I use a Friedman ASM12 for live use. I find an easy way to get round this is to run two jack to XLR cables from the 1/4 inch outputs to the FOH, you can set the signal to be either line of instrument in the global settings. I can then run one of the XLR outputs to the Friedman and control the stage volume using it's control. I guess if the Headrush doesn't have an independent volume control you could always split the signal on the Helix and control the output of each that way but I've never tried it. It works just as well if you have a Variax too, which kinda makes it a dreamrig ;-)