Stereo guitar/bass cabinet emulation

Working on the enclosure now. Everything fits as planned. For the light pipes i'm going to use a 3mm round acrylic rods mounted into a LED bezels.
On the GUI side: there is one main tab with quick access to the most used functions plus preset handling. All sections have their tabs with all the controls from the html page.

How are you doing the communication between your GUI in the browser and the pedal? MIDI over USB? Or USB Serial?

WebMIDI (fx settings) + WebSerial (console + status report) in the browser, MIDI+Serial over USB for the Teensy.
The GUI on the pic above is a platformio native linux project for LVGL9.1 which then will be run on the ESP32+TFT. ESP will control the Teensy via I2C.
Boards arrived, now let's hope there will be no or minimal need for bodges.
You been doing great process with this! Fantastic work. I hope this solves all your noise, gain, self-oscillating issues also.

Can you tell you how you populated the board? I see you have bare PCB and stencil so I assume you put the soldering paste yourself, you are able to pick and place the SMD components and have reflow oven to do soldering? I've only done simple PCB's myself with simple components mostly prepopulated at PCB factory (few by hand with soldering iron) so those ADC/DAC chips etc. look scary to work with :D
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Thanks! Noise/oscillation issues are almost gone with the AK converters.

I have used the stencil + solder paste and human pick&place.

For placing the components i use either tweezers (larger components) or a vacuum pick up which i designed some years back. Can't imagine working without it now. The pump is activated by a touch sensor in the handle.

I do have a reflow oven, but for this board i went with hot air station.
QFN packages are actually quite easy to work with. Lots of flux, melt, gently press - the chip will position itself and the excess solder on the central pad can be squeezed out (if there is any). Once done, add more flux and clean the edges from any solder balls. Good quality flux is the key.
Uploaded the GUI code to the ESP to see how it looks on the small screen:

I plan to rework the preset system. I'll go with ProgramChange command for the preset change, giving 128 available presets. Data will be stored on the SD card. I thouight about saving them in the external Flash, but Teensy4 does not have a footprint for it. If there is no SD card detected it will fall back to the 8 presets in EEPROM.
Before the ESP starts to talk to Teensy i wanted to see if everything works when put together into the enclosure, check the current consumption.
Teensy + ESP32S + Display (not using any wireless connectivity yet) draws about 217mA from a 9VDC source.
ESP got a 2nd USB-C connector for programming. I was thinking about adding a small 4 way usb hub, as there is still some space available on the pcb, but meh, touch screen interface is only one option from many, not all using USB.
The red VBUS wire should be disconnected. ESP is powered from the onboard 5VDC switching regulator.
The ideal standoff height is 29.5mm. I've used a 29mm one + one M3 washer.