Shure M677 Schematic

Distortion

Less than 1% Total Harmonic Distortion at 1,000 Hz when Low lmpedance Microphone Output is at 20 mV level, High lmpedance Microphone Output is at 300 mV level, and MIX BUS AND AUX OUTPUT is at 2V level (loaded with 47 kilohms).

lnput Clipping Level

	Minimum Clipping Level
Low lmpedance
Microphone Input	25 mV (-32 dBV)
Line Input	lOV (+20 dBV)

Minimum Common Mode Rejection

110	dB with microphone input of 10V at 100 Hz
Output Clipping Level		Minimum Clipping Level
Low lmpedance		25 mV (-32 dBV)
Microphone Output
High Impedance		0.4V	( - 8 dBV)
Microphone Output
Mix	Bus and	0.4V	( -8 dBV) (3.5K load)
Aux	Output	3V ( +10 dBV) (47K load)

Phase

The Mix Bus and Aux, and Microphone Level (High Impedance) Outputs are in phase with pin 3 of each input connector. The Microphone Level (Low Impedance) Output is in phase with each input.

Lo-Cut Filters

- 6 dB at 100 Hz typical

Volume Controls

All audio taper

Operating Voltage

27 Vdc, 6.0 t 2 mA. (Meets all specifications except clipping levels at any voltage from 20 to 34 Vdc)

Temperature Range

Operating: -7" to 57°C (20" to 135°F) Storage: -29" to 71"C (-20" to 160°F)

Dimensions

See Figure 1

	OVERALL DIMENSIONS
Net Weight	FIGURE 1
1.7 kg (3% lb)

INSTALLATION AND OPERATION

INPUTS

A maximum of six low-impedance dynamic, ribbon or condenser (capacitor) microphones may be connected to receptacles marked INPUT 1 through INPUT 6. With MICILINE switches set to MIC, the inputs will accept signals from the above microphones or micro- phone-level signals such as the low-impedance microphone-level outputs of mixers. With MICILINE switches set to LINE, the inputs will accept balanced 600-ohm line-level signals.

30 VDC: The attached cables and rear-panel jacks supply 20 to 34 Vdc (6.0 mA at 27 Vdc) from an associated Shure mixer to power the M677. In addition, the M677 may be powered from a Shure A67B battery power supply. NOTE: For use with Shure M68 Series Mixers, connect only the red 30 VDC cable to the M68; ground connection is provided through the phono or microphone cable.

CAUTION: If the A678 is used, the M677'sattached power cables should be insulated to avoid accidental shorting or grounding.

OUTPUTS

MIC OUTPUTS: The receptacle marked MIC OUTPUT has either lowor high-impedance microphone-level output selected by the switch above the receptacle. This output is designed for connection to a 25 to 600 ohm microphone input or to a high-impedance microphone input of an amplifier or tape recorder. (This output may be used simultaneously with the MIX BUS AND AUX OUTPUT connector.) See section on CONNECTIONS for instructions on connection to a highor low-impedance balanced or unbalanced line.

MIX BUS AND AUX OUTPUT: It is important to note that both mix bus and aux output functions are fed through the same connector. The unusual circuit design associated with this output enables it to be connected to a mixer, tape recorder or amplifier aux input (47 kilohms) or a Shure mixer mix bus (3.5 kilohms). This connector cannot be used to drive both a mix bus and aux input at the same time, because connection to a mix bus (about 3.5 kilohms) will reduce the signal at this connector to a level which is too low for most aux inputs. Note that when connected to an AUX input, the MIX BUS AND AUX OUTPUT connector cable should be 3m (10 ft) maximum; when connected to a mix bus input, the cable may be up to 30m (100 ft).

For mix bus connections such as stacking several M677's,this jack may be used with the supplied phono pin connector cable and a "Y" adapter. If this jack is to be used to drive more than one input, a "Y" adapter should also be used. See section on CONNECTIONS for instructions on connection to mating phono plug.

30 VDC: The rear-panel 30 VDC jacks may be used as output jacks to provide power to an additional M677 (as well as input jacks from an external battery supply) when the M677 is powered through the 30 VDC attached cable connectors.

CONNECTIONS

The microphone inputs and output are three-pin professional connectors (designed to mate with Cannon XL series, Switchcraft A3 (Q.G.) series or equivalent). A mating three-pin professional male connector (to