Somehow I've got my ULN2 in a state where it will only accept input from one channel at a time. I have tried with 1/4" and XLR cables. If I plug both cables in to a stereo synthesizer, only input 1 shows any activity. If I unplug the input 1 cable, input 2 starts working. I used to have it working with both simultaneously but obviously I messed something up somewhere along the line. No idea how I managed to do it! Any ideas on how I can revert it to the standard behavior?
I must be misunderstanding something, because I don't know how this is possible. I think you should probably open a support ticket, so that our support folks can get the details of what is going on and help you resolve it...