I used a 2010 Macbook (the white plastic ones) for mixing for a long time. I play a small online mix, live, on Fridays. I would connect my controller to my laptop via USB and I had the laptops 3.5mm jack set up for audio input. So I would use an RCA to 3.5mm cable to go from my controllers audio out to my laptop, and stream to mixlr.
I recently upgraded to a 2015 Macbook Pro. From what I have read, this laptop can also use the 3.5mm jack for audio input, but only when it registers that the cable is a TRRS tip. I have yet to find an RCA to 3.5mm cable with a TRRS tip, other than those that also have the yellow video RCA cable. Im not sure if that cable would solve my problem or not.
Ive been looking into USB sound cards. It seems as if that would be a good solution, except that my Mac only has two USB ports. One is running the controller, and the other is connected to my external hard drive. Ive considered getting a powered USB hub, but Im cautious about how it would effect serato, the controller, loading songs, ect. through one USB port.
Thoughts, ideas and solutions are greatly appreciated. Thanks in advance.