Yesterday I painted the front decor of the mixer compartment. I will print in a printing house with lamination and self-adhesive underside.
I assembled the whole system to test the operation of the mixer from a USB hub and a USB OTG port. Soldered two cables - USB3.0 in an angular configuration, and USB OTG.
In general, the synthesizer, in breadboard form, works great, the mixing console works with both the hub and the USB OTG port)))
An unpleasant nuance came to light - when the hub is connected to the USB3.0 port of the tablet, the voltage of 5 volts goes to the 12 volt line, and feeds the power amplifier and everything else from the tablet!
I understood why. The current passes through the MOSFET protection diode of the pulsed DC/DC step-down powering the hub electronics.
It is necessary to put a Schottky diode in the 12 volt power supply circuit of the USB3.0 hub, for decoupling.
Thanks to the tablet and the hub for enduring!