Shure M267 Operation & User’s Manual

amplifier specifically designed for professional applications. The excellent performance, versatility and features of this complete, compact console make it an ideal choice for stu- dio, remote, or sound reinforcement use, and as an add-on mixer for expanding existing facilities. It is also ideally suited for use with audio and video tape recorders to provide multi- ple microphone inputs. Features:
Wide, flat frequency response and extremely low dis- tortion up to +18 dBm output
Extremely low noise and RF susceptibility
Four switchable microphone- or line-level balanced-line inputs with individual gain controls and low-frequency rolloff switches. MUMETAL shielding on input transform- ers
Feedback-type input gain controls for maximum clip- ping levels and dynamic range
Output switchable for line or microphone level
Built-in switchable peak limiter cuts output overload distortion, adapts to power supply voltage
LED indicator shows limiter operation or overload with limiter defeated
Externally adjustable limiter threshold (–4 to +18 dBm)
VU meter calibrated for +4 and +8 dBm with range switch. Illuminated with ac operation
Ac or built-in battery operation. Noiseless automatic switchover to battery in case of ac line failure. Battery test without program interruption
Front-panel headphone level control and monitor jack drives almost any stereo or mono headphones; output can be additional unbalanced line feed to drive a tape recorder or power amplifier
Direct mix bus for stacking units
Automatic muting prevents speaker damage during turn-on and -off
Low distortion, high-stability tone oscillator for line test and level checks
All connections phased. Line output terminals phase- indicated
Compact and lightweight, with rugged, abrasion-resis- tant case
Internally selectable 120 or 240 Vac, 50/60 Hz opera- tion
Underwriters’ Laboratories Listed and Canadian Stan- dards Association listed as Certified SPECIFICATIONS Frequency Response 30 Hz to 20,000 Hz, ±2 dB Voltage Gain (at 1,000 Hz) (Outputs terminated: line 600 
microphone 150 
mix bus 3.3 k
headphone 200 , tip-sleeve and ring- sleeve ) Inp t OUTPUT Input Line Microphone Mix Bus Low-Impedance Microphone (150 Ω) 91 dB 41 dB 24 dB Line 40 dB –9 dB –27 dB Mix Bus 55 dB 5 dB – – Inputs IMPEDANCE Input Designed for Use With Actual (Internal) Input Clipping Level Microphone 19 to 600 Ω 1kΩ –32 dBV to –5 dBV∗ (25 mV to 0.56 V) Line Less than10 kΩ 66 kΩ +20 dBV Mix Bus 3.5 kΩ 3.5 kΩ +7 dBV (2.2 V) ∗Depending on input control setting Shure Brothers Incorporated 222 Hartrey Avenue Evanston IL 60202-3696 U.S.A. Model M267 User Guide 27A8376 (SE) 1999, Shure Brothers Incorporated Printed in U.S.A.

ance microphone input 0.5 –34 dB (20 mV) Mix Bus 3.5 kΩ 3.5 kΩ –8 dBV (400 mV) Head- phones 8 - 2000 Ω 200 Ω recommended 400 Ω to 3 kΩ∗∗ +10 dBV (3.3 V) Line 600Ω 150Ω +18 dBm (6.2 V) ∗∗Depending on level control setting Noise Equivalent Input Hum and Noise: –126 dBV (low im- pedance microphone, 150 Ω - 20-20,000 Hz) into a 600 Ω load at full gain Output Noise: –75 dBV (master control fully counter- clockwise), –53 dBV (master fully clockwise), (input con- trols down, 300-20,000 Hz) Output Hum and Noise: –70 dBV (master control down), –51 dBV (master control up) (input controls down, 20-20,000 Hz) Distortion 0.35% or less THD from 30 to 20,000 Hz at +15 dBm output; 0.5% or less IM distortion up to +15 dBm output level Common Mode Rejection 65 dB minimum with input of –20 dBV at 100 Hz Control Interaction Less than 1 dB with any control combination Overload and Shorting Protection Shorting the outputs, even for prolonged periods, will cause no damage; microphone inputs will not be dam- aged by signals up to 3 volts Lo-Cut Filters 6 dB/octave rolloff at 150 Hz Limiter Threshold: +15 dBm (line output level; adjustable from –4 to +18 dBm) Attack Time: 3 msec typical Recovery Time: 500 msec typical Peak Indicator Lights 6 dB below clipping or at onset of limiter action Headphone Output Clipping Level 3.16V (+10 dBV) into 200 Ω Tone Oscillator 1,000 Hz, 1.5% or less THD Phantom Power 30 Vdc open-circuit, 3.3 kΩ series resistance, input switches in MIC position only Operating Voltage Ac Operation: 120 or 240 volts ±10%, 50/60 Hz, 9.5W, internally switchable
Dc Operation: 27 volts nominal at 15 mA typical no- signal, 18 mA typical at 0 VU (+4 dBm) output with headphone load; 21.5 volts minimum Battery life: approximately 20 hours with alkaline bat- teries at +4 dBm output in continuous use; three 9-volt batteries, type NEDA 1604A (Duracell MN1604 rec- ommended)
Supplied wired for 120 Vac operation (See Service section for 240 Vac operation) Temperature Range Operating: –18o to 57o C (0o to 135o F) Storage: –29o to 71oC (–20o to 160o F) Dimensions See Figure 1 309 mm (12 5/32 in.) 68.8mm (2 23/32 in.) 6.3 mm (1/4 in. ) 229 mm (9 in.) FIGURE 1 Weight Net: 2.3 kg (5 lb 2 oz) Packaged: 3.2 kg (7 lb 2 oz) Certifications Listed by Underwriters’ Laboratories, Inc., and listed by Canadian Standards Association as Certified

WARNING This apparatus must be earthed (grounded)! The M267 power supply is energized when the unit is connected to an ac source; disconnect mains (power) plug from supply when not in use. Inputs The four inputs are professional three-pin female XLR audio connectors located on the rear panel and designated INPUT 1 through INPUT 4. The inputs are balanced (inter- nal transformer, MUMETAL shielded); pins 2 and 3 are “hot”, and pin 1 is “ground”. For microphone operation, the switches labeled LINE/MIC (directly above the input con- nectors) must be in the MIC position; for line level inputs, the switches must be in the LINE position. For impedance, clipping and operating signal levels, refer to the SPECIFI- CATIONS section. Outputs The rear-panel connector labeled OUTPUT is a profes- sional three-pin male XLR audio connector. With the adja- cent LINE/MIC switch in the MIC position, the OUTPUT connector is used to feed a low-impedance microphone line or a low-impedance microphone input. With the LINE/ MIC switch in the LINE position, the OUTPUT connector feeds the line-level input of an amplifier, tape recorder, or another mixer. The OUTPUT connector is a balanced out- put with the LINE/MIC switch in either position; pin 1 is ground, pins 2 and 3 are “hot”, and the connector is in phase with the corresponding pins of the input connectors. The rear-panel binding-post connector designated LINE OUTPUT is in parallel with the OUTPUT connector and can be used as a line-level output feed simultaneously with the OUTPUT connector. The terminals are numbered 2 and 3 and are in phase with the corresponding pins of the input connectors. While the line outputs can be used to drive various impedance lines, the VU meter is calibrated for use with a 600 Ω line. The line output transformer will operate properly with up to 100 mA dc in the line. This feature permits the use of standard “dialed-up” telephone lines with dc across them. (Since a slight distortion increase may occur at high output levels with maximum dc current, operation with the VU RANGE switch at +4 dBm is recommended.) Input Gain Controls The front-panel controls designated 1 through 4 are the in- dividual active gain controls for correspondingly numbered inputs. Note that the input connectors are located on the rear panel directly behind their corresponding gain control. The controls set the preamplifier gain and provide preamplifier output attenuation. As the gain is reduced, the preamplifier input clipping level is increased for that channel. Input control 1 serves an additional function as the level control for the tone oscillator when the INPUT 1/OCS 1 switch is in the OSC 1 position. IMPORTANT: For optimum signal-to-noise ratio, the indi- vidual input controls should be operated at as high a set- ting as possible, consistent with maintaining adequate control range and input clipping level. Master Gain Control The front-panel control designated MASTER is the mas- ter gain control which sets the overall output level of the mixed sources (including signals applied to the MIX BUS input). Limiter The front-panel LIMITER IN/OUT switch turns on a fast- acting, peak-responding limiter circuit that cuts overload distortion during loud program intervals without affecting normal program levels. When the LIMITER switch is IN (operating), the mixer output is limited to approximately +15dBm. Increasing the individual or MASTER gain con- trols will increase the average output and the amount of limiting. The limiter threshold can be reset to any other out- put between –4 and +18 dBm if desired. With the limiter switched OUT and tone oscillator activated, adjust INPUT 1 and MASTER level controls to produce an output 0.5 dB higher than desired. Switch the limiter IN and set the LIM- ITER THRESHOLD ADJUST control (accessible though the bottom of the chassis) for the desired level. The front-panel PEAK LED indicator shows limiter op- eration with the limiter in, and operates when program lev- els approach overload with the limiter out. The indicator is much faster than a meter and will be activated by the short- est transient peak, but it remains on long enough to provide easy recognition. Low-Cut Filters The low-cut filters provide a low-frequency rolloff to the response curve as shown in Figure 2. The filters are acti- vated by the LO-CUT IN/OUT switch above each individual input gain control and can be used individually with each control to reduce wind noise or undesirable low-frequency signals such as from condenser microphones or turntable rumble. 500 1,000 50 100 200 20 0 –10 –20 LOW-CUT FILTER ACTION FIGURE 2

rear-panel MIX BUS phono pin jack. This provision is made primarily to facilitate stacking or “multing” M267s to achieve additional input capacity without losing any inputs. With two M267s, for example, the two mixing buses are di- rectly connected, providing two independent master gain controls and two isolated line amplifiers with eight individu- ally controlled inputs. Since the buses are directly paral- leled, a 6 dB drop in gain will occur; and the master or input controls must be increased to compensate. Noise specifi- cations are not adversely affected by this interconnection. Mix bus interconnection can also be made with other Shure mixers, such as the M268, FP42. etc. VU Meter The VU meter is factory-calibrated for use with a 600 Ω terminated line. The VU RANGE switch on the rear panel selects either a +4 or +8 dBm output at 0 VU meter indica- tion. (This switch changes the meter indication but does not change the actual output level.) Microphone output levels are 50 dB below line output. The +4 range is recom- mended for normal use to provide approximately 14 dB of headroom from operating level to clipping level. The VU meter is illuminated by two No. 86 lamps operat- ing well under their normal ratings for a life expectancy of greater than 10,000 hours. The lamps are only lit during ac operation. Consequently, the illumination serves as a visual alarm if the ac is interrupted and the unit has switched to battery. The VU meter is connected on the primary side of the output transformer to assure protection from any dc level on a telephone line. Headphones The headphone outlet appears at the front-panel jack panel designated PHONES. The two-circuit phone jack will accommodate most stereo or mono headphones. The output level is sufficient to provide high volume for use in noisy environments. Note that the headphone output level is also high enough to use as an auxiliary unbalanced line feed to drive a tape deck or a power amplifier. The tip and ring connections of the headphone plugs are in phase with pin 3 of all input and output connectors, and with the tip of the MIX BUS jack. Tone Oscillator The highly stable, low-distortion tone oscillator provides for line test and level checks. The oscillator is instantly ac- tivated by the front-panel INPUT 1/OSC 1 switch; its level can then be controlled by the INPUT 1 gain control on the front panel. The tone oscillator frequency is 1,000 Hz, and the signal appears on both the line and microphone out- puts, as well as the headphone and mix bus connectors. The oscillator should be switched off (INPUT 1 position) when not in use. Phantom Power The rear-panel PHANTOM OFF/ON switch controls the application of phantom power for condenser microphones, such as the Shure SM81 and SM87A, to all inputs. With the switch on and the rear-panel MIC/LINE switches in the MIC positions, +30 Vdc is applied to pins 2 and 3 of each input connection. Series current-limiting resistance is 3.3 kΩ for each input. When using other condenser micro- phones with the M267, verify that the voltage and resis- tance requirements are compatible. Note that the phantom power cannot normally be ap- plied to the inputs with the MIC/LINE switches in the LINE position. IMPORTANT: Do not turn the PHANTOM switch on when using unbalanced low-impedance microphones; objec- tionable hum will result. Turn off the PHANTOM switch when condenser microphones are not being used. Use only high-quality cable. Intermittent shorts between broken shield wires and balanced conductors will cause of- fensive noise transients in the system. BATTERY OPERATION AND EXTERNAL POWERING In addition to ac operation, the M267 can be operated from an internal battery pack. Current drain is typically 17 mA at +8 dBm output level and typically 15 mA at + 4 dBm. Battery power is recommended both for remote, on-loca- tion operation, and as an emergency backup source in case of failure of the ac power. Access to the battery compartment is provided at the bottom of the chassis. Three 9-volt alkaline batteries pow- er the M267 at full rated output. Use alkaline batteries for maximum life. Duracell MN1604A or Eveready 522 are recommended. Battery life is approximately 20 hours at +4 dBm continuos use. Note that battery operation with phan- tom power loads and high level headphone monitoring will increase battery drain. With batteries in the battery compartment, the M267 will automatically and silently switch to battery operation should the ac voltage fall below a suitable level. If the ac power fails completely, the VU meter lamps will go out, pro- viding a visual indication of line failure. Battery condition can be determined by using the BATT CHECK switch on the front panel. Activate the BATT CHECK switch and observe the VU meter. A new set of batteries will give about a +2 VU indication. Battery condi- tion is good if the reading is above 0 VU; a lower reading means that new batteries are required for proper opera- tion. Note that the M267 power switch must be turned on to check battery condition. Telephone Interconnection When using the M267 connected directly to a telephone line, check to see whether the local telephone company re- quires an interface coupler between the M267 and the tele- phone line. If a coupler is required, make certain the cou- pler selected and the wiring arrangement are in compliance with the telephone company regulations.

When using the M267 connected directly to a telephone line subject to lightning-induced voltage surges, the follow- ing commercially available part can be installed across the LINE OUT terminals to provide additional protection for output circuit components: Metal Oxide Varistor, General Electric Co., Type No. V22ZA1 ACCESSORIES A268R Rack Panel Kit. The Model A268R Rack Panel Kit includes a 19 in. x 3-1/2 in. (483 mm x 89 mm) precut rack panel and necessary hardware for rack-mounting the M267 (with its cover in place and end caps removed) in a standard 19 in. (483 mm) rack panel. RKC169 Rack Panel Bracket Kit. The Model RKC169 Rack Panel Bracket Kit enables owners of the Shure A68R Rack Panel Kit (originally designed for the M67 and M68 Mixers) to rack-mount the M267 with the A68R. SERVICE WARNING Voltages in this equpment are harzardous! Refer servicing to qualified service personnel. 240 Vac Operation To change the M267 operating voltage from 120 Vac to 240 Vac, follow these steps: 1. Disconnect the M267 from the ac line. 2. Remove the end caps and cover. 3. Locate the voltage selector switch (S201) at the right rear of the main printed circuit board (Figure 3). Move SD201 to the 240V position (toward the front panel). T206 WHT BLK 120V 240V F201 F202 T50/250V 240 V WIRING FIGURE 3 S201 4. Remove fuse F201 (0.1A, 250V, time lag) and replace it with the supplied fuse F202 (0.05A, 250V, time lag). Note that the F202 fuse holder is at right angles to the F201 fuse holder. 5. Replace the ac line cord (if necessary) with one de- signed for the 240 Vac source. If the M267 is to be used outside the U.S. and Canada, local regulations may require replacing the line cord with one having wire insulation colors as follows: “Live” or “Hot” Neutral Earth or Ground U.S., Canada Black White Green Europe Brown Blue Green/ Yellow 6. Replace the cover and end caps, and mark the rear panel to reflect the new operating voltage.

REFERENCE DESIGNATION PART NUMBER DESCRIPTION COMMERCIAL ALTERNATE C101,C209, C219, C227, C232 86T628 Capacitor, Electrolytic, 5 µF, 25V Sprague TVA 1303 C115 86L628 Capacitor, Electrolytic, 250 µF, 50V Sprague 501D227F063PR C201, C204- C205, C208 86V628 Capacitor, Electrolytic, 22 µF, 6.3V Sprague 501D226F016LL C210 86M630 Capacitor, Electrolytic, 10 µF, 25V Sprague TE 1204 C212-C213 86R630 Capacitor, Electrolytic, 68 µF, 25V Sprague 501D686F025MN C215, C218 86L626 Capacitor, Electrolytic, 470 µF, 35V Sprague 503D477F035QE C216, C222 86A630 Capacitor, Electrolytic, 5 µF, 35V Sprague TE1303 C221, C229 86N630 Capacitor, Electrolytic, 22 µF, 35V Mallory F226KM C223 86S628 Capacitor, Electrolytic, 1 µF, 50V Sprague TVA1300 D209, D211-D214, D222-D223, D226-D229 86A415 Diode, Silicon, Computer, 75V TI 1N4148 D210, D217, D230-D235 86A404 Silicon Rectifier, 100V, 1/2A Motorola 1N4002 D218-D221 86A405 Diode, Germanium, 30V RCA 1N48, 1N60 D301 86F422 Diode, Light-Emitting General Instrument MV5075C F201 80F159 Fuse, Slow–Blow, 3AG, 0.1A, 250V Littlefuse 313000 Se- ries F202 80C380 Fuse, Time Lag, 0.05A, 250V Schurter 034.3104 J1 95C450 Jack, Phono Switchcraft 3511A J2A, B 90T2600 Connectors, Binding Post None J101-J104 95B8011 Connector, 3-Pin Female XLR Switchcraft Y3FDPC J105 95B8012 Connector, 3-Pin Male XLR Switchcraft Y3MPC J301 90BJ2600 Phone Jack Switchcraft L-1128PC L101-L113 80A365 Ferrite Bead Ring Panasonic Exc-ELSA35 M1 RKC170 (95A8214) Meter, 190 µA None MP1-MP5 90A8028 Knob, MIC 1-4, MASTER None MP6 90A8029 Knobs, PHONE None MP7 90A8027 Cover, Battery None MP8-MP9 65A8008 End Cap None REFERENCE DESIGNATION PART NUMBER DESCRIPTION COMMERCIAL ALTERNATE PL301-PL302 95A8010 Lamp, 6.3V, 0.2A Sylvania 86 Q201 86A350 Transistor, NPN Motorola 2N5210 Q202, Q204 86A334 Transistor, NPN Rohm TIS92 Q203, Q205 86A348 Transistor, PNP Motorola 2N5087 Q206 86A335 Transistor, PNP Rohm TIS93 Q207 86A8302 Transistor, PNP Motorola TIP30A R250 46A8016 Potentiometer, 100k None R302, R306, R310, R314 46B8000 Potentiometer, 100k None R317 46C8000 Potentiometer, 200k None R322 46D8000 Potentiometer, 5k None S101-S104 55B8008 Switch, Slide, 3PDT None S105, S302, S306 55B8007 Switch, Slide, DPDT None S106-S107, S301, S303-S305 55B8001 Switch, Slide, DPDT None S201 55A8035 Switch, Slide, DPDT Switchcraft EPS1-PC1 S307 90CB2600 Switch, Pushbutton, SPDT Switchcraft 953 S308 55A8009 Switch, Slide, 3PDT None T201-T204 95B8165 Transformer, Input None T205 51E235A Transformer, Output None T206 51A8021 Transformer, Power None U201 86B808A Integrated Circuit, Quad Op Ampl (Selected for NF) Raytheon RC4156N U202 86A8908 Opto-Isolator None U203 86A811A Integrated Circuit, Dual Op Ampl Raytheon RC4559NB U204 86A806A Integrated Circuit, Quad Comparator Raytheon LM339DB U205 86A811A Integrated Circuit, Dual Op Ampl Raytheon RC4559NB U206 86A803 Integrated Circuit, Dual Op Ampl Motorola MC1458C-P1 U207 86B8930 Integrated Circuit, Voltage Regulator National Semiconductor LM317AT W1 90A8045 Line Cord, AC None Parts listed as RKC Kits should be ordered by that kit number.