Shure Brothers Incorporated 222 Hartrey Avenue Evanston IL 60202-3696 U.S.A. Shure SCM268 Mixer SCM268 Four-Channel Microphone Mixer E1998, Shure Brothers Inc. 27A8606 (RD) Printed in U.S.A.
SHURE SCM268 DESCRIPTION The Shure Model SCM268 is a transformer-balanced, fourchannel microphone mixer. Its simple, compact design delivers superior performance and exceptional sound quality with low noise and a flat frequency response. Versatile in all types of applications, the SCM268 integrates transformer-balanced XLR inputs, a switchable microphone/line level transformer-balanced XLR output, phono jack inputs and S S S S output, phantom power, and an auxiliary input channel.
Input Gain GAIN CONTROL Output Gain The gain control knobs 1–4, located on the front panel, adjust the gain for both microphone and auxiliary-level inputs of channels 1–4 (see Figure 1). For example, the channel 1 gain control is used for both the channel 1 microphone input (MIC LEVEL INPUT 1) and the channel 1 auxiliary level input (AUX LEVEL INPUT 1). The auxiliary gain control knob (AUX IN) affects only the auxiliary input (AUX IN).
CONNECTIONS The following diagram illustrates a few of the many types of connections possible with the SCM268. Note that nothing is connected to the channel 4 microphone input (MIC LEVEL INPUT 4). This is because channel 4 is being used for the consumer-level equipment connected to the channel 4 auxiliary level input (AUX LEVEL INPUT 4).
INSTALLATION Supplied Hardware S S S S S S S S 4 rubber feet. For stand-alone installation. 1 rackmount bracket, long. For half-rack (single unit) installations. 1 rackmount bracket, short. For half-rack (single) or dualmount installations. 2 straddle brackets. For dual-mount or fixed installations. 12 bracket screws, 1/4 in. (6 mm). For securing the brackets to the chassis. 4 rackmount screws, 1 in. (2.5 cm). For mounting the unit in a rack. 4 plastic washers. For use with the supplied rackmount screws.
INTERNAL MODIFICATIONS The following table lists the low-cut frequency corners for some of the most common capacitor values: WARNING! Voltages in this equipment are hazardous to life. No user-serviceable parts inside. Refer all servicing to qualified service personnel. Capacitor Value (mF) Low-Cut Frequency Corner (Hz) .033 803 .047 564 .068 390 Disassembly To access the printed circuit board (pc board) for internal modifications, use the following steps: 1. Unplug the power cord. 2.
SPECIFICATIONS Measurement Conditions (unless otherwise specified): Line voltage 120 Vac, 60 Hz (SCM268) or 230 Vac, 50 Hz (SCM268E); full gain; 1 kHz, one channel activated; source impedances: Mic 150 Ω, Aux Level 150 Ω; terminations: Line 600 Ω, Mic 600 Ω, Aux Out 10 kΩ. 12 V phantom power off.
