Big can of worms here. Ive been doing 4CM for a while with multiple platforms. Some have issues with my gear and some dont.
For hum and general noise, the single biggest advance Ive had was using an Isolating transformer between the helix and my amp.
Cut the noise down to a point where I could play my Friedman preamp without noise gates. All my noise issues were with ground loops between my gear.
The send/return connections from my helix ran to the iso box, then onto the preamp. (or in your case the input and send of your amp.)
Best $50 you can spend. Its was like someone flipped a switch and turned off the noise.
This is of course assuming you have all your levels correct. I run the big volume knob on the helix at full for unity. And I use it as my master volume when I need to turn down for home playing. Works great.
If you create a blank patch with nothing in it but a send/return block whats the noise like then?
