Hi all I'm newbie here and also very new to live audio. Please help me out with these situations. I just purchased a set of QSC K10 to use with Phoenix 12 channels mixer with FX (bought 8 yrs ago) for home karaoke. 1. When I plug the music source (karaoke machine) into the stereo input of the mixer, although there is no signal of music from the machine (turned of the machine), there's still a hiss sound produce to the speakers whenever I have the fader control up. The...