If somebody can help to solve my question: I have a Scarlett 2i2 and a mixer Beheringer Xenyx Q502USB. Now I need to record a guitars, a bass and a microphone to the PC and I know that I can connect only one guitar to mixer. What if I connect the guitar and bass to the scarlett and the line outputs to the mixer line-in 2/3. The micro should be connected to the mixer to the xlr channel 1 and then by USB to the Mac. If possible I'll have both guitar and bass recorded in the same track I bealive and the micro in a different track. At the moment I have connected 2 audio monitors Eikon to the Scarlett output in order to listen the guitars.
It seems that the Behringer Xenyx USB mixers mix all tracks into one, so you won't have your microphone and guitars in separate tracks in your recording software (unless you record one track at a time).
There is a workaround (found here): pan one track to hard left and one track to hard right. You will then get microphone in one channel and guitars in the other, which can then be split into two separate tracks after recording should you want to process them separately. Of course that means you will only have mono recording, but that probably won't be an issue.
EDIT A further point - I've just realised that the Q502 actually has up to 5 inputs! You don't need the Scarlett. For smaller mixers with fewer inputs, the first diagram is valid.
Here are crude diagrams of the setups:
1) Using Scarlett
Behringer Microphone -------------------> Input 1------ Bal 100 % L | | |---->USB to computer Scarlett | Guitar----------- | |------------> Input 2------ Bass ----------- Bal 100 % R
2) Using multiple Behringer inputs
Behringer Microphone -------------------> Input 1 ----- Bal 100 % L | | | Guitar -------------------> Input 2------|---->USB to computer Bal 100 % R | | Bass -------------------> Input 3 ----- Bal 100 % R
You are not able to map different channels on your mixer to different channels on your recording software. So the balances are a quick fix to separate the voice recording from the guitars when recording all of them at the same time. You may have to 'split' L and R on your software after the recording.
Note that in all these cases the guitars will be irreversibly 'mixed', but you could record guitar and bass separately.