... quite sad, that this Problem is not even considered to be resolved...
I finally build up my rig with the Helix Effect as the control Center. I have two amps: a midi controled Blackstar series one 50 and for smaller venues a Friedman Runt20. If the chanel switch od Runt 20 is connected to ext.Amp of the Helix an unacceptable low frequenzy buzz occurs.
Since a fix is not in sight, I will purchase a Voodoo Lab Control Switcher and change to Midi Control. Anyway so I do not have to adapt all my presets and Snapshot to Midi and Amp switching Action... pphhhh