Rek-O-Kut S-320 Micropoise Tonearm
A broadcast-grade pickup arm that tracked at a gram when most home rigs were still crushing records at five.
Overview
The S-320 is a Rek-O-Kut tonearm - not a turntable. People mix them up, since Rek-O-Kut built both and the model numbers blur together in the used market. This is the Micropoise stereo tone arm, a 12-inch playback arm for 12-inch recordings. Collins Radio shipped it as original equipment on the TT-200 turntables furnished with their 808A-1 broadcast console, paired with General Electric sapphire cartridges. A company building transmitters and network-grade audio consoles picked a tonearm for its turnkey broadcast package, and this was the one.
The headline number is tracking force: one gram or less. Tracking error is specified at less than one degree. Plenty of consumer changers were still tracking at three to five grams back then, so an arm that could hold a groove at a single gram without skating out of it was a real engineering claim, and Rek-O-Kut hung their marketing on it. The Micropoise name came from the arm's Omni-Balance system, Rek-O-Kut's term for a balance scheme that let the arm reach both static and dynamic balance with essentially any cartridge bolted into it. The practical payoff is that you didn't need to match the arm to one specific cartridge weight range. Swap cartridges, rebalance, keep tracking.
The arm is a tubular aluminum body with a die-cast cartridge shell. It takes a four-conductor lead, so it accommodates all 3- and 4-wire stereo cartridges, monophonic carts included. The shell is a plug-in, 4-wire type, so swapping cartridges means unplugging one shell and plugging in another instead of re-soldering headshell leads. The pivot uses chrome steel ball bearings, horizontal and vertical. Rek-O-Kut also specified the arm's resonance in the 9-12 cps range, which keeps the arm/cartridge combination away from the audible warp and rumble frequencies that make woofers pump and styli mistrack. It's a design target, not an accident.
The S-320 is the 12-inch member of a pair. Rek-O-Kut also catalogued the S-260, a 16-inch arm for 16-inch transcriptions, the format broadcasters used for long-form programming. The S-320 was never meant to handle those. The S-320 came with a balance weight; the S-260 was catalogued without one, and a separate balance weight was listed as its own part. Buyers chose based on what was in their record library: 12-inch LPs and 45s, or 16-inch transcriptions. The S-320 handled the former, in studios as well as in homes.
Rek-O-Kut's advertising leaned hard on durability as the brand's defining virtue. High Fidelity (March 1963, p.27) ran Rek-O-Kut's pitch that a Rek-O-Kut turntable "is built to play on and on and on," promising the same rotational accuracy year after year, and noted that hundreds of owners reported needing essentially no maintenance. That copy was written about the turntables, but it's the same company, the same factory, and the same design philosophy that produced the S-320: overbuilt bearings, simple mechanisms, nothing that wears out fast. DB-Magazine (July 1969, p.2) made the broadcast argument explicitly, urging readers to walk through the control rooms of their local stations and count the Rek-O-Kut turntables still running, some of them installed for years, with "minimum maintenance, practically no repair." The S-320 was part of that installed base. Collins didn't put it on their console because it was cheap.
If you're hunting one, know that the S-320 is sometimes confused in listings with the S-340, which Rek-O-Kut described in HiFi-Stereo (October 1963, p.77) as "a modified version of the S-320 professional tonearm" - the arm bundled with the R-34 playback system. They are related but not the same arm, and sellers mix them up constantly. If a listing says S-340 and shows a different counterweight or mounting arrangement, believe the photos over the title. The S-320 also shows up in Collins parts catalogs under part number 099 0241 000, with the S-260 listed as 099 0242 000. That helps if you're trying to identify a loose arm with no documentation, since the part number is sometimes stamped or tagged on original examples pulled from broadcast equipment.
The S-320 is not a plug-and-play arm for a casual setup. It's a 12-inch professional arm with a specific mounting geometry, and it expects a plinth or turntable deck drilled to match it. Rek-O-Kut built it to be serviced, not replaced.
The S-320 is a broadcast-spec component with documented use in Collins equipment, but it's a tonearm rather than a turntable, so it doesn't command the prices that complete Rek-O-Kut turntables do. That makes it one of the more accessible ways to get professional-grade Rek-O-Kut engineering into a system, assuming you have a deck that will take it.
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