Shure M68P Schematic

222 HARTREY AVE . EVANSTON, IL 60204 U S A

	MICROPHONES AN0 ELECTRONIC COMPONENTS	MODEL M68P
		MICROPHONE MIXER
	@ A R E A C O D E 3 1 2 / 3 2 8 9 0 0 0 CABLE SHUREMICRO 1:/ET

GENERAL

The Shure Model M68P is a five-channel, completely transistorized, portable microphone mixer for use with sound reinforcement, tape recording and audio-visual systems.

The Mixer features:

wA high-impedance (unbalanced) microphone level

output.

Four microphone inputs for high-impedance (un-

balanced) microphones.

mOne high-level auxiliary input suitable for tape, tuner, and accessories such as the A68P Phono Preamplifier.

Individual volume controls to balance each of the

five inputs.

w A master volume control to simultaneously control level of all inputs.

wA low-impedance (balanced or unbalanced) rnicrophone level output.

A high-impedance, high-level auxiliary output.

A dc power supply jack. This jack supplies 28 volts dc for use with accessories such as the Model A68P Phono Preamplifier or M62V LevelLoc or it may be used as power input in connection with the Model A67B Battery Power Supply (Accessory).

A facilitv for connectina two or more mixers together i o obtain addithnal microphone inputs. For example, two mixers connected together will give a total of eight microphone inputs and one auxiliary input.

Listing by Underwriters' Laboratories Inc. and listing by Canadian Standards Association as certified.

SPECIFICATIONS

Gain

OUTPUT	DESIGNED FOR USE WITH	ACTUAL IMPEDANCE
Low Imp. Mic.	Balanced or unbalanced	150-300 ohms*
	25 to 600 ohm
	microphone-level circuits
High Imp. Mic.	Unbalanced 10 to 50	30-40 kilohms*
	kilohm microphone-level
	circuits
Auxiliary	Unbalanced high-imped-	2.5-3 kilohms*
	ance (10 kilohms or
	greater) auxiliary circuits
* Depending upon	control settings

Distortion

Less than 1% total harmonic distortion when lowimpedance microphone output is at 20 mV level, high-impedance microphone output is at 200 rnV level, and auxiliary output is at 2.0 volt level.

Phase

All microphone inputs and outputs are in phase. Auxiliary input and output are out of phase with the microphone inputs and outputs.

Clipping Levels, Minimum
Input		Clipping Level
Microphone		450	mV
Output		Clipping Level
Microphone,	High Imp.	850	mV
Microphone,	Low Imp.	60	rnV
Auxiliary		4 volts

Operating Voltage

108-132 volts, 50160 Hz, 3 watts

At 1,000 Hz

OUTPUTS

INPUT

Mic.

Mic.

D.C. Operation

28 volts dc a20%, 5 mA

Dimensions

	Microphone			See Figure A
	5 mV	produces
	Auxiliary
	50 mV	produces
	Frequency Response			Overall Dimensions :;;;";,
	Flat within +3 dB from 40 Hz to 20,000 Hz
	Hum and Noise
	70 dB below rated output (Aux. Output)			FIGURE A
	Equivalent lnput Noise			Net Weight
				1.25 kg (2% Ib)
	33 kilohm source, 103 dB below 1 volt
	Impedance			INSTALLATION
'v	INPUT	DESIGNED FOR USE WITH	ACTUAL IMPEDANCE	Connection Between Mixer and Components
			--;
	Microphone	Unbalanced 10 to 50	60 kilohms	For balanced-line microphone level output connec-
		kilohm microphones		tion, use two-conductor, low capacity shielded cable.
	Auxiliary	100 ohm to 10 kilohm	40-70 kilohms*	For unbalanced (high-impedance) microphone level or
		unbalanced high-level		auxiliary high-level output connection, use single-con-
		sources		ductor, low capacity shielded cable.
	Copyright 1972, Shure Brotherj Inc.			Printed in U.S.A.
	27A545 (NG)

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

Microphones: A maximum of four high-impedance dynamic, ribbon, or condenser microphones may be connected to the standard Y4" phone jacks marked MIC. 1, MIC. 2, MIC. 3, MIC. 4. The microphone inputs may be converted for use with low-impedance microphones by utilizing accessory plug-in transformers Model A95 Series. The unit is not recommended for use with crystal or ceramic microphones.

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

Auxiliary: The phono jack on the rear of the panel marked AUX. INPUT will accept output from a highimpedance, high-level source such as a tape recorder, AM-FM tuner, or output from the Model A68P Phono Preamplifier (accessory). The Model A68M Microphone Preamplifier (accessory) may be connected to this jack to provide a fifth microphone input.

OUTPUT CONNECTIONS

Low lmpedance Microphone: The receptacle marked LO IMP. MIC. OUTPUT is a low-impedance microphone level output. This output is the "mixed" output of all the input sources and is designed to work into a 25 to 600-ohm microphone line or into a low-imped- ance amplifier or tape recorder microphone input. The receptacle is a professional three-pin audio connector (male).? See Figure B for output receptacle connections.

SHIELD
SLEEVE -----
TIP j	2	._-d_--
\-----
MIC. OUTPUT		MIC. OUTPUT
HIGH IMPEDANCE		LOW IMPEDANCE
		(BALANCED LINE)

Microphone Output Connections

FIGURE B

High lmpedance Microphone: The phone jack marked HI IMP. MIC. OUTPUT is a high-impedance microphone level output. This output is, also, the "mixed" output of all sources, designed to work into a high-impedance amplifier or tape recorder microphone input. See Figure B for output jack connections.

NOTE: The highand low-impedance microphone outputs may be used simultaneously.

Auxiliary: The phono jack marked AUX. 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 to an amplifier or tape recorder. This output will also drive the input of the Model M63 Audio Master.

Accessory 28-volt dc: This rear panel jack marked ACCESSORY 28 V.D.C. provides 28 volts dc for accessories such as the Model A68P Phono Preamplifier, Model A68M Microphone Preamplifier or M62V LevelLoc. The jack is also used as the power input when using the Model A67B Battery Power Supply (accessory) for battery operation of the M68P Mixer.

?Designed to mate with Cannon XL series, Switchcraft A3 (Q.G.) series or equivalent connector. [Shure part 95A548 (female)].

OPERATION

Power: Connect the Microphone Mixer power line cord to the proper ac power outlet. See Operating Voltage under Specifications. The M68P has a three-conductor cable with a three prong plug.

Volume Controls: The MASTER gain control and the individual gain controls for each of the five channels are identified on the front panel.

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 each control and recording that controls position when optimum results have been obtained. The labels are easily removed when their use is no longer required.

CONNECTING TWO UNITS TOGETHER

Two M68P Mixers may be combined to give a total of eight microphone channels plus an auxiliary input.

A.Connect the AUX. OUTPUT of Unit 1 to the AUX. INPUT of Unit 2.

6.Connect microphones to mixers and set each mi-

crophone input control to # O position.

C.Take the output signal for recorder or P.A. amplifier from the appropriate output jack on Unit 2.

D.	Set	MASTER control on Unit 1 to position #4.
E.	Set	AUX. control on Unit 2 to position # l o .

F.The MASTER control on Unit 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.

H.If an input to the auxiliary channel is needed, such as for a tape recorder or tuner, use AUX. INPUT on Unit 1. Use AUX. control on Unit 1 for level adjustment of the auxiliary source. The master gain control for the entire system is the MASTER control on Unit 2.

The Model A68S Stacking Kit includes stacking brackets for attaching the two mixers firmly together plus the required inter-connecting cable. The cable only, is available separately under the Model A68SC.

GUARANTEE

This Shure product is guaranteed in normal use to be free from electrical and mechanical defects for a period of one year from the date of purchase. Please retain proof of purchase date. This guarantee includes all parts and labor.

SHIPPING INSTRUCTIONS

Carefully repack the unit and return it prepaid to the factory. If outside the United States, return the unit to your dealer or Authorized Shure Service Center for repair. The unit will be returned to you prepaid.

OPTIONAL ACCESSORIES

Battery Power Supply . . . . . . . . . .	Model A67B
Output Cable Kit . . . . . . . . . . . . . . .	Model A68C
Locking Panel . . . . . . . . . . . . . . . . .	Model A68L
Phono Preamp . . . . . . . . . . . . . . . . .	hlodel A68P
Rack Panel Kit . . . . . . . . . . . . . . . . .	Model A68R
Stacking Kit . . . . . . . . . . . . . . . . . . .	Model A68S
Interconnecting Cable . . . . . . . . . .	Model A68SC
Attache Case . . . . . . . . . . . . . . . . . .	Model AC60
Handle/Tilt Stand . . . . . . . . . . . . . .	Model A67H
Line Matching Transformer . . . . . .	Model A95 Series
Microphone Preamplifier ....... .	Model A68M