Sambrox: I followed all instructions (Yes, you're right: hot pick-ups from a GLP)
Michael_dk: Only output led is slightly flashing on green but turns red when strumming louder
drog: It's internal from section 1, no popping/clipping when turned of/on. It makes no difference.
Thanks everyone for your suggestions! In the meantime I have tweaked a lot. In fact so much that I don't know how I now achieved avoiding red clipping. So it's still hard to get really clean volumed sounds in the blink.of an eye.... I've learned too that it sounds much better to NOT choose a distorted amp from the amp section but to stay close to the chosen clean amp and then use the gain knob for a lead solo and store then as your lead rig.
This would mean that if I finally (!) have a really clean and not red clipping rig, I can use this for a lead sound as well, by just increasing the gain.