I first learned about this in a Juan Atkins interview. I had seen the name but didn't know how it differed from the other Emu 1RU ROMpler type guys like Planet Phat. Thanks to Juan I bought one to see what the Z-Plane filter was about. I am still not 100% sure what the story is with it exactly, but its way more interesting than other morphing, state variable filters. This thing is capable of some amazing evolving pads that nothing else can do. I dock it one point for the horrible interface.