Have had this problem with multiple amps.
When using the Helix to switch channels or what ever the amp has switchable (Real amps). When ever using a TS or TRS cable. regardless of which.
The Amps always get a horrific Buzzing. Consistantly. not sometimes.
Googling lead to no answers - but that obviously some people are experiencing the same thing..
This has NOTHING to do with my power source, as it doesn't matter if I'm plugged in at home, at a gig etc.
The buzzing STOPS when unplugging the EXT AMP output.
I do have an external pedal that came with the Amp for switching the mid boost on and off, however I'd like to think I can use the actual functions of the Helix so I don't have to.
I don't really want to have to buy some stupid humbuster or isolating external box to stop this (as this is what some people have done on other forums) it's $30-100 i shouldn't have to spend.