>>2922412
update:
i've added three slide switches, very cool stuff

and
i tried to place down the UI
i'd like to make the thing as small as possible
the buttons grid is 9x9cm
the display is 29x14mm

the rotary encoders are way bigger than i thought and I wasn't able to find any better
the big rectangle is 53x47mm

i have some GPIOs left so i may aswell add another row of 3 buttons

since the UI is taking up so much space i think I'll have to place many components in the back
or in the upper part.. what do you think?
the critical things are: the usb trace pairs, the audio signals and some other things.. probably the display signals
so i need to think carefully where to place: the audio jack, the usb port and the sd card slot
if it's feasible i'd like to have all of them at the bottom.. do you think it's feasible?

so my questions are:
how big should i make the pcb? how close to the edge can i place the rotary shits?
would you place another row of buttons?

if i want to add another jack as line out jack.. can i just split the traces coming out of the dac and connect them to a jack, through a 10 ohm series resistor?