to the skin effect.
A look at NiCr and TaN films, which are the common materials for thin film resistors, was next. Dr. Kuma then went further in to the details of the process Susumu uses and some unique passivization technology that they developed that allows them to laser trim the parts after passivization, leading to even further improvements in the performance and stability of the final parts.
The discussion then turned to how Susumu somewhat accidentally ended up with parts that have better performance for audio, as their primary markets are in industrial and medical areas. This included the development of thin film resistors with gold contacts (instead of tin) to survive the 250° C temperatures found in downhole (deep well drilling) applications.
An interesting issue was for Susumu THD means Third Harmonic Distortion as that test (sometimes also called the A3 test) is standardized for resistor manufacturers. It took them a while to understand that audio professionals mean Total Harmonic Distortion. There was also discussion of the IEC standard used for resistor noise measurement and if that aligned with noise that audio designers would be concerned with.
The discussion ended with an honest and open exchange about how much better the performance of the Susumu audio parts were than the standard parts and where and when that improved performance would translate to measurable system level differences.
