Hi,
I've noticed this some time ago, thought it has to be this way, but maybe not...
I have DXR10 hooked to the CABINET output of my Kemper, and when I switch off Kemper and leave DXR10 powered, once Kemper is off, noise (similar to this) comes out of DXR10.
Anyone experienced this (maybe another powered speaker hooked up to CABINET output).
Cheers