I can interface with Jamulus using the usb from my Mackie fxpro, but the playback from Jamulus (so I can hear the other players) requires me to press the "phones/cr" button on my Mackie. But then the beautiful stereo mix from my keyboard goes away! I have changed all the stereo/mono settings in jamulus I can think of. How can I get my keyboard to play in stereo through the Mackie?