DDJ-RB and Amplifier

 Hello, 

I just bought a new amplifier with new speakers and I wanted to connect my controller DDJ-RB with the master (RCA) output to my amplifier (RCA too). And I just can't do it, I don't know why, I'm using a MacBook Pro. I have the latest version of RekordBox, actually the problem is that I don't know how to select the speakers in Rekordbox's software. I show you some pictures of my settings. If anyone could help, thanks by advance.

There's also this window about selecting speakers, this window never pops up for me, maybe it would solve the problem if I could find it.

Sorry for my english too