Shure 520D Green Bullet

A dispatcher's microphone that harmonica players stole, then Shure brought back on purpose — twice.

Overview

The 520D weighs 630 grams, measures 62.7 mm across and 82.6 mm long, and fits into a cupped pair of hands like it was machined for the job. It wasn't, originally. The Green Bullet started life as a base-station paging and dispatching microphone, and Shure's own documentation notes it was in great demand in that role until the Model 450 replaced it. What saved the design from the scrap heap was the discovery, made shortly before the Green Bullet was due to disappear from the marketplace, that harmonica players loved what it did to a reeds-and-cupped-hands signal.

That is the whole story of this microphone, and Shure has told it more than once. The 520D is a controlled magnetic, omnidirectional microphone with a frequency response of 100 Hz to 5 kHz — a deliberately narrow, deliberately colored band. Shure's catalog copy is unusually candid about why: the controlled low-end response reduces "bassiness" and delivers the "gritty" sound harmonica players want, and the company's reintroduction announcement went further, describing the response as delivering "the optimum amount of distortion necessary to produce the 'dirty' sound that blues, rock, and country players desire." A modern spec sheet would call that a limitation. Shure called it the product.

The impedance arrangement is where the 520D earns its "D." It's a dual-impedance design, switchable between low and high. The catalog gives the minimum load as 150 ohms in low and 15 kilohms in high, with recommended loads of 1,000 ohms and 100 kilohms respectively. Open-circuit output is 0.22 mV in low impedance and 1.6 mV in high. As supplied, the mic connects to high-impedance or unbalanced low-impedance inputs; getting it onto a balanced low-impedance input takes a simple internal modification, which is the kind of detail that separates a working musician's microphone from a collector's shelf piece. The permanently attached cable is a 20-foot two-conductor shielded run, supplied with no connector.

The physical build is die-cast metal case and grille — a solid, unglamorous chunk of microphone that will survive a decade of bar gigs and a few drops besides. It can be cupped in the hands, mounted on a stand, hung on a boom, or gooseneck-mounted, which is more mounting flexibility than most vocal mics bother to offer. Shure's reintroduction copy emphasized that the microphone had been completely retooled and revitalized to guarantee its original performance and dependability — a claim worth reading as a company acknowledging it was reviving a legacy design rather than launching a new one.

The dating here is worth untangling, because the 520D has a longer and stranger life than the model number suggests. EQ-Magazine (January 1994, p.44) put the original 520's first release at May 1949 with an original cost of $16.50, and described the 520D as a dual-impedance version of that original high-impedance "Controlled Magnetic" mic — still in production at the time of that piece mainly because harmonica players wouldn't let it die. The reintroduction covered by the trade press carried a user net price of $91.75 in one announcement and a suggested list of $80 in another; the discrepancy between net and list pricing is ordinary for the era, but collectors chasing a "correct" figure should note both. By the mid-1980s Shure was running the 520D in print campaigns aimed squarely at players who assumed the company only made vocal mics — Studio-Sound ran the same "So you thought Shure only made vocal mics" layout featuring the 520D under a HARMONICA heading in July 1986 (p.34), September 1986 (p.9), November 1986 (p.17), February 1987 (p.7), and May 1987 (p.9). That's five insertions of the same ad in under a year, which tells you exactly how hard Shure was pushing the harmonica market.

Reception among the people who actually use it is best captured by the players themselves. EQ-Magazine (January 1994, p.44) quoted Chicago blues master Sugar Blue, who said he'd been using a Green Bullet for the last 20 or 25 years and liked it because of what it did to his sound — and Shure's own catalog later leaned on the same endorsement, noting Sugar Blue as the 1984 Grammy winner for Best Traditional Blues Album pictured with the mic. An endorser's line is not a lab measurement, but two decades of continuous use by a working bluesman is a more useful data point than any frequency plot.

What the 520D is not: a clean microphone. The 100 Hz to 5 kHz window and the controlled low end mean it will not flatter a vocal, and anyone expecting modern condenser transparency will be disappointed within thirty seconds. It's a specialized tool with a narrow job description, and Shure built it that way on purpose — twice.