Schmalle

No - the Stomp and the Helix sound the same. Both are flat response with no inherent sound to it - certainly nothing that one would recognize as dull. You could record dry guitar with both interfaces and compare. Are the levels the same? Is one duller than the other? You could play music using both as USB interfaces and compare. Then you should know whether it's the Stomps input or the output that contributes to dullness. What cable do you use for HX -> Headrush?

I'd try the HX Stomp as interface for Native (replacing the Xsonic): USB IN 5/6 -> Native ->USB OUT 1/2 and listen if that sounds dull as well. Make sure the Input Z in the input block is set to 1MOhm or Auto.

To make sure: navigate to the Global EQ, press ACTION and then the Left Knob to Reset EQ.

Check the Global EQ.

I appreciate the time you put into uploading a clip. The clip made me more convinced that there is no or negligible audible difference between said firmware versions.

You need an FX Loop L block in the path for it to work. Also for unity gain make sure Global Settings -> Ins/Outs -> Input Level, Output Level and Send/Return L are set to Inst. Also crank the VOLUME knob.

Mind sharing some comparison clips to convince a doubting spirit like me?

Just use a Send L block in front of the cab block. This way the signal for the power amp / physical cab is on the Send Out.

Besides the jumpered channels in the HX I'd recommend to try the Divided Duo - use Drive1 as a bright channel gain and Drive2 is a normal channel gain. A trick is to set Drive2 to 0, then choose the amount of gain you want with Drive1 and finally add Drive2 back to add body/fullness - pretty cool. Also the Elmsley has the feel of an already dialed in jumpered amp.

If you get less "digital clipping" with less CH Vol then the amp model is not the problem.

Sort of. But not really. There are multiple ways to jumper amps which changes the input impedance in different ways. Using jumpered inputs on an amp means the guitar signal is split and runs in parallel through parts of the amp. Often that's two preamps and both signals are mixed before the power amp. There are some interactions - negligible or audible - that aren't there when you use two parallel amps.

I don't understand the question really but this might be of use: https://helixhelp.com/release-notes/helix/3.15.0#global-midi-control-of-knobs-1-6-pagepage-and-preset-save

If you set Global Settings->MIDI/Tempo->MIDI Base Ch to 1 (or whatever the Strymon is set to) and Global Settings->MIDI/Tempo->MIDI PC Tx to MIDI or MIDI+USB the HX sends PC messages when you change presets. Use this setting, connect both devices with a MIDI cable and to confirm that the Strymon changes presets with MIDI. When it does reset Global Settings->MIDI/Tempo->MIDI PC Tx to Off and use Command Center to program the MIDI PC stuff you need.

That's no problem. You can even do this with just two footswitches: one cycles through the snapshots 1->2->3->1... and one that bypasses one ore more blocks and/or changes parameters. Distinguish between Bypass Assign and Controller Assign and all becomes easy: Bypass Assign: snapshots control bypass states of blocks by default, but you can disable that per block. And you can additionally control a block's bypass state with MIDI and a footswitch or expression pedal. Controller Assign: snapshots don't control parameters in blocks by default. But they are one of the mutually exclusive options of controlling a parameter besides MIDI, footswitch or expression pedal. You can controller assign up to 64 parameters in a patch.

The question is actually quite simple and the answer is even more simple: no. With external MIDI hardware you combine MIDI PC for the preset and CC#69 for snapshot. There is no HX internal equivalent for that AFAIK.

You can use snapshots for this. Toggle or step through snapshots in Stomp Mode by assigning a snapshot command to a footswitch in Command Center.

There is no unloading presets. You can load presets via MIDI PC messages and switch bypass A, B or A+B via MIDI CC messages. Read the Sunset's manual to find out more. You can of course create a preset on the Sunset where A and B are bypassed and load that preset to turn the Sunset "off".

What I proposed is an alternative way. The manual endorses ToggleEXP but that can lead to sync problems with snapshots. You need to set Global Settings -> Footswitches -> FS8 to FS8 Function (and not ToggleEXP) for this to work. The idea is that one block is on at a time while the other is off - FS8 (toe switch) toggles between them. EXP1 controls the Position of both blocks at all times but it is only heard in the block that is currently enabled/not bypassed.

Yes.

Post the lead preset if you want a diagnosis on why it crackles.

No. You need an extra volume block. And you need to use EXP1 for both the wah and vol block and toggle their bypass states with the toe switch.

If the footswitch has LED indicators (like the Catalyst's LFS2) and is passive (no batteries, no power) it will not work with the Stomp.

Make sure to engage USB MIDI in your Global Settings -> MIDI/Tempo: USB MIDI TxMIDI Clock if needed: MIDI PC Tx

Hi! A dedicated relay switcher will definitely work. I think Peavey uses common V+ instead of common ground. Is the channel getting switched (depending on the channel selected on the amp) when you connect both units with the TRS cable (Helix: External Amp <-> Peavey: Channel / Boost)? - If so you can build a modded TRS cable and get either the channel switching or the boost function Helix-switchable: you cut the tip or ring connection and swap the other two e.g. tip and sleeve.

The Marshall 2525 is weird in that the tone controls are after the fx loop.