Shure M268n Schematic

Outputs

	IMPEDANCE
	Designed for	Actual	Output
OUTPUT	Use With	(Internal)	Clipping Level
Low Imp	Any low imp	120	±22 dB
Mic	(19 to 600 )		(100 mV)
	mic circuit
High Imp	Unbal 10 to	5 k	+4.5 dBV
Mic	50 k mic		(1.7 V)
	circuit
Aux	10 k or	2.5 k	18 dBV
	greater		(7.9 V)
	unbalanced
	high-level cir-
	cuits
Mix Bus	3.3 k	3.3 k	±8 dBV
			(0.4 V)

Noise

Equivalent Input Noise: ±128 dBV (low impedance mic 150 - 300-20,000 Hz) at full gain

Equivalent Input Hum and Noise: ±125 dBV (low impedance mic 150 - 20-20,000 Hz) at full gain

Output Noise: ±90 dBV (master control down). ±65 dBV (master up), (input controls down, 300-20,000 Hz)

Output Hum and Noise: ±82 dBV (master down), ±60 dBV (master up) (input controls down, 20-20,000 Hz)

Common Mode Rejection

65 dB minimum with 100 mV input at 100 Hz

Control Interaction

Less than 1 dB with any control combination

Phase

All microphone inputs and outputs in phase; tips of high-impedance inputs and mix bus jack in phase with pin 3; aux input in phase with aux outputs and pin 2

Phantom Power

30 Vdc open circuit, 3.3 k series resistance

Operating Voltage

120 or 240 volts ±10%, 50/60 Hz, 5W, 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 74oC (±20o to 165o F)

Dimensions

See Figure 1.

309 mm			229 mm
(12	5/ in.)		(9 in.)
	32
	68.8mm
	(2 23/	32	in.)
		6.3 mm
		(1/ in. )
			4
	FIGURE 1
Weight
Net:	1.8 kg (4 lb 1 oz)
Packaged: 2.8 kg (6 lb 1 oz)
Certifications

Listed by Underwriters' Laboratories, Inc., and listed by Canadian Standards Association as Certified

CONTROLS AND CONNECTORS

WARNING

This apparatus must be earthed (grounded)! The M268 power supply is energized when the unit is connected to an ac source; disconnect mains (power) plug from supply when not in use.

Inputs

A maximum of four lowand four high-impedance dynamic, ribbon or condenser microphones can be connected to receptacles marked INPUT 1, INPUT 2, INPUT 3, and INPUT 4. The inputs are designed for low-impedance microphones with 19 to 600 impedance, or high-impedance microphones. Both lowand high-impedance microphones can be used simultaneously. Crystal or ceramic microphones are not recommended. The input receptacles are professional three-pin XLR Audio-type connectors, and 1/4 phone jacks. See Figure 2 for lowand high-impedance connections to inputs. Note that some condenser microphones produce very high output signals which may overload the inputs of many mixers; the M268's feedback-type active gain controls virtually eliminate the need for in-line attenuators to compensate for these ªhotº microphones.

	SHIELD			SHIELD
		2	1
			3
MICROPHONE		MIXER INPUT		MICROPHONE	MIXER INPUT
	LOW IMPEDANCE			HIGH IMPEDANCE
	(BALANCED LINE)
	MICROPHONE INPUT CONNECTIONS
	SHIELD			SHIELD
1	2
	3
LOW IMPEDANCE OUTPUT				HIGH IMPEDANCE OUTPUT
(BALANCED LINE)

MICROPHONE OUTPUT PLUG CONNECTIONS

FIGURE 2

2