Potential input jack problems when switching guitars

a settings reset fixes it. Restoring my settings from a backup reintroduces the issue. I reset the settings again, which fixed it, then I did a normal Quick Setup on the FC-12 I have, and immediately the issue returned.

Seems like the problem lies either in the connection between the 2, or something in the FC-12.

Still working with support. Quite curious what the outcome is now.
 
Well folks, I fixed it.

First, let me say you're all welcome to laugh and I expect it, but also... please be kind. Some of us are naturally this stupid.

After several hours of trying virtually everything I could think of: resetting everything, downgrading to 21.0, unplugging the FC-12 and foot switch, trying the other input jacks, etc, I realized what the problem was.

At some point, I must have accidentally depressed the Ground Lift button on the back of the Axe Fx. Probably while plugging in or unplugging XLR cables in the back. I think that turns on Lift, rather than Ground? For some odd reason, it only caused issues while swapping guitars, and was more prevalent with Tweed guitar cables connected to the guitar input (possibly my Fender tweed cables are not shielded as well?).

I know nothing about ground or loop issues, so this isn't exactly a button I would have pushed on purpose. I seem to recall that the unit is set to Ground when you receive it, unless I'm wrong, and I don't recall changing it, which is why I'm considering it accidental user error.

As soon as I hit that button again, my issues went away. (Not only that, but one of my Les Pauls sounded considerably brighter, which is also odd, but nice, because it sounds good and bright through my tube gear.)

Soooo I guess this is the part where we put my post on r/stupidpeople or something like that, but here we are.

Conclusion: if your Axe FX ever starts to squeal when changing guitars, or when you reset the FC-12 to factory settings, or develops an unnaturally loud hum with low-output pickups, make sure you didn't accidentally push the Ground Lift button.

Thanks all for your help. Sorry for wasting your time with my stupidity.

Edit: also a quick shoutout to Michael from support, who is awesome, took me seriously, and never once treated me like an idiot, even though I clearly am.
 
This is happening again for some reason.

It happens consistently when I unplug my PRS SE Custom 24, with a fender tweed cable. Once it happens, it’s permanent. The Axe FX just starts shrieking.

I think it might be a shielding issue. If I plug in a local brand’s heavily shielded cable and use that instead, it doesn’t happen at all. the only way to trigger the same thing with that cable is to plug it in to the Axe FX and repeatedly touch the other connector to the metal switches on the FC-12 (or drop it on the foot switch and let it hit the switches accidentally).

So I’m guessing that the Fender cable just isn’t shielded well. It’s possible the SE isn’t shielded either; my research suggests they’re not. Maybe the combination doesn’t work for this cable and the Axe FX, for some reason.

Anyway, the mystery remains, and I’m not an engineer of any sort, so it probably always will. But I think this is probably user error, or a poorly made cable.
 
It almost sounds like you have a shielding or grounding issue, almost like something is shorting out. Is the Axe in a rack with anything else? There could be a grounding issue somewhere shorting the cables.

Also what firmware is your FC-12, I remember there being some issue in the past that was patched with an update. Maybe try a different cable to the FC-12 and also see if the issue goes away without the FC-12 plugged in as well.

The input LED’s staying dimed is odd, I personally have never seen that.

Stay with support too! In the event it is internal, Fractal support is famous for helping people out!
 
Werpinater said:
It almost sounds like you have a shielding or grounding issue, almost like something is shorting out. Is the Axe in a rack with anything else? There could be a grounding issue somewhere shorting the cables.

Also what firmware is your FC-12, I remember there being some issue in the past that was patched with an update. Maybe try a different cable to the FC-12 and also see if the issue goes away without the FC-12 plugged in as well.

The input LED’s staying dimed is odd, I personally have never seen that.

Stay with support too! In the event it is internal, Fractal support is famous for helping people out!
Click to expand...
I think you're right that it's a shielding/grounding issue, but I don't think it's the Axe. It happens if the Axe FX isn't plugged into anything, and it happens in my new rack too. It also happens if it's in an independent outlet on a different circuit, and it happens without the FC-12 plugged in too.

I'm almost positive it's the cable with some faulty shielding, or the guitar with some faulty shielding.

FWIW, if I flip the cable around that's the worst for it, so the jack that gave me trouble is now plugged into the Axe FX and the other end is plugged into the guitar, I get fewer issues. It still happens, just less frequently. So I lean towards it being the cable.

It's a really weird issue. If I wait long enough once the input is dimed (a minute or two), it will slowly die down on its own.

Since swapping cables basically fixes it now, I think my problem was two-fold: one was that I had the Ground/Lift button engaged, which made this happen with all my cables, and I can see why! The next problem is the cable itself. So I think I just hit the perfect combo of issues. Wanted to report back for the sake of being thorough, but everything works if I don't use that Tweed cable.

The local brand's cable is heavily shielded and apparently uses Neutrik connectors, which i suspect are of a higher quality than whatever Fender buys and less prone to failure. I suspect I didn't notice this with tube amps because I have a habit of putting my tube amps into standby when I swap guitars.
 
FWIW, been going back and forth with support and they also think this is a shielding issue with the cables at this point.

Who knew a couple cheap Fender cables could cause so many issues. I'm sure Fender makes some good cables, but if you're unlucky enough to get a lemon, hooooo boy, you're in for an embarrassing Fractal Audio forum thread.
 
Look into rack isolation tabs. There's ones that are manufactured, but I just make my own now out of a flanged nylon washer. There's ways to ensure that ground loops don't happen between pieces of rack gear, and that one piece makes the ground for all the gear. Star grounding is another option that a lot of studios and pro rigs use to eliminate ground loops.

This may not be your issue or even help, but I thought I'd just throw it out there as it's helped me with issues in the past.

best of luck

Edit, buy a good guitar cable. LOL
 
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