Shure M688 Schematic

INSTALLATION:

CONNECTION BETWEEN COMPONENTS

For balanced-line connection use two-conductor, shielded, low-capacity cable. For unbalanced (highimpedance) connection, use single conductor, shielded, low-capacity cable.

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-------	MIC. INPUT			\1------/
MICROPHONE			MICROPHONE		MIC. INPUT
LOW IMPEDANCE				HIOH	IMPEDANCE
(BALANCED LINE)
MICROPHONE		INPUT	PLUG	CONNECTIONS
					SHIELD
2
MIC. OUTPUT			MIC.OUTPUT
LO W IMPEDANCE				HIGH IMPEDANCE
(BALANCED	LINE)	OUTPUT PLUG
MICROPHONE				CONNECTIONS

MICROPHONE CONNECTIONS - FIGURE B

INPUT CONNECTIONS

Microphones: A maximum of four low or high-imped- ance dynamic, ribbon, or capacitor (condenser) microphones may be connected to receptacles marked Mic. 1, Mic. 2, Mic. 3 and Mic. 4. The inputs are designed for low-impedance microphones with 25 to 600 ohms impedance or high-impedance microphones, as selected by a slide switch above the input receptacle. The unit is not recommended for use with crystal or ceramic microphones. The input receptacles, Mic. 1, Mic. 2, Mic. 3 and Mic. 4 are female professional three-pin audio connectors* (mate, Shure Part 95A407). See Figure B for low-and high-impedance connections to receptacle.

(NOTE: Some capacitor (condenser) microphones produce very high output signals which may overload the input of a mixer. A Shure Model A15A Microphone Attenuator placed between the microphone and the mixer input will eliminate this problem.)

Aux. Input: The left channel (L) and right channel (R) phono jacks marked Aux. Input on the rear panel will accept the output from a high-impedance, high-level source such as a tape recorder, AM-FM tuner, or output from a phono cartridge preamplifier, such as the Shure Model M64 or A68P (2 Model A68P'srequired for Stereo). One or more Shure M68 Series Microphone Mixers may be connected to these jacks to add additional microphone inputs.

Mix Bus: The left channel (L) and right channel (R) phono jacks marked Mix Bus on the rear panel are used when paralleling M688 units to increase the number of input channels. Use a phono pin plug jumper cable between each L Mix Bus jack, and another between each R Mix Bus jack.

OUTPUT CONNECTIONS

Auxiliary Output: The left channel (L) and right channel (R) phono jacks marked Auxiliary Output are highimpedance high-level outputs designed primarily to feed power amplifiers requiring 0.1 to 2 volts, or the auxiliary or tuner inputs of an amplifier or tape recorder.

Mono Mic. Output: The receptacle marked Mono Mic. Output has a lowor high-impedance output selected

*Designed to mate with Cannon XL series, Switchcraft A3 (Q.G.) series, or equivalent connector.

by the switch above the receptacle. This output is the "Mixed" (L + R) monaural output of all the input sources and is designed to work into a 25 to 600 ohm mic. input, or into a high-impedance amplifier or tape recorder microphone input. The receptacle is a male professional three-pin audio connector.' SeeFigure B for output receptacle connections.

30 V.D.C.: These rear panel jacks provide 27 Vdc open circuit (21 Vdc at 5 mA max.) for accessories. An external battery pack, such as the Shure Model A67B or A68B, or an external 26 to 30 Vdc source may also be used to power the M688 via these jacks.

OPERATION

Power: Connect the three conductor power line cord to a 120 volt, 50/60 Hertz ac power outlet. The power ON-OFF switch is on the front panel. A neon pilot lamp indicates that the ac power is on. (This lamp does not light when the unit is battery operated). If battery operation is desired, do not connect line cord. The ON-OFF switch also controls battery input power.

Volume Controls: The Master volume control and the individual volume controls for each of the five channels are identified on the front panel. Both the Aux. volume control and the Master volume control are clutched dual concentric controls. The left channel (L) control is the large outer knob. The right channel (R) control is the smaller inner knob. The relative setting of the left and right controls may be changed by restraining one knob and moving the other. Above the Master volume control is a Mono-Stereo switch used for selecting either monaural or stereo output at the Auxiliary Output L and R jacks on rear of chassis. Individual channel volume controls not being used should be kept at minimum setting (fully counterclockwise).

Mic. 4 Pan Control: The Mic. 4 Pan Control on the front panel is used for adjusting the apparent location of the Mic. 4 Signal to either left or right positions or anywhere between. When the Mic. 4 Pan Control is in the maximum left position, program material on Mic. 4 appears only at the Auxiliary Output left channel (L); likewise, when the Mic. 4 Pan Control is in the maximum Right position, the program material appears only at the Auxiliary Output right channel (R). When the Mic. 4 Pan Control is centered between Left and Right, the Mic. 4 program material appears equally on both left (L) and right (R) Auxiliary Output phono jacks. The program material on Mic. 4 appears at the Mono Mic. Output no matter where the Pan Control is set. In making a stereo recording or with a stereo sound reinforcement system, it may be desirable to place the vocalist on Mic. 4 so the voice may be "centered" between the left (L) and right (R) stereo channels containing the orchestra.

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.