Why didn Mackie use Onyx preamps for the Mic/Line Cards?
The Onyx mic preamps were not used for two very simple reasons: physical size and control features. First off, the 6″ x 6″ dimensions of a standard Digital X Bus I/O Option Card cannot accommodate the Onyx mic preamp’s circuitry. The TI/Burr-Brown PGA2500 was the perfect solution for this compact-sized design. A Mic/ Line 8 card would not have even been possible without such a compact component. Secondly, the PGA2500 provides digital control over the preamp level setting, which was required to be able to control the mic preamp’s level from the user interface. The Onyx mic pre would have required a modification to add this functionality, and thus could have presented an even higher cost to develop.
