first post here so hopefully i am in the correct place.
for my first project into the audio realm i decided to build an audio mixer, as it is something i needed for my room.
The mixer consists of 4 TOSLINK inputs, being fed into a DAC. The DAC i am building is the one on this project page but changed for the 4 TOSLINKS
This allows me to select only 1 digital input to one analog output which is what i wanted.
I then am going to have 4 3.5mm audio jack inputs, the input from those 4 and the DAC output goes to a summing circuit
Then the summing circuit goes to 4 3.5mm jack outputs
this principle is rather easy to my knowledge. now all the analog inputs are going to have linear pots on them to control the volume, and the outputs will all have the same for output volume control. This is where i am getting stuck.
The DAC has volume control which is controlled using i2c communication from an arduino.
So here is where i need some help, and here are my questions;
1) What size linear pots should i use? i was looking at some dual pot sliders, so i have sliding volume control like on a dj mixer
2) I am going to be running headphones from one of the outputs, my headphones are Beyerdynamic DT770 80ohm's
Will an opamp summing circuit be able to power them directly out? or will i need a headphone amplifier ic? if so do you have any suggestions?
my other 3 outputs will be powering speakers or cheaper headphones.
I hope that i have given enough information to get some help, and i am sorry if the title is misleading or i didn't explain this enough, the audio realm is still extremely new to me and i don't understand it much other then the basics i am using here