My hd400 changes volume on its own....i'll be playing along and suddenly the volume will drop, and then another few seconds later it will shoot back up again(without me touching anything). It does this sporadically....for example it might operate perfectly for 5 minutes, then the volume will drop for 10 seconds, then it will kick back up to the original volume....wait another random amount of time and repeat the process.
It does this whether hooked up via usb or not, but when i'm using as audio interface, the sound from the computer(backing track, DAW) also drops volume along with the guitar volume.
Things i've tried:
reinstall driver and firmware,
recalibrated volume pedal