Thanks, everybody. I really appreciate you spending time on helping me. What an amazing resource! Still, it does not address my issue. Probably because I am bad at describing it.
The whole thing is based on an experience of not getting anywhere near the tones that I was expecting. Specifically, I get tones which are either flat or unpleasant.
I cannot find one single preset which sounds musical and reasonably correct. That is not what I hear from other users. To make sure the issue is with the Helix, I have tested with several guitars, via line and instrument outputs, with studio headsets, with various amps, etc. Still the same issue.
The tones that I get are hard to describe. Any level of gain or distortion sounds rough, not harmonic. It is not a clipping issue - I have checked. I have checked all the equipment by using instead Neural DSP. There, all the presets sound good right away (and I can easily dial them into something great).
I thought the issue was somehow with the huge gain increase which any amp gives me. But maybe that is not the issue.
What I was hoping for was some advice on narrowing the issue down to something practical. Some way of diagnosing. At the moment, my plan is to go to Neural DSP exclusively. It is just such a shame to never get the Helix to work properly.
Any ideas would be welcome.