I just bought a used Focusrite Scarlett 2i2 from Guitar Center online. The focusrite website says that no drivers are needed for the mac, and don't even have any links for downloads. I have a '15 Macbook Pro running Yosemite and using Garageband. I have the interface selected for the audio input/output. I get a really loud buzzing noise no matter what I do. Doesn't matter if I have an XLR or 1/4" cable in or out, or any of the knobs turned one way or the other. There's always a persistent loud buzzing. I can hear myself very very faintly through the buzzing, but the noise is totally overpowering. I've tried everything I've seen around in other forums. Contacted focusrite, but who knows when they'll get back to me. I need help!