I don’t know what went into Brandon’s research, but here’s a link to the schematic diagram of the MS1B.
It uses a Texas instruments balanced instrumentation amplifier IC at its core: INA163
Rane hosts schematics on their web site for all of their products.
I have owned several Rane products over the years and their engineering work is always top notch.
They utilize a minimalist aspect to their designs and probably decided on the INA163 because it is low cost, yet has extremely low distortion specs and if one designs the support circuitry correctly, it becomes a wire with gain.
I designed and built a 4 channel 1U mic preamp for my home studio based on the INA163 a few years before Brandon discovered the MS1B and had not heard of the Rane model until Brandon was bragging it up.
I hand matched every differential component (caps, resistors) to the smallest degree of accuracy that my equipment could achieve and that is critical to reducing noise in the design.
All additional support ICs were also Burr Brown components and I used the same level of component matching throughout my design.
I can get > 70 db of gain on a channel with minimal circuitry noise and I can hear dust particles hitting the capsule as well as my heartbeat when using my Rode NT2A near full gain.
Rumor has that Grace also uses the INA163 in some of their designs, although I cannot verify it.