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Heiserman: H251 Tube Mic, Tape Op Magazine
SM57 Mod: Modifying the Shure SM57 Microphone, Tape Op Magazine
Shure SM57 Mods — AudioTechnology
PAIA Tube Mic Pre Modifications, Tape Op Magazine
How to Do the TapeOp Shure SM57 Mod
Eli Audio: While we're talking about modding microphones, here is one for free!! (EN)
How To Modify Your Shure SM57
Anti SM57 - Gearspace
SM57 to SDC clip
Shure SM57 Mods — AudioTechnology
Oktava Mic Mod: Modifying Your Oktava ML52 Ribbon Mic, Tape Op Magazine
How to Do the TapeOp Shure SM57 Mod