I have an SM58 setup. I could never understand why it was fine as a vocal mic, but on the accordion ( always playing through other people's p.a. ) I could never hear it in the monitors or the speakers. Until I read Big Nick's FAQs and all was revealed.
Thanks Big - I'm deeply grateful for that info.
Like the man says, Wifred, stick a pre-amp in there and Bob's your uncle. I was so impressed, in fact, that I took a new ( eighty quid! ) SM58 I had, took a very deep breath and attacked it with a 5" angle grinder, to extract the gizmo from inside the goo ( silicon? ) and made a replica.
If you can wait til Saulieu (not long now) I'll show you in greater detail.
It's worth the effort and you get that nice old fashioned appearance as a bonus.