Shure M267
The road mixer that outlived every rival it was ever measured against, and did it on three 9-volt batteries.
Overview
The M267 is a four-input microphone mixer built for the worst conditions a broadcaster can find: a remote truck, a stadium riser, a hotel ballroom with a hum problem. Shure's own manual calls it a compact, lightweight professional mixer that offers performance and capabilities never before available in a modestly priced professional mixer. It was aimed at broadcasters working both in studio and on remote assignments, plus recording studios and sound reinforcement. It is a problem-solver, not a showpiece, and the way it is equipped fits that.
Start with the inputs. Four balanced inputs each switch between mic and line level, and each has its own gain control and low-frequency roll-off switch. Frequency response is specified at ±2 dB from 30 to 20,000 Hz. Phantom power is switchable at 30 Vdc nominal across all the low-impedance microphone inputs, so condenser mics can be fed without a separate supply box. On a remote, that saves you one more wall wart to lose. The manual notes that the same 30 Vdc simplex power is what Shure's own accessories expect, and the M267 was designed to act as a power source for gear like the SM83 lavalier amplifier. The SM83 will run from "Shure M267 and M268 Mixers or PS1 Power Supply" or virtually any supply offering 5 to 52 Vdc simplex voltage.
The output and monitoring side is where the broadcast background shows. There is a mix bus for stacking units, a VU meter, and a front-panel headphone jack with its own level control. The headphone amplifier/line switch uses gold contacts. The Amplifier position is for high-level monitoring and the Line position is for talkback. A gold-contact tone oscillator switch is fitted for line tests and level checks. Automatic muting prevents the clicks and thumps that otherwise come with every power-up, and the active gain controls are there to lower noise, widen dynamic range, and provide automatic input attenuation.
The protection circuitry is unusually thorough for a mixer of this class. A peak program limiter monitors program levels and the power supply level to head off overload distortion, with an adjustable threshold spanning +8 to +14 dBm and a typical attack time of 3 msec. A separate LED peak indicator is provided for each output, lighting 7 dB below the 5% THD clipping point or at the limiter threshold, with a typical recovery time of 500 msec. Distortion is quoted at under 0.35% THD from 30 to 20,000 Hz at +15 dBm output, and under 0.5% IM distortion up to +16 dBm. Equivalent input noise is given as −129.5 dBV, with equivalent input hum and noise at −127 dBV.
Power is the part owners tend to talk about. The M267 runs from AC at 120/240 Vac ±10%, 50/60 Hz, internally selectable, or from DC at 27 Vdc drawing 30 mA at idle. A built-in battery compartment takes three standard 9-volt alkaline cells and delivers approximately 8 hours of continuous operation. The unit switches silently to battery power if the AC fails. Paired with the automatic muting circuit, that keeps a broadcast on the air.
Physically it is a rack-oriented box: 69 mm high, 309 mm wide, 229 mm deep, 2.95 kg (6 lb, 8 oz). With two RKC169 brackets added it drops into an M67 rack panel, or it can be mounted in the accessory panel A268R. Shure also lists the A268R as a black-finish rack panel specifically for the M267 and M268 series. The unit is UL listed and CSA listed as Certified.
None of this was a clean-sheet design. The M267 carries forward everything that made the M67 the industry standard mixer: transformer-balanced inputs and outputs, mix bus, VU meter, low-cut filters, and low RFI and line-noise susceptibility. The new features go on top. The manual is candid about the improvements over the M67: gold-contact mic/line switches on each XLR input and output, a battery check that doesn't interrupt program, more headphone power, lower distortion and noise, and the front-panel headphone jack. Mix (September 1981, p.14) framed the launch in those terms. It noted that a decade after the M67 and M68 set the standards for compact portable microphone mixers, Shure was introducing two new models with features and improvements intended to make them the new industry standards - the M267 for professional broadcasting, the M268 for public address and paging.
The M268 is the natural companion, and the two were designed to work together. The M268 adds a mix bus for simple mixer interconnection, switchable 30 Vdc simplex power, automatic muting, active gain controls, and electronic power supply regulation. Shure positioned it as an ideal add-on to the M267, matched in performance and styling. The mix bus gives the user nine inputs plus the peak indicator and metered output of the M267, with no loss of inputs on either mixer. An optional A268B battery power supply lets the M268 switch automatically and silently to battery if AC fails.
Shure's advertising in the early 1990s ran a full-page boast that the M267 had outperformed, outclassed, outsold, outdistanced and outlived every mixer that ever hit the road, calling it the most rugged, reliable remote mixer ever made (DB, March 1991, p.76; the same copy ran again in DB, March 1992, p.68). That is marketing copy, not a lab verdict. It does have a decade of road use behind it, and the specifications back up the durability claim on paper. A 1994 DB directory listing (July 1994, p.45) describes the M267 as a microphone mixer with limiter for studio, remote or sound reinforcement use. It repeats the 30 to 20,000 Hz range, 120/240V AC operation, and the four switchable mic or line level balanced inputs with individual gain controls and low-frequency roll-off. The same listing gives dimensions of 1.75 in. high, 14.5 in. wide, 8.25 in. deep and a weight of 5 lbs., with a price of $1,595.00. Those figures don't quite square with the manual's metric dimensions and 2.95 kg (6 lb, 8 oz) net weight, so treat the directory numbers as approximate.
Collectors and working engineers come at the M267 from different directions. The studio crowd values it as a clean, transformer-balanced front end with a limiter that behaves. The remote crowd values the battery operation and the silent failover. The practical notes are the same either way. The battery compartment is the first thing to inspect on any used unit, since alkaline cells left in storage are the classic killer of gear like this. The gold-contact switches are a selling point but also a wear point after decades of use. The RKC169 brackets are frequently missing, which matters if rack mounting is the plan. Prices on the secondary market should be checked against current listings rather than taken from a 1994 directory.
It is not a glamorous piece. It is a black box built to keep working when the truck's generator hiccuped, and by Shure's own account it replaced a model that had already defined the category.
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