I know Sonosax has had to release two versions of some of their recent recorders (maybe also the M2D2?) because of the Zaxcom patent. It's interesting that Stagetec, Sound Devices, Zoom, and Tascam do not. I wonder if the method by which Zaxcom gets 135 dB dynamic range from their preamps is not by using multiple auto-ranging DACs, or at least not implemented the same way as those other ones.