The Rupert Neve Designs 517 is a ridiculously versatile 500 Series module, a one-and-done solution for tracking both mics and direct instruments simultaneously. The mic pre's high input headroom will take an absolute beating with level from your highest output mics, providing an open, bold tone that your interface probably can't do by itself. If you're blowing up your A/D converter with hot signals, simply engage the intuitive single-knob opto compressor to tame peaks and gently squish the track into the mix. The direct input at the bottom of the module is totally independent from the mic pre circuit, with 30dB of gain and a handy Variphase circuit. Why does this matter? Say you want to record a bass guitar direct and through an amp at once. The 517 gives you control of each, allowing you to dial in the precise phase alignment between the two signals. It's no exaggeration when we say that every single 500 Series rack should have at least one of these workhorse modules.