I came across this issue when I was doing a microphone check with the power cable plugged in and monitors plugged in but not plugged into the computer. But, when I opened my daw, and assigned a channel to a track, I could set the input as MONO, channel 1, and it monitors as stereo. I added a track and assigned Channel 2 to the second track and set that input as mono and both tracks monitor as stereo. Apparently when these devices were made,they were designed only to be used with a daw on a computer and all the fine settings are done on the daw. I actually use garage band and I am able to use it with the firebox.