Thanks for pointing out the overabundance of mixers, thats because i never worked with stereo audio signals and since i would like to process and mix in the final output both the oscillators and the processed external audio at the same time i thought a certain amount of stereo mixer channels were required, but i inserted too many.
Okay, but let's say you have something awesome going on and you want to record this to make a track with it. Probably you're going to want to make the final sequencing and build-ups and touches in your DAW anyway, so why not first record your first voice and then your second voice and mix them together when you're making the track in your DAW. For jamming you can put all you sounds through a single stereo out and when it's time to get serious you record the voices separate. Then you only need one stereo pair out and you don't need to constantly use four inputs on your Audio Interface. Makes it also easier to jam with friends on a small mixer. It's up to you of course what you find important and how you spend your cash.
it has individual amplitude controls for every mono channel so maybe that could bring some light imbalance between the Right and Left signal of a stereo sound, does it makes sense to you? Thats another thing im not entirely sure of).
Don't worry about that, you can see it super accurately in your DAW and fix it there :). Maybe it even sounds better with imbalance. I have the Intellijel Triplatt myself and it's great for submixing and fixing/attenuating modulation stuff so I'm sure you will enjoy the Quadratt.
Still i don't understand how a mult could get a double L+R input into one output, i thought they are just replicating the signal inserted in the first patch point: are you saying they can mix 2 signals in a single output like in a mixer?
I just checked it on my eurorack because I confused myself a bit. If I have a 3 mult and I put in 2 oscillators and put the third socket in the Audio Interface then I hear both oscillators. The mult doesn't have real ins and outs. What you put in sockets comes out the other sockets. But here's the thing: in a melody and already enveloped situation I got the sound perfectly. But when I just take the full non-modulated oscillator sounds on the same octave in the mult there's this weird-but-cool noise-cancelation effect going on. So yeah, to be safe submix on the Quadratt and I think most of what you said will be fixed in the module when it outputs both channels to Left (mono). But you can definitely use the mult to put two modulation sources in and use them together at one destination and in a pinch the mult will also work as a equal gain mixer. I have a small eurorack and I like the noisy parts so for me I don't worry and it's 'sound design'.