I'm pretty helpless in the area of repair/ alteration, too. I simply took the small guitar Roland to my repair guy, who said he simply changed the way the jack was soldered.

To be clear, I'm talking here about use of the small Roland guitar amp only. I line out of the unit into the PA and use the amplifier volume as a monitor.

Haven't tried to use the CM-30's in stereo yet. I've been using one each in two different back-to-back holiday parties.

Russ