I have helix lt so it has only one volume knob. My issue was that all amps sounded very weak and i was unsatisfied with any of them. Suddenly i figured out that if i change headphones monitor setting from multi to 1/4 the sound became not only much louder but also fuller. Is this intended behavior? It was not very intuitive to figure out since i always had my volume knob turned up half way and i though that something is wrong either with my gear or the unit. But after changing this setting volume doubled. Thanks