Hey there,

quick updates on the project:

• after talking to a friend, I decided to use the AK4558EN codec instead of the AK4621EF because I already worked with it, I already made support code for it for the Teensy, it has single ended inputs and outputs making the analog interfaces design way easier and cheaper (less opamps = less price), and also it uses an I2C control interface instead of a SPI one, hence reducing the max. theoretical number of devices using the SPI bus in a complete MATT powered system
• I decided to use the ARCHER (M50-32xxx) series of Harwin Connectors for all board-to-board connections; their dual row 1.27mm spacing connectors are perfect for my case, since I have connectors right under the Teensy these take half of the space, giving me a lot of freedom for component placement
• I decided to remove some features from the CORE module, making it more barebones and compact; these features are going to be moved on external modules to let users chose which features they need and which features they don't need

I am almost done with the layout of the CORE module, then I'll move on to the PSU and to the analog IO interfaces, then I'll start ordering some protos.

As soon as I finish a module I'll update GitHub and here accordingly, with 3D renderings of the PCBs as well.