I own a Helix LT with all updates. Never thought to try the 1/4" out until yesterday. I've been using the XLR/mono exclusively at church and runs great and clean. Cabled to a tube Fender Reverb which of course has ambient hiss but once attached to the Helix the hiss is well overdriven. No controls seem to affect the sound. I've isolated guitar, cables, new presets and no joy. Any help?