Schmalle

Yes.

Interesting case... The Helix was only connected via USB? Were there monitors or any other device connected that were also connected to the laptop?

The difference between balanced and unbalanced signal transmission is noise susceptibility. If you're not bothered by hum/interference, you're good.

So your issue is a common one: a ground loop that is closed when you plug in USB. If the PC is a laptop unplug the AC-adapter and you're good. Otherwise you probably need a USB isolator /ground loop eliminator.

I think we are as we were - good - hopefully - and I probably read to much into your statement " THE BIG KNOB at MAX for best signal to noise ratio" to the point where I wouldn't mind being called pedantic. So I'm guilty of providing TMI on top of TMI which is THE WORST INFORMATION.

Use the right lineout (which is the right lineout to use in your case). Hopefully my answer is the right one to help you out here.

Does your noise level change significantly when you plug/unplug the USB connection? Would you call that your main problem? Or is that a minor contributor to noise levels?

You also don't really wanna proclamate false things, You state false things to a newbie. I correct those so that the newbie doesn't believe false things. I replied to you, not the OP. If SNR was irrelevant, why did you confuse the guy with it in the first place? Otherwise you did a fine job replying to the OP - I didn't feel obligated to add anything of significance - until SNR was mentioned.

Not really. You get the best SNR right before the DACs start to distort. That depends on the patch levels and is not what you'd really want, because that signal is usually too hot for the input stage of the next device. What you usually want in front of an amp is a signal of the same level that the instrument plugged straight into the amp provides - which (given an empty patch with the impedance set to match the amp's) is done when Outputs = INST and VOLUME maxed / disengaged. This provides good SNR, good headroom and a neutral level.

Fav. power source: wind park Fav. speaker: Jason Sadites

Amps make guitar signals louder from instrument level to the level you get at an amp's speaker out. The cab and IR blocks tame the hot signal again to what a microphone including a mic preamp would pick up from a speaker which is line level.

This HX DSP allocations table is frequently cited when it comes to calculating DSP usage.

1. On modern high gain amps make sure the master volume is low enough to not compress/distort high frequencies. 2. Try a treble boost / eq (tilt or high shelf) in front of old school amps. 3. Try the "preamp + speaker impedance eq" way of doing things as discussed in this TGP-thread.

It does make perfect sense if you consider DSP usage.

No, there is no independent headphones sink. Global Settings -> Phones Monitor gives you two options: Main L/R or Send. This relates to the HX Stomp. Other units may vary.