When Stephen Bright told me he wanted me to review a new microphone, I was excited. He's a pro audio dealer who always comes up with new, high-quality gear for me to try. But when I asked him what kind of mic it was, he told me it was a mod of the Shure SM57 and SM58. I wasn't so excited once I heard that. Don't get me wrong. I love both mics, and that's why I wasn't so eager about the mods. The stock ones sound fine.

That said, I told him to drop one by and I'd give it a listen. I was amazed. The difference between the mod'ed and stock SM57 was not subtle, yet the mod still retained the overall sound and mojo I like from the stock SM57.

I tried an A/B test on a song I knew would sound well using the mic on both vocals and electric guitar - "Can't Get Enough" by Bad Company. I put both mics 6'' away from the outside of the cone on the speaker in my Fender Blues Junior amp. I played a Stratocaster through a Budda PhatMan tube distortion unit to my Fender - no other effects. When I finished recording the two electric guitar tracks, I recorded two vocal tracks, one with my stock SM57, a second with the mod. For the vocals, I just held the mics at my desk. When I finished, I compared the two recordings.

Both recordings sounded good, but the one with the mod'ed SM57 sounded a notch better - very clear, very present, but warm and honest sounding. Exactly what I would expect from an SM57, but more so. I immediately called up Stephen and ordered a mod of my own. A week or so later, a friend asked me if I ever tried the mic on a snare. Good idea, I said, and set up a snare in my studio for a test. I tried two A/B tests against a stock SM57 - one a straight snare snap, another a series of rim shots. Both came out very good, but the mod'ed version seemed more focused, almost compressed, with a bigger bottom. Since I was there, I tried another test with clean electric guitar though my amp. Again, the mod'ed mic sounded warmer, mellower, bigger.

I've heard of SM57 transformer mods for years. Producer Stuart Sullivan [Tape Op #94] first clued me into it, saying that the old Unidyne models of the Shures had better transformers, but to keep prices down over the years, the company had compromised a bit on transformer quality. When I got that information from Sullivan, my mind thought, "Must find old SM57s," rather than bother to replace the transformers themselves. Frankly, I ain't all that practiced with the soldering iron, so with these AMI mods, I can pay someone to replace the transformers for me.

There are three ways to go with this product. If you're handy with soldering irons and electronics in general, you can order the transformer directly from Oliver Archut's site at <tab-funkenwerk.com> and do the mod yourself by replacing the transformer on the SM57 or SM58 mic you already own. Or you can send in the mic you already own and have the transformer installed by Brad Avenson [Tape Op #76] at <avensonaudio.com>. Or finally, you can go to <m221b.com> and buy a brand new SM58 or SM57 with the AMI transformer preinstalled.

The bottom line? If you like the sound you're getting from snare or your guitar amp from stock SM57s, I wouldn't bother. But if you've been hoping you could find something a little more focused, and a little bigger, without putting your Neumann KM 84 at risk of being bashed in with a drumstick, you might want to give these mods a listen.

Tape Op is a bi-monthly magazine devoted to the art of record making.

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