Shure M68RM User Guide

222

HARTREY AVE., EVANSTON. l L.

MICROPHONES AND

AREA CODE 312/328-9000 . CABLE: SHUREMICRO

ELECTRONIC

60204 U.S.A.

COMPONENTS

DATA

SHEET

MODELS M68RM

AND M68RM-2E

MICROPHONE MIXERS

GENERAL:

The Shure Models M68RM and M68RM-2E are fourchannel, completely transistorized portable microphone mixers with built-in REVERBERATION for use with sound reinforcement, tape recording, and audio-visual systems.

The Mixers feature:

Adjustable REVERBERATION to simulate natural reverberation or echoes of a large concert hall. Phone jack provided for use with remote reverberation ON-OFF switch.

Four microphone inputs with individual slide switches mounted on rear panel for selection of low impedance (balanced or unbalanced) or high impedance (unbalanced).

One high level auxiliary input suitable for tape,

tuner, and accessories. (Uses MIC.

input.) Individual volume controls to balance each of the four inputs. Master volume control to simultaneously control level of all inputs. High- (unbalanced) or low-impedance (balanced

or unbalanced) microphone level output. Impedance selected with slide switch to match the microphone input of associated amplifier.

High-impedance auxiliary output.

DC power supply jack. This jack supplies 28 volts dc for use with accessories such as the Model A68P Phono Preamplifier, Model M62V Level-Loc or may be used as power input in connection with the Model

A67B Battery Power Supply (accessory). Facility for connecting two or more mixers together to obtain additional microphone inputs.

For example, two mixers connected together will give a total of seven microphone inputs, or six microphone inputs and one auxiliary input. Listing by Underwriters' Laboratories, Inc.; and

by Canadian Standards Association as certified.

(Applies to Model

M68RM).

SPECIFICATIONS

Gain:

Low Imp.

High

AUX.

27A874

At 1,000 Hz

INPUTS

Mic.

.5 mV produces .8 mV 13 mV Imp. Mic. -18dB f6dB

5 mV produces .63 mV 10 mV

mV produces .63 mV

5..*M

(7,,i.iJ

Overall Dimensions

1968,

(MG)

Shure Brothers

Low

Mic. Mic.

-38

FIGURE

Inc.

OUTPUTS

Imp.

High

dB +28 dB

dB -14 dB +14 dB

FRICTlONlL

Imp.

High

Aux.

+56 dB

320

f34 dB

250

mV 250 mV

DIMENSIONS

lbgn

Imp.

REAR

VIEW

MODEL

M68RM

Frequency Response:

The frequency response is flat 1-3 dB from 40 Hz to 20,000 Hz

Hum-Noise:

70 dB below rated output. (Aux. Output)

Equivalent lnput Noise:

150 ohm source, 123 dB below 1 volt, at full gain.

lnput Impedance:

Microphone inputs suitable for high- or low-imped-

ance dynamic, ribbon, or condenser microphones.

Auxiliary-50,000 ohms.

Recommended Load Impedance:

Low-impedance microphone. 25 to 600 ohms High-impedance microphone. 20,000 ohms or greater

Auxiliary high-impedance. . . .50,000 ohms or greater

Distortion:

Less than

l0lo

total harmonic distortion when lowimpedance microphone output is at 10 mV level, high-impedance microphone output is at 100

mV level, and Aux. high-impedance output is at 1.0 volt level.

Phase:

All microphone inputs and outputs are in phase. Aux. lnput and Output are out of phase with Pin 3 of the microphone connectors.

Output Clipping Level:

Output Min. Clipping Level

Mic. Low Impedance 60

mV Mic. High Impedance .85V Aux. High lmpedance 4.OV

Operating Voltage:

Model M68RM: 120 volts &lo%, 50/60 Hz Model

M68RM-2E: 220-260 volts, 50/60 Hz

Temperature Range:

Operating: -7°C to 57°C (20°F to 135°F) Storage:

-29°C to 71°C (-20°F to 160°F)

Dimensions:

See Figure A.

Weight:

2.33 Kg

Ib, 2 oz)

INSTALLATION:

CONNECTION BETWEEN COMPONENTS

For balanced-line connection use two-conductor,

shielded, low-capacity cable. For unbalanced

(high-

impedance) connection, use single-conductor, shielded,

low-capacity cable.

GROUNDING

If there should be objectionable hum, connect the metal chassis of the mixer to a good ground such as a metal frame of a wall outlet or a water or steam pipe.

This is normally accomplished automatically through

the ground wire of the power cord.

INPUT CONNECTIONS

Note:

Before using mixer remove shipping screw

(located at top of chassis) holding small tag.

Printed

U.S.A.

Microphones: A maximum of four low- or high-impedance dynamic, ribbon or condenser microphones may be connected to receptacles marked MIC. 1, MIC. 2, MIC.

MIC.

The inputs are designed for low-impedance microphones with 25 to 600 ohms impedance or high-impedance microphones. Both low-impedance and high-impedance microphones may be used simultaneously with the

M68RM. The unit is not recommended for use with crystal or ceramic microphones. The impedance is selected by a slide switch above each input receptacle. The input receptacles are professiona'l three-pin female audio connectors.? See Figure B for low- and high-impedance connections to receptacle.

Note: Some condenser microphones produce very high output signals which may overload the input of a mixer.

pj?Fl!LQ.w KyEIELD-m

.,.----

MICROPHON~

LOW IMPEDANCE HIGH IMPEDANCE

(BALANCED LINE)

MIC OUTPUT MIC. OUTPUT

LOW IMPEDANCE

(BALANCED LINE

MIXER

INPUT

MICROPHONE MIXER

MICROPHONE INPUT CONNECTIONS

MICROPHONE OUTPUT PLUG CONNECTIONS

)

Microphone Connections

FIGURE

HIGH IMPEDANCE

SHIELD

INPUT

Auxiliary: The phono jack on the rear of the panel marked AUX. INPUT will accept output from a highlevel source such as a tape recorder, AM-FM tuner,

or output from the Model amplifier (accessory). In this case use MIC. control to control volume of Auxiliary Input. this jack automatically disconnects the MIC.

A68P Phono Cartridge Pre-

gain

(Use of

re-

ceptacle.)

OUTPUT CONNECTIONS

Microphone: The receptacle marked MIC. OUTPUT is a dual-impedance output selected by the switch

above the receptacle. This output is the "mixed" output of all the input sources and is designed to work into a 25- to 600-ohm MIC. line or input, or into a high-impedance amplifier or tape recorder microphone input. The receptacle is a professional three-pin male Sudio connector.+ See Figure B for output receptacle connections.

Auxiliary: The phono jack marked AUX.

HlGH LEVEL OUTPUT is a high-impedance, high-level output designed primarily to feed a power amplifier requiring

0.5 to 2 volts or the auxiliary or tuner input of an am-

plifier or tape recorder.

Accessory 28-volt DC: The terminals marked 28 VOLTS DC sories such as the Model amplifier or the used as a power input when using the Model

and

(-)

provide 28 volts dc for acces-

A68P Phono Cartridge Pre-

M62V Level-Loc. The jacks are also

A67B

Battery Power Supply (accessory).

REVERBERATION

The blue control knob (on front panel) marked

REVERBERATION is used to adjust the amount of

reverberation for the desired effect.

The standard phone jack (on back panel) marked REVERBERATION REMOTE SWITCH is used to connect an ON-OFF switch which can be operated through a cable at a remote location to turn REVERBERATION on and off. See Figure C for switch con-

nections.

Designed to mate with Cannon (Q.G.)

series or equivalent connector.

(male)].

series, Switchcraft

[Shure part

95A407

For best results the cable should be low capacity, single conductor, shielded cable with the shield connected to the sleeve of the phone plug.

SWITCH PHONE PLUG

SHIELD

Remote Reverberation On-Off Circuitry

FIGURE C

SLEEVE

CAUTION: The M68RM Mixer should not be set on or mounted against a loudspeaker, as vibrations from the speaker cabinet may cause improper operation of reverb. Avoid accidental jarring during operation.

OPERATION

Power: Connect the Microphone Mixer power line

-t

cord to a 120 volts (220-260 volt,

50/60 Hz for M68RM-2E).

lo%, 50/60 Hz power source.

Volume Controls: Each input has a separate gain control for balancing sound levels between microphones. The MASTER gain control simultaneously adjusts the level of all inputs.

The individual gain controls should generally be set near maximum (fully clockwise) and the master gain control adjusted to required output. Individual channel gain controls not being used should be kept at minimum gain (fully counterclockwise).

Identifying Controls: Pressure-sensitive adhesive labels are supplied with the Mixers as a means of identifying the control and recording the control posi-

tion when optimum results have been obtained. The labels are easily removed when their use is no longer

required.

OPTIONAL ACCESSORIES

Battery Power Supply

Output Cable Kit

Locking Panel Phono Preamp Rack Panel Kit Stacking Kit HandleITilt Stand

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Attache Carrying Case

Interconnecting Cable

...........................

.........................

...........................

Model A67B Model A68C Model A68L Model A68P Model A68R Model A68S Model A67H Model AC60 Model A68SC

CONNECTING TWO UNITS TOGETHER

A M68RM Reverberation Mixer and a Shure M68

series five-channel Mixer may be combined to give a total of eight microphone channels. In this case, four channels could have reverberation and four channels would NOT have reverberation.

Unit

1-M68RM

Unit 2-M68

A. Connect the AUX.

UNlT

to the AUX. INPUT OF UNlT

HlGH LEVEL OUTPUT of

B. Connect the microphones to mixers and set

each input gain control to

position.

C. Take the output signal for recorder or PA am-

plifier from the appropriate output jack on UNlT 2.

Set Master Control UNlT 1 to position

#4.

E. Set AUX. Control on UNlT 2 to position #lo. F. The Master Control on UNlT 2 is now the Master

for all inputs.

G. Advance Master Control (UNIT 2) to about

#5 position and adjust individual microphone controls for proper level. If overall gain is too low or too high the Master Control (UNIT 2) may be adjusted.

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