Very strange problem. Any comments, ideas or jokes appreciated...

OS?

 

Is that Windows OS? I have no experience with MacOS, so I will presume it's Win.
Guessing wildly here, but changing behaviour when unplugging line out could mean that some background software is watching for changes. Does this happen when you start your audio software, or when no software is running, or both? Do you have some icon in your systray?

 

Does the looped sound mean that your system freezes, does it still work but all you can hear is the looped sound or does sound work as expected, it's just that looped plop on top of everything else ?

 

Hey Joe, if it's a laptop then my shot in the dark is to start troubleshooting by muting the computer microphone (check mic using the sound mixer - muting it is not specially intuitive in Win 10).
Good luck!

 

That’s the price you pay for listening to pop music.

 

Hmmm...maybe uninstall/reinstall any drivers that may have been added for the interface?

 

Sorry Joe. Over my pay grade...

 

There might be nothing with a user interface running, but there will still be a device driver and potentially other background processes involved. The three second interval implies to me that there's something that's trying to do something and will continue trying every three seconds until it succeeds.

What happens if you reboot with only one of the two interfaces plugged in?

 

This. Sounds to me like you have an audio output/input loop happening.

 

Not what you wanted to hear but this is precisely why I got a Mac. I got so frustrated trying to make music on a pc. I also had a Keyport at one time. It eventually started to get weird on me so I stopped using it.

 

You bwoke it bwoe.

 

try reading this Joe
Audio or Sound Popping on Windows 10/7/11 [Solved] - Driver Easy

 

That's the awesomeness of Line 6 and their ability to write software for their products.
I love my Variax's but getting the software side of them setup can be a pita at times.

 

I would build a rhythm track around it and keep adding layers. It will become the soundtrack of your life!you could record it on your phone and take it everywhere. Before people even see you they would say”Here comes Joe!”.

 

I would have suggested bus speed on that USB port (also if too many devices are plugged in on that same block) or perhaps the cable being used as the culprit, but if just unhooking two analog-connected speakers and reconnecting does the trick, that seems much more complex.

Maybe clean the contacts on the line out ports? That or perhaps it's a problem with the DAC or whatever circuitry switches output from one to another when something is plugged in. I have to admit, I gave up on my UX2 around Windows 10 as I had similar issues that never got resolved. Mine showed up in recordings and the headphone output too though.

 

Hey Joe Bad check for bad usb port or cable? Try swapping usb ports? Then I would try to re-install drivers after uninstalling the previous drivers, if that doesn't work I would un-install any software associated with the new hardware.

Remove the old software then re-install the new, sounds like a software conflict it's mouthful I know but it already dosen't work so...