The core is a Teensy4.0 with stereo DAC and headphone amp (under the top board). 

I told myself not to build anything this way ever again. But since tools like this usually wind up this way anyhow, I figured I'd not try to make it more permanent than my immediate needs dictate. I'll likely add a casing at some point. Probably when I graft a battery and comms onto it.

The interface is primarily an Adafruit OLED display, and the SX8634 touch board I built several months ago.