How is the amplifier switched on? I have an audi a3 sline 2007 with a chorus head unit with rear amplified. I am installing an alpine single din headunit and have fabricated a harness from quadlock to iso. Is the amp switched on via can buss as i cannot see a switched output from the chorus wiring diagram other than for the cd changer which i don't have? Basically i have two blue wires that need connecting to firstly the remote amp switch and the second to power the antenna.