I remember trying a year or so ago with a GC100 where I didn't use that cable, instead I used a direct mono cable. Fried the GC100, Xantech block undamaged. So there is some kind of subtle voltage difference I'd guess. It's a cheap and simple cable and hooked the GC100 up perfectly to a Xantech block. Wont make that mistake again. Since then I've switched to iTachs/Roomie anyway but iTachs still need those cables for the Xantech blocks (though I'm not going to try it without it to see whether stuff doesn't fry anymore).