I have had the same problem. I was able to demo an AX8 plugged XLR straight into the same powered PA speakers I have and it sounded amazing. I got the Helix hoping for the same but its muddy horrible sounding. I tried lowering the Helix input, turning the Pad on, made sure I was on line level eg no phantom power coming from the PA, made sure my PA gain wasn't clipping but nothing but distorted mud. So i switched to coming out of the 1/4 into 1/4 same. I told Helix and they sent me another one and same issues now I just found this post and it doesn't seem that anyone has solved this problem. The reason the AX8 was so incredible was you could get amazing amp sounds direct to the PA so no more lugging amps around. Sounds like everyone is using the 4 cable method with success but no success going direct and Helix didn't have an answer for me. This is a major bummer.