I was playing my Kemper through a cab today and thought I'd fire up my computer and run through the monitors instead.
As soon as I turned on the interface, there was some crackling introduced to the Kemper signal. It was connected to the interface via spdif.
I though the crackling would go away after the computer was booted up, but it continued. Strumming caused the entire signal to crackle.
Took a power cycle of the Kemper in order to make it go away.