Schmalle

Yes.

Not your fault. I don't know why Line 6 didn't put this information in the manual or the device's labels. A customer service guy named Line6Will stated it here.

No. Both the HX Stomp and HX Effects have impedance balanced TRS Outs. To connect to a balanced input of a console or monitor use a TRS->TRS cable into a TRS/XLR combo input or a TRS->XLR adapter into an XLR input. DI boxes have their place though: they often have a ground lift that comes in handy when dealing with ground loops on stage.

Consider the Boss ME-90.

Not directly. But you can build Astro presets that only differ in the Galaxy setting and switch through those with HX's snapshots.

I'd go with the POD Go and use it's Jazz Chorus preamp sim into the FX return of the JC 85.

Muffled and phasey often comes from mixing either the signal with a short delayed (less than 30 milliseconds) copy of that signal or from mixing a wide stereo signal to mono.

Maybe this helps: Check out the other content on his channel, too.

If Global Settings -> Preferences -> Exp/DS Ring is set to FS5 and Global Settings -> Footswitches -> FS5 Function is set to ToggleExp then this can happen depending on the circuit of the expression pedal that you've connected. It's best to set Global Settings -> Preferences -> Exp/DS Ring to Exp 2 if you don't use FS5.

Consider this thought experiment: You have a high output humbucker guitar A and a low output single coil guitar B. You use guitar A on a clean amp model and level it. Now you switch to guitar B and all the volume is gone. Then you use guitar A on a high gain amp model and level it. Now you switch to guitar B and the volume is still there, it's just less gain / distortion. The point is: uneven default levels will always be an issue because different guitars exist. That said the models in the Helix are quite well leveled when you skip through them. But you can always change the default amp settings with your user settings; nothing stops you from changing the default level of each model if you want. Also you can save amps that you like as Favorites: you can build a short list of amps with settings that you like and skip through them quickly.

I completely agree with the OP. IMHO the parametric EQ in the Helix work but are implemented kind of toy-ish. And there is the wrong implementation of the Q parameter: In the context of resonators (like parametric EQ) there is the so called bandwidth-definition of Q: Q = f_r / Δf Q (Qualtity factor; how narrow a filter is) is defined as frequency-to-bandwidth ratio at the resonant frequency f_r where Δf is the resonance width or full width at half maximum (FWHM). Line 6 uses Q = ( f_r / Δf )² which is wrong. And it's undocumented so you have to stumble over it when trying to copy eq settings from other devices.

Try two cables from OUTPUT L and R into the two channel inputs; if it works you can blend between them using the Pan parameter in the Output block (last circle shaped symbol in the patch's path).

With a non-fx loop amp you just put the HX before the amp. Make sure Global Settings -> Ins/Outs -> Input / Output levels are set to Inst. Other than that the main rule is: Have fun!

No.

If this occurs on multiple presets and different pairs of headphones open a support ticket.

If I read your post correctly you want to apply the four cable method (4CM). The manual explains how this is done.

It can be the potentiometer, it can also be a loose contact in the pedal. It can also be a defective cable - make sure that's not the case before sending it to repair.

The attached file is empty.

These settings seem correct. For this to work both the Wah and the Volume block need to be Bypass Assigned with FS8 as Switch and Latching as Type in the patch. One block needs to be bypassed while the other is active. Make sure there is no other block Bypass Assigned with FS8 as Switch AND Momentary as Type because that blocks the desired toggling. Do you see a "Exp 1 active!" message when pressing the toe switch? - That message should appear even on an empty patch. If it doesn't then check the cable and the toe switch.

Unfortunately the clip is not available using the link in the OP. To reduce the risk of overdriving HX's input with your synth set Global Settings -> INs/Outs -> Input Level to Line. It makes sense to set all levels to Line while you're at it.

The default answer for 4CM is: Set input, output and send/return levels to INST on the Helix and use the -10dB option on the JVM. Use an empty patch, add the fx loop block, crank the VOLUME knob and test how this setup compares the pure non-4CM amp. Usually this sounds very close with an extra little hiss.

Yes, you can do that. I'd start with connecting the 5150's Send with the Low Input of the JCM (no Helix) and tweak the JCM's controls so that it sounds reasonably close to the 5150. Then add the Helix and have fun!

The Cali Texas Ch II topology is: Drive1 -> Bass, Mids, Treble -> Drive2 -> Master, Presence -> power amp. Notice that the second drive of the Lone Star Ch II (called Gain on the real deal) has a bright cap in parallel to the pot leading to leaner sounds with lower values. Btw: compared to the Normal setting Thick and Thicker lower Treble knob frequency which adds mids. It's a very versatile amp model that can produce tons of high class vintage tones. And it loves drive pedals. Tip: since it gets most of the tone from the preamp: try the preamp model with a real power amp.

If 50 Ohms work fine then 80 Ohms is not the problem.

Replacing the power supply is the fix if it's cable has a loose contact (if you're not an electrician).