I had a lot of hiss/noise and 'background digital noise' on clean rigs, and also had quite a low output level going out via XLRs to stereo Mackie SRM350s. Was even considering going back to my heavy old JVM410. This was on 1.0.8.
I did a factory reset (hold top left soft button when switching from OFF to TUNER) and reset and intialised the flash memory. Then loaded a selection of rigs from the exchange (all Till Schleicher's rigs - thank you Till, they are great).
Noise has now gone, and output level is WAY louder - was wondering why the Mackies sounded so quiet, now I know!
So a reset seems to help even without going back from 1.0.8 to 1.0.4. Not sure it was the flash memory reset, having less rigs in memory, or maybe one of the rigs was corrupted - who knows! But it worked for me