Schmalle

No, the opposite: a low impedance of the Helix is driving a high impedance input of the amp.

According to ADAM audio these speakers deliver a max SPL >110dB @1m per pair - that's fairly loud. My ADAM A5x pair is pretty loud, too.

The Helix is able to deliver about +19dBu in line level mode before distorting the DA converters. If you have a preset that puts out -15dBFS and you crank the volume knob you get +16dBu at the output. I'd guesstimate that the patch is +10dBu with the volume knob at 2 o'clock which is twice the level of +4dBu and might well be the max headroom of the Adams input stage.

This. Audio signal transmission is not about maximizing the transmitted power - which would be impedance matching. It's about maximizing level (high voltage) at the input with high fidelity (low current). This is called high impedance bridging / voltage bridging.

Plug your headphones in the headphones jack.

You are right in that an amplifier that needs to tame the signal it carefully amplified to provide a low signal for FX gear isn't that great of a design. A modern amp like a 5150 III i.e. has a tube preamp, an intermediate OP amp based FX loop/preamp send/headphone buffer stage and a tube power amp to do that. Is there a way to use a multimeter to find out the signal voltage and impedance of different points in the signal chain of an amplifier? - Yes, you need a multimeter, a potentiometer or a collection of resistors and a test signal generator for sine waves (a synth/PC/phone will do the job). Then do this.

Something like this?: 60 Hz hum That's most likely coming from a not lifted ground to P.A. which was powered by another outlet. Push the ground lift switch on your Helix when you send a signal to P.A. or ask the sound guy to lift ground on the mixing console.

The USB cable completes a ground loop that acts as an antenna. The loop: socket 1 - power cable - Helix - USB cable - computer - power cable - socket 2 - socket 1. This has 2 effects: 1) Electromagnetic fields inside this loop will be picked up. So if you minimize the area the loop spans you minimize the noise it can pick up. Laying power cables in parallel next to each other helps, also using the USB ports in the back of the computer are usually better, because the loop now doesn't contain the inside of it where the cpu and other stuff produce electromagnetic noise. 2)The loop can also inject mains hum. That can be minimized by plugging PC and Helix into the same wall outlet using a multi socket. Of course not closing the loop is best which can be done by using an USB isolator, but those aren't cheap. If you use a laptop you can unplug it's power supply and prevent a ground loop that way.

HX Edit 3.01, HX Stomp 3.01 Exported patches miss command center settings.

My personal settings for an ambience reverb that I tend to forget it's until I turn it off: Plate - default values with those changes: Decay 2.6 HiCut 6.5 Mix 20% I listen through studio monitors in moderate levels.

Should work if both amps share the same ground. Plug them into the same power strip / multi plug adapter to make sure.

That's normal since the tip of the cable now touches both button paths. If you pull the cable on the HX Stomp a little until it rests (which is exactly the length of the tip) you can test FS5 function as well.

Mine works fine. You can test the button 2 by pulling out the plug on the Mosky a little until it rests naturally. Now it should do whatever button 1 did before.

After setting Global Settings > MIDI/Tap to MIDI PC Send OFF, did you repower your amp? Otherwise it might have been in PC mode and therefore didn't react to CC messages. Did you set the dip switches on the amp to MIDI channel 1?

Increase the reverbs High Cut. Think of it this way: you mix the dry signal with duller reverbed version of it which makes the sum of both duller, too.