With its large, mu metal shielded transformers, the Shure M67 Mic Mixer is a great candidate for being made into a four channel preamp. Its main drawback is incredibly low headroom, making recording loud sources nearly impossible. This modification changes the Shure M67 Mic Mixer into a 4 channel preamp with improved headroom, using a few new parts.

Full instructions for the mod are available from RodC’s Post on the Tape Op Messageboard.