Although there are a million threads on level setting for the Helix, I have found non that directly addresses this issue (somewhat inexplicably).
Here's the problem, then I'll describe my settings. I am using the HX Stomp as a pedalboard (i.e., no amp or cab blocks) in front of my amp. The input signal level coming from the Stomp is way lower (about 25-30 db lower) than the signal level going into the amp when I just plug my guitar straight into the amp.
My HX Stomp settings are all default: Input In-Z is on auto; pad is off; main output is set to 0db. Under global settings, both input and output are set to INSTRUMENT level. With these settings, and all blocks empty—effectively bypassing any Helix processing—it would seem that the Helix should be acting like a stomp box on bypass, and just pass through the signal from the guitar to the amp unchanged.
But something in the Helix is causing the signal level to drop drastically between the guitar and the amp. I could crank up the output of the Stomp, but at +20db it doesn't even have enough gain to make up for the signal drop. I might be able to get there by adding a volume block, but it seem ridiculous to have to max out the gain on the Stomp just to get it back to what the amp considers to be instrument level.
Any thoughts on how to simply have the Stomp act level-wise like a regular stomp box? I have also read opinions that the Helix actually prefers a lower input (hence the addition of the pad feature) which seems bonkers to me given how low the level seems to be.