If you added sounds in the format of .Isu, they're not in the correct format. I'm reading that as an uppercase I followed by "su." but it should be a lowercase L followed by the "su." .lsu
Also, converting the sounds to .lsu isn't really necessary with the Obsidian V4 or Diamond boards, they can both take .wav formatted sounds, but they do have to be in the correct sample rate, etc.
Other than that, I'm confused here. You talked about a Diamond saber and an Obsidian board. To which board are you trying to write sounds? Diamond? Obsidian V3 or V4?
I think the OP thought that the sound board and the Diamond controller are two separate units when they’re in fact, just one.