I t seems that the bottom line is, if you run unbalanced to balanced, you will produce a ground loop hum at some point. I have done a lot of research on this little point lately, by necessity unfortunately.... I still have some degree of hum when using 1/4 to xlr, unlesss I use it the way I had it initially set up, ie: 1/4 mono to high Z- DI box, then Low Z-xlr out to speakers.
I tried a mono 1/4 to the DI, then 1/4 out "thru" to xlr. I tried adaptors, (1/4 to xlr female, with a built in matching transformer, coupled to a male-male adaptor), and every other possible scenario, to no avail. I probably have $60-$70 in adaptors. I still have hum... except when using the setup as mentioned above.
So if I want to run to a mixing board, I will try it thru the xlr plug on the speaker designed for daisy chaining the speakers. That should get me sound to the mixer for FOH speakers, or when recording... I think :-)
This has been a real learning experience! I can't understand why Roland made the main outs 1/4 unbalanced instead of xlr balanced?!?!?! I think they did just about everything else right, but hoo boy, this was a major "wrong".