I'm designing a USB-MIDI board and I decided to go for 4 layers. Since the digital and analog inputs (i.e. potentiometers and momentary push buttons) are distributed throughout the board, it's virtually impossible to separate AGND from VGND. What can I do to minimize noise?
I was thinking about routing the return paths of the digital inputs on one of the signal layers and use the ground plane for analog ground only but I don't know if this is a smart thing to do.
Edit: Thank you for your helpful answers and comments. What I took from that is: It is totally ok to have a single ground plane for analog and digital signals but you should arrange your components wisely and shape that plane in a smart way. Since the layout of the components is mainly determined by the layout of the hardware user interface I cannot do much about that. But of course I can shape that plane.
When I asked that question it was pretty early in the morning and I probably didn't provide enough detail. My PCB has a socket for a Teensy 3.6 which serves as MIDI USB controller and controls a few mosfets as power switches for other attached devices (2x 3 amps). The Teensy has an AGND and a DGND pin. Both grounds are connected inside the Teensy board. I just realized that I indeed could separate AGND from DGND but the shapes of those planes would look a little bit unusual:
It is my first PCB ever (yes I know that's a little bit ambitious for a first project) and I'm not sure if this is a smart approach. Thank you for your help!