Alesis AM51
A fixed-cardioid Class A FET condenser that sold for $549 and undercut a market full of legends.
Overview
The AM51 came out in the first wave from GT Electronics, the division Alesis set up to market vacuum-tube technology built around the designs of Groove Tubes founder Aspen Pittman. It was announced at the 1998 AES show. The AM Series launched as four microphones, and the AM51 was the entry point: a solid-state large-diaphragm condenser at $549. Mix (November 1998, p.?) covered the announcement alongside the $699 AM52 and the tube-based AM61 and AM62. It noted that all the GT mics shipped with a hard case and shockmount, which mattered when accessories were often nickel-and-dimed.
The AM51 is the fixed-cardioid member of the 50 Series. The AM52 offers cardioid, omni and figure-8 selection. The AM51 gives you one pattern and that's it. Mix (September 1999, p.?) described both 50 Series condensers as Class A FET designs with gold-evaporated mylar diaphragms and a switchable -10dB pad and 80Hz low-frequency roll-off. Those two switches are the only controls. They are also the two most engineers actually reach for when a source is too hot or too boomy.
The diaphragm is the talking point. GT's own advertising copy described a super-thin 3-micron, gold-evaporated mylar diaphragm over an inch in diameter, precisely tensioned by hand. Marketing is marketing, but the spec is real. A diaphragm that thin is built for sensitivity and transient detail, and hand-tensioning addresses the consistency problem that plagues large-diaphragm condensers at this price. Whether every AM51 left the factory perfectly tensioned is something only owners can answer.
The broader AM Series drew attention quickly. EQ (June 1999, p.83) ran the GT mics against B&K 4003s with a Millennia preamp. The reviewer liked the bottom end and balanced highs, noted the mics did well on female vocals without high-end hype, and said that having all the pattern options really opened things up. The AM51 is the one in the family that doesn't give you those options.
For a fixed-cardioid workhorse, that may not matter much. A cardioid-only large-diaphragm condenser is the standard first serious mic in a lot of rooms - vocals, acoustic guitar, drum overheads, the front of a guitar cab. The AM51's -10dB pad and 80Hz roll-off cover the two most common reasons to reach for a switch mid-session, and the Class A FET circuit is the conventional solid-state approach for a clean, low-noise front end. GT built the 60 Series tube mics around a military-spec GT5840M tube for warmth and low self-noise. The AM51 takes the transistorized route instead.
Used-market shoppers should treat the AM51 as a sleeper rather than a trophy. It was the cheapest way into the GT Electronics line, it shares its capsule technology and switching with the AM52, and it carries Alesis/GT branding from the short-lived late-'90s condenser boom. Mix (September 1999) was cataloguing that boom when it counted dozens of new large-diaphragm condensers hitting the market in eighteen months. The AM51 had neither the tube mystique of the AM61 nor the pattern flexibility of the AM52, so it never became the one people name-check. That's why it turns up at reasonable prices. Check that the hard case and shockmount that shipped with it are still in the box before you buy.
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