I'd like to build a 4 in, 4 out, 9 V powered audio matrix mixer. Basically it's a mixer where each input has a knob to control the amount sent to each output, effectively forming a routing matrix, like this one.
But that one is a passive mixer, very simple but subject to massive signal loss. My goal is to make something that doesn't dampen the signal - it's ok if the signal is a bit dirty.
So far, my plan is to build something like this and replicate it 4 times. Being rather new to analog electronics, I'd like some advices.
This is based on a op-amp summing amplifier. Here are my (maybe silly) questions:
First, is it as simple as putting 4 of those in parallel, sharing their inputs? Or do I have to add something so one bus won't crosstalk with the others?
If I get it right,
R1/R2controls the gain applied to each signal in the final mix. So if I want to sum the signals,
R1 = R2right ? Is it ok to have R1 > R2 so pushing the volume knob all the way up will boost the signal?
If only the ratio between R1 and R2 matters, how should I choose the values R1 and R2 ? Same question goes for the potentiometer's resistance - how should I choose its value?
I guess there are a lot of things missing here. Any suggestion for a beginner?