Back in the March/April 2006 edition of Tape Op, I saw an article about modding an SM57. The premise is that the transformer adds a lot of unpleasantness to the sound. The solution? Remove the transformer!
Of course, the transformer is in there for a reason. The two biggest reasons are to balance the output, and provide better voltage/impedance matching. Removing the transformer will then unbalance the output (which could cause noise issues if you’re dealing with a significant cable run), and knock down the voltage output (by 10-20dB, reportedly).
With a small stack of 57s, it seems worth a try. I’ll report back on my progress.
Tape Op - Best recording magazine available.
Gearslutz Forum #1 - Discussion of the mod outcome, plus pics.
Gearslutz Forum #2 - More discussion.