Astatic JT-30 : moosers's user review
The Astatic JT-30 is a dynamic microphone that was specifically created for use with harmonica. They're still making this mic, but I believe it's now put out under the Hohner name and know that Shure has a number of similar microphones as well. It's compact in size for holding it up to your harp as you play, and is useful for both studio and live use. I've only used it in the studio for recording harmonica through an amplifier as well as for recording vocals. I don't know the exact differences between a vintage Astatic JT-30 and those that are made today, but I don't think there's too much of a difference. I also don't really know too much about the JT-30's technical specifications in terms of frequency response or anything like that.
The Astatic JT-30 has become famous for being one of the best blue harmonica microphones around. It's the perfect microphone for getting that gritty sound like that of Paul Butterfield and other blues harpists. The JT-30 is perfect even if you're just looking for a mic to play harmonica into an amp with. I've recorded with this mic through amplifiers with harmonica but mostly just with vocals for getting a super gritty and dirty tone. It's a sound that everyone has heard before and starts with using this kind of microphone through a dirty guitar amp. The newer Shure Bullet microphones will definitely do a similar job, but a studio I used to work at had one of these and it was a lot of fun to mess around with - it is the original after all. There's a lot of information out there on the JT-30 in terms of techniques for using it for blues harp. If you're a harmonica player out there looking to get this kind of sound, it's a cheap enough microphone in both the Astatic JT-30 form and otherwise and definitely worth picking one up to mess with.