Schmalle

If it was indeed over-voltage check for defective TVS diodes (shorting). Edit: no TVS diodes - just regular ones. See post below.

Try the Helix Effect Finder.

I think there is a conceptual problem with your intended approach: the bypass state of all modulation and delay blocks are saved in every snapshot. You wouldn't be able to cycle through modulations and delays independently. If that is no problem you could cycle through ALL snapshots with one footswitch. And may be use a second one to go backwards (or reset to snapshot 1).

You've done the factory reset without success - you should open a support ticket.

A bit oversimplified statements to illustrate the essence of equal loudness contour aka Fletcher-Munson curves: If you create a balanced sound at low volume it will sound scooped at higher volume - it gets lost although it's loud. If you create a lean and mellow sound at low volume it will sound balanced at higher volume - it comes alive.

What Marshall power amp? What PA speakers? Do they have tweeters? Does regular music (a full mix) played through it sound great?

You don't. You use Exp1 exclusively. Keep in mind that you only switch between wah and volume when volume is full (toe down).

My mistake. I thought you used a HX Stomp for some reason. Everything except the volume knob stuff still applies to the HXFX.

If you set Global Settings -> Ins/Outs -> Input Level and Output Level to Inst and crank the main Volume knob you get unity gain. This means that you get the same level on both outputs that you feed into the input. Or in other words: both amps should sound like you've plugged into them directly with your guitar (unless one or both amps have a non 1MOhm input impedance). I don't see technical benefits in using the Sends instead in your use case. Phase issues can be of two origins: a flipped phase or a delay on one channel. If you use additional digital pedals these usually add delay due to AD/DA conversion. As for the flipped phase (i.e. due to both speaker pushing their speaker(s) in opposite directions) you can put a Stereo Width block last in the chain and set RPolarity to Invert to test this by ear. Ground loops shouldn't be an issue if you power both amps from the same power outlet. It could become an issue when you connect a third device (i.e. a PC via USB).

Yes, the fine tune bar is -3cent...+3cent. The >< indicators turn on/off at +-2cent and the footswitch LED changes from yellow to green at +-3cent.

You're right, it's 10cent/division. If you calculate the distance between 440Hz and 445Hz you get about 20cent. If you tune a note with Reference at 440Hz and then set to 445Hz it's two divisions off. Science, baby.

For single note stuff an auto swell effect is always a struggle. You need to have a balanced guitar where all the notes are the same level. If the higher notes are lower in level they trigger the swell later. This means need to be pick with different intensity depending where you are on the fretboard. And you need to accurately play one note at a time and have a good dampening technique between the notes - otherwise you accidentally don't trigger the swell. Instead of the Adriatic Swell you can use the Autoswell into the Adriatic Delay which gives you more options to adjust the swell. But honestly I'd use a volume pedal for swelling into single notes - it's way easier - at least for me. Hope that helps.

I'd A/B the" trusted high gain pedal" vs the HX pedals and maybe preamps.

That answer is highly ambiguous. Can you answer my question again? Is it "No, I don't hear hum/buzz when the guitar volume knob is closed." Or is it "Yes, I do hear hum/buzz when the guitar volume knob is closed." Is it "Yes, hum/buzz is what I describe as feedback." Or is it "No, hum/buzz isn't the issue here."

The PAD is before the AD conversion. It cuts about half of the signal (about 6dB) so that the user can use high output guitars without clipping the input. If you want to dampen the input signal further (after the AD conversion) you can insert a gain block in the first position of the chain. And yes, I also would really appreciate an input level control in the input block.

If you close the volume knob on the guitar do you still hear hum/buzz? Is that what you call "feedback"?

No. Older Helix's had problems with noise introduced by phantom power though. How does a guitar sound like that's "not enabled"?

In Europe a Stomp comes with the Line 6 NSA27EU-090300 - a switching power supply without transformer or ferrite bead. There are loads of compatible power supplies on the market if you're not satisfied with the original.

To me this reads like a hardware defect. There have been rare reports of errors / defects that start to occur after some time of "heating up". Like: https://line6.com/support/topic/58488-sound-stops-after-anhour-every-time/ You could go into hardware test mode -> UI Test. Press FS4+5 on startup for this. In UI test don't touch anything and wait for some minutes to see if any switch is triggered on it's own. And you could stop the time until the defect happens after startup of the cold unit and see if that time span is somewhat consistent. But: I doubt that this leads to any clue that you can use to fix this yourself - unless you're an electronics guy. The offical service centers can repair it.

The difference is in the wiring. Without soldering iron you can cut the green cable(s) inside and use a dual mono to stereo 1/4" cable. With a soldering iron you can mod the SP1 to become a L6H in two minutes: Desolder the cables coming from the switch from the output jack 2. Output jack 2 is not needed. Desolder the green cable coming from the pot from the output jack 1 and solder the red cable from the switch there instead. Solder the black cable coming from the switch alongside the black cable. The output jack now looks like this: the two black cables (from the pot and the switch) on the sleeve the red pot cable on the tip the red switch cable on the ring

If you want some hands on experience with Q you can call (323) 634-5667. (See Star Trek: Picard, S02E05 "Fly Me to the Moon") Or try the Filter->Legacy->Q Filter and assign an expression pedal to the Freq parameter.

Yes. Path A and path B are stereo. If you use a hard panned Split Y you split a L/R signal to L/L on path A and R/R on path B. If you mix L/L with R/R (default Mixer setting) you get L+R/L+R, but if you hard pan the Mixer you get L/R.

With default settings Split Y is the same as Split A/B. With a Split Y block when setting its BalnceA to L100 and its BalnceB to R100, you can process the L and R channels independently. With a Split A/B block both path A and B get the same stereo signal with levels chosen with RoutTo. So with your setup use the Split block as Split Y with the hard panned settings mentioned above. This way you give each amp one side of the chorus signal. Make sure to also set A Pan to L100 and B Pan to R100 in the Mixer Block to keep both amps separated in the stereo image.

I wouldn't recommend these either. They work ok, but: What you want is an expression pedal with a linear 10k pot. If it has a logarithmic pot the pedal doesn't work evenly. If it's lower than 10k you don't reach 100%. And if it's bigger than 10k you reach 100% too early. In other words: the expression input reads the resistance - each 100 Ohm step translates 1% step in the HX. I.e. 2500Ohm/100Ohm = 25%. Anything above 10kOhm (10000 Ohm) translates to 100%. It really is as simple as that.

The MVP is an active volume pedal. No chance to use it as expression pedal.