Some free convolution reverb plugins allow you to load "Impulse Responses" (IRs). There are free IR libraries online created by recording the frequency response of expensive microphones. By running your mic through a convolution loader, you can approximate the sound of a high-end mic.
Using advanced DSP (Digital Signal Processing) and impulse response modeling, Mic Mod would take the frequency response, proximity effect, and transient characteristics of your input mic (e.g., a Shure SM57 or Rode NT1) and mathematically morph it into the profile of a vintage Neumann U47, Telefunken ELA M 251, or AKG C12. antares mic mod free download mac