Shure SCM268E User Manual

Model SCM268E User Guide

1

2

3

4

AUX IN

OUTPUT

LEVEL

METER

MASTER

POWER

-10

0

+6

+12

+18

-20

SCM268 microphone mixer

SCM268E

Four-channel Microphone Mixer

四频道麦克风混音器

4 채널 마이크 믹서

©2008 Shure Incorporated
27AS8880 (Rev. 2)

Printed in U.S.A.

TABLE OF CONTENTS

ENGLISH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

CONNECTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

INTERNAL MODIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

目录

中文. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

连接 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

安装 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

规格 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

목차

한국어 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

연결 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

설치 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

사양 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3

ENGLISH

USE only with a cart, stand, tripod, bracket, or table
specified by the manufacturer, or sold with the
apparatus. When a cart is used, use caution when
moving the cart/apparatus combination to avoid
injury from tip-over.

This symbol indicates that dangerous voltage constituting a
risk of electric shock is present within this unit.

This symbol indicates that there are important operating and
maintenance instructions in the literature accompanying this unit.

! IMPORTANT SAFETY INSTRUCTIONS !

1. READ these instructions.

2. KEEP these instructions.

3. HEED all warnings.

4. FOLLOW all instructions.

5. DO NOT use this apparatus near water.

6. CLEAN ONLY with dry cloth.

7. DO NOT block any ventilation openings. Install in accordance with the manu­facturer's instructions.

8. DO NOT install near any heat sources such as radiators, heat registers, stoves,
or other apparatus (including amplifiers) that produce heat.

9. DO NOT defeat the safety purpose of the polarized or grounding-type plug. A
polarized plug has two blades with one wider than the other. A grounding type
plug has two blades and a third grounding prong. The wider blade or the third
prong are provided for your safety. If the provided plug does not fit into your out­let, consult an electrician for replacement of the obsolete outlet.

10. PROTECT the power cord from being walked on or pinched, particularly at plugs,
convenience receptacles, and the point where they exit from the apparatus.

11. ONLY USE attachments/accessories specified by the manufacturer.

WARNING:

Voltages in this equipment are hazardous to life. No user-serviceable parts inside. Refer all servicing to qualified service personnel. The

12.

13. UNPLUG this apparatus during lightning storms or when unused for long periods of
time.

14. REFER all servicing to qualified service personnel. Servicing is required when the
apparatus has been damaged in any way, such as power-supply cord or plug is dam­aged, liquid has been spilled or objects have fallen into the apparatus, the apparatus
has been exposed to rain or moisture, does not operate normally, or has been
dropped.

15. DO NOT expose the apparatus to dripping and splashing. DO NOT put objects filled
with liquids, such as vases, on the apparatus.

16. The MAINS plug or an appliance coupler shall remain readily operable.

17. The airborne noise of the apparatus does not exceed 70dB (A).

18. Apparatus with CLASS I construction shall be connected to a MAINS socket outlet
with a protective earthing connection.

19. To reduce the risk of fire or electric shock, do not expose this apparatus to rain or
moisture.

20. Do not attempt to modify this product. Doing so could result in personal injury
and/or product failure.

safety certifications do not apply when the operating voltage is changed from the factory setting.

4

DESCRIPTION

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1 2 3 4 5 6 7 8

1

2345678

SHURE SCM268

The Shure Model SCM268 is a transformer-balanced, four-channel 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 output, phantom power,

FEATURES

• Four transformer-balanced microphone inputs

• Transformer-balanced output-switchable mic/line level

• Five -10 dB line-level inputs

• Six-segment LED output level meter

FRONT PANEL

Gain Controls (1-4). Adjusts gain for microphone level

inputs and auxiliary level inputs 1-4.

Auxiliary Channel Gain Control (AUX IN). Adjusts the
auxiliary channel input gain.

Output Meter. LED meter indicates peak output signal
level.

and an auxiliary input channel. It can function as a primary or add-on mix­er for sound reinforcement, recording, broadcast, or audio-visual presen­tation systems.

With the supplied hardware, the mixer's half-rack chassis mounts secure­ly in single or dual rackmount installations. For fixed installations, the
SCM268 can be fastened on or below a shelf, counter, or tabletop.

• Built-in 12-volt phantom power

• Internal power transformer

• Built-in low-cut filter on microphone inputs (below 80 Hz)

Master Gain Control (MASTER). Adjusts overall output
level.

Power Indicator (POWER). This LED illuminates when the
unit is plugged in and receiving power.

NOTE: The SCM268 does not have a power switch. To turn the unit off,
unplug the power cord or use an external power strip with a switch.
However, it can remain plugged in as it uses very little power when idle.

ENGLISH

REAR PANEL

Power Connector. Accepts 100-120 Vac (SCM268) or

220-240 Vac (SCM268E).

Output Connector (MIC/LINE OUT). Transformer-bal­anced XLR output connector. Switchable between line and
microphone level.

Output Level Switch (MIC/LINE OUT). Recessed switch
changes the signal level of the XLR output connector:
In = Microphone Level
Out = Line Level

Auxiliary Output Connector (AUX OUT). Phono jack
feeds consumer-level audio equipment. Not affected by
MIC/LINE switch.

Auxiliary Level Inputs (AUX LEVEL INPUTS, 1-4). Phono
jacks connect to consumer-level audio sources.

Auxiliary Input Channel (AUX IN). A dedicated auxil­iary-level input for the auxiliary channel.

Phantom Power Switch (12V PHANTOM). Recessed
switch turns on phantom power for microphone inputs 1-4.

Microphone Level Inputs (MIC LEVEL INPUTS). Trans­former-balanced, microphone-level XLR inputs.

5

GAIN CONTROL

Channel 1

Channel 3

Channel 2

Channel 4

Master Output

Auxiliary Channel

GAIN CONTROL

FIGURE 1

GREEN-Nominal

RED-Clip

Peak in dBu

Phantom Power Switch

OFF ON

Output Level Switch

LINE MIC

INPUT 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).

ENGLISH

OUTPUT LEVEL METER

The six LEDs on the front panel labeled OUTPUT LEVEL METER illumi­nate to reflect the peak level of the mixed output signal from the SCM268
(in reference to balanced line output) in dBu (0 dBu = 0.775 V).

OUTPUT GAIN

The master output gain control knob (MASTER) adjusts gain to both the
XLR balanced output (MIC/LINE LEVEL) and the auxiliary level output
(AUX LEVEL).

Use the master gain control (MASTER) to adjust peak levels, as indicated
by the LEDs. The red LED illuminates when the output is 2 dB below clip­ping.

PHANTOM POWER

When the phantom power switch on the back panel is on (12V PHAN­TOM-ON), the SCM268 provides 12 V of phantom power to each XLR mi­crophone input. The switch is recessed to prevent accidental
engagement. Most condenser microphones require phantom power. Use
it when connecting these types of microphones to the SCM268.

NOTE: Phantom power does not affect the operation of balanced
dynamic microphones. With phantom power on, they can be connected to
the SCM268 in combination with condenser microphones that do use it.

OUTPUT LEVEL SWITCH

The output level switch on the back panel (MIC/LINE OUT) sets the level
of the balanced XLR output. When set to MIC, it reduces the output by
about 50 dB. Set the switch so that the output level matches the input lev­el of the device to which you are connecting the SCM268. The switch is
recessed to prevent accidental engagement.

NOTE: The output level switch does not affect the auxiliary output (AUX
OUT) level.

6

CONNECTIONS

AUX IN

CONSUMER-LEVEL

EQUIPMENT

CHANNEL 4

CONSUMER-LEVEL

EQUIPMENT

CHANNEL 3

DYNAMIC

MICROPHONE

CHANNEL 2

CONDENSER

MICROPHONE

CHANNEL 1

DYNAMIC

MICROPHONE

CD PLAYER

OR

AM/FM RECEIVER

OR

TAPE DECK

POWER SUPPLY

AMPLIFIER

70 V P.A.

LOUDSPEAKERS

AUX OUT

OR

OR

LINE OUT

VCR

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). Connecting both auxiliary lev­el and microphone level inputs to a single channel is not recommended
because the SCM268 would not be able to independently mix the two
sources.

ENGLISH

7

INSTALLATION

Wood Screw

Rackmount Screw

Bracket Screw

SUPPLIED HARDWARE

•

•

•

•

ENGLISH

•

•

•

•

4 rubber feet.

1 rackmount bracket, long.

lations.

1 rackmount bracket, short.

al-mount installations.

2 straddle brackets.

12 bracket screws, 1/4 in. (6 mm).

to the chassis.

4 rackmount screws, 1 in. (2.5 cm).

a rack.

4 plastic washers.

screws.

4 wood screws, 1/2 in. (1.25 cm).

For stand-alone installation.

For half-rack (single unit) instal-

For half-rack (single) or du-

For dual-mount or fixed installations.

For securing the brackets

For mounting the unit in

For use with the supplied rackmount

For fixed installations.

RACKMOUNT INSTALLATION

The SCM268 can be mounted as a single unit or dual-mounted with either
another SCM268 or another Shure half-rack unit such as the SCM262 or
DFR11EQ.
methods:

1. Attach the short and long rackmount brackets to the SCM268

Attach the rackmount brackets using one of the following

Single unit (half-rack) installation:

with eight (8) of the supplied bracket screws.

2. Attach the short rackmount brackets to the outsides of the com-

bined units with eight (8) of the bracket screws.

3. After attaching the brackets, mount the unit in an equipment rack
using the supplied rackmount screws and plastic washers.

STAND-ALONE INSTALLATION

Adhere the four (4) supplied rubber feet to the bottom of the unit at each
corner. This will keep it from sliding and protect the table surface.

FIXED INSTALLATION

To permanently affix the SCM262 above or below a table, shelf, or
counter top, use the following steps:

1.

Fasten the straddle brackets to the recessed edges of the chassis
using four (4) bracket screws.

Top mount: Fasten the straddle brackets to on the bottom of the unit

Hanging mount: Fasten the straddle brackets to the top of the unit.

2. Fasten the straddle brackets to the surface using the four (4) sup­plied wood screws.

Dual-mounted installation:

1.

Connect the two units together side-by-side using two (2)
straddle brackets. The brackets should straddle the recessed
edges on on the top and bottom of each chassis. Fasten
them using eight (8) bracket screws.

NOTE: Be sure to use both straddle brackets-one on the top and one on
the bottom.

TOP MOUNT

HANGING MOUNT

8

INTERNAL MODIFICATIONS

C 26.5 F⁄=

15 KΩ

0.1 ΜF

WARNI NG! Voltages in this equipment are hazardous to life. No user-serviceable parts inside. Refer all servicing to qualified service personnel.

DISASSEMBLY

To access the printed circuit board (pc board) for internal modifications,
use the following steps:

1.

Unplug the power cord.

2. Remove the knobs and retainer nuts from the front panel (See
Figure 2).

KNOB ASSEMBLY

FIGURE 2

3.

Remove the four screws at each corner of the

back panel.

4. Remove the two screws at each bottom corner of the front panel

5. Slide the back panel and pc board out from the rear of the chas­sis.

CAUTION: When reassembling the SCM268, DO NOT OVERTIGHTEN
the knob retainer nuts. Use a minimal amount of force to secure the nut
(0.6-0.8 N⋅m (5-7 in⋅lb)). Damage to the internal components will result if
too much force is used.

LOW-CUT FILTER

To bypass the built-in low-cut filter for a given channel, remove the spec­ified resistor and place a 10

μ

F to 33μF capacitor in the specified pc board

location (polarity does not matter). Refer to the following table:

Channel Remove Resistor from: Place 10μF to 33μF

1R18 X17
2R28 X27
3R38 X37
4R48 X47

Capacitor in:

To select a particular corner frequency for the low cut filter, remove the
R18, R28, R38, or R48 resistor for a given channel as specified above.
Then, in the corresponding pc board location (X17, X27, X37, or X47),
place a capacitor of the specified value (polarity does not matter). Refer
to the following formula for selecting the correct capacitor value for the de­sired corner frequency.

The following table lists the low-cut frequency corners for some of the
most common capacitor values:

Capacitor Value (μF) Low-Cut Frequency Corner (Hz)

.033 803
.047 564
.068 390

.1 265
.22 120
.33 80
.47 56
.68 39

1.0 26.5

2.2 12

PHANTOM POWER DISABLE

To disable phantom power for a given microphone input, remove the
specified resistor as listed in the following table:

Channel Remove Resistor:

1R15

2R25

3R35

4R45

LINE PAD

To insert a 50 dB line pad for a given microphone input, remove the spec­ified resistor and short the solder points at the specified pc board loca­tions. Refer to the following table:

Channel Remove Resistors: Short Solder Points:

1 R12, R13, R15 X11 and X14
2 R22, R23, R25 X21 and X24
3 R32, R33, R35 X31 and X34
4 R42, R43, R45 X41 and X44

HOT MIC PAD

Some condenser mics have a high output. In order to avoid overdriving
the input stage, the user may need to set the input pot lower than desired.
To fix this problem, the user can place an 11 dB pad into the input gain
stage of a selected channel.

1.

Twist together the leads from one side of a 15 k

Ω resistor and a

0.1 μF capacitor:

ENGLISH

where:

C = value of capacitor in μF
F = corner frequency (-3 bB) for low-cut filter in Hz

2. Solder the free ends of the resistor-capacitor combination into the
holes at the jumper position indicated by the following table and
remove the corresponding surface mount resistor.

Channel Remove

1R18 X17
2R28 X27
3R38 X37
4R48 X47

9

Resistor

Insert Resistor-Capacitor

Combination at Jumper

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.

Frequency Response (Ref 1 kHz, controls centered)

Low-Cut Filter (Microphone inputs only)

ENGLISH

Gain (typical, controls full clockwise)

Low-impedance mic

Inputs

Outputs

Total Harmonic Distortion

Equivalent Input Hum and Noise(150 Ω source; through 22
Hz—22 kHz filter)

Output Hum and Noise (through 22 Hz—22 kHz filter; chan­nel controls full counterclockwise)

Common Mode Rejection

Microphone Inputs: 150 Hz to 20 Khz ±2 dB (built-in 80Hz
low-cut)
Auxiliary Inputs: 20 Hz to 20 kHz ±2 dB

3dB down at 80 Hz, 6 dB/octave

Input Output

Mic Line Aux Out

(150 Ω)

Aux Level 3 dB 40 dB 29 dB

Input Impedance

Mic 19-600 Ω 1.2 kΩ –5 dBV

Aux Level

Output Impedance

Mic low-Z inputs 0.2 Ω –21 dBV

Line >600 Ω 72 Ω +18 dBV

Aux Out >2 kΩ 870 Ω +7 dBV

38 dB 76 dB 65 dB

Designed for

use with

≤2 kΩ

Designed for

use with

Actual

(typical)

21 kΩ >28 dBV

Actual

(typical)

Input

Clipping Level

Output

Clipping Level

<0.25% at +4 dBu output level (through 22 Hz—22 kHz filter;
Input 1 and Master centered, all other controls full counter­clockwise)

124 dBV

Master full counterclockwise: –92 dBV
Master full clockwise: –70 dBV

>80 dB at 1 kHz

Polarity

All inputs to all outputs are non-inverting

Overload and Shorting Protection

Shorting outputs, even for prolonged periods, causes no dam­age. Microphone inputs are not damaged by signals up to +10
dBV; Auxiliary inputs by signals up to +36 dBV

Phantom Power

12 Vdc open-circuit through 340Ω series resistance

Operating Voltage

SCM268: 100—120 Vac rated nominal, 50/60 Hz, 60 mA
SCM268E: 220—240 Vac rated nominal, 50/60 Hz, 30 mA

Temperature Range

Operating: –7° to 49° C (20° to 120° F)
Storage: –29° to 74° C (–20° to 165° F)

Overall Dimensions

44 mm H x 218 mm W x 162 mm D
(1.72 x 8.60 x 6.37 inches)

Net Weight

1.20 Kg (2 lbs, 10 oz)

Certifications

SCM268: UL & cUL LISTED by Underwriters Laboratories, Inc.
SCM268E: Eligible to bear CE Marking. Conforms to European
EMC Directive 89/336/EEC. Meets applicable tests and perfor­mance criteria in European Standard EN55103 (1996) parts 1
and 2, for residential (E1) and light industrial (E2) environ­ments.

N 108

Replacement Parts

Knob, Master (blue) ...............................................95B8752

Knob, Channel Gain (white)................................... 95A8752

Line (Power) Cords:

SCM268: 100-120 Vac (US/Canada)................ 95A8762

SCM268E: 220-240 Vac (EU) ........................... 95A8778

SCM268E (Australia/New Zealand) .................. 95A9128

Fuse, SCM268 (5x20 mm,

250V, 80mA, slow-blow)........................................... 80A730

Fuse, SCM268E (5x20 mm,

250V, 40mA, slow-blow)............................................80J258

Hardware Kit ........................................................ 90AF8100

Link Bars (Bracket) ................................................ 53A8443

Single Mount Bracket ............................................. 53A8484

Dual Mount Bracket ............................................... 53B8484

Optional Accessories

Line (Power) Cord, 230-240 Vac (UK) ................... 95A8713

10

SHURE Incorporated http://www.shure.com
United States, Canada, Latin America, Caribbean:
5800 W. Touhy Avenue, Niles, IL 60714-4608, U.S.A.
Phone: [phone] U.S. Fax: [phone] Intl Fax: [phone]
Europe, Middle East, Africa:
Shure Europe GmbH, Phone: [phone] Fax: [phone]
Asia, Pacific:
Shure Asia Limited, Phone: [phone] Fax: [phone]

전화

: 847-600-2000

Shure Europe GmbH,

Shure Asia Limited,

SHURE Incorporated http://www.shure.com

5800 W. Touhy Avenue, Niles, IL 60714-4608, U.S.A.

미국 팩스 :

미국 , 캐나다 , 중남미 , 카리브해 지역 :

847-600-1212

전화 :

49-7131-72140

전화 :

852-2893-4290

국제 팩스 :

유럽 , 중동 , 아프리카 :

팩스 :

49-7131-721414

아시아 , 태평양 :

팩스 :

847-600-6446

852-2893-4055

SHURE Incorporated http://www.shure.com

美国、加拿大、拉丁美洲、加勒比海地区：

5800 W. Touhy Avenue, Niles, IL 60714-4608, U.S.A.

电话：

847-600-2000

欧洲、中东、非洲：

Shure Europe GmbH

亚太地区：

Shure Asia Limited

美国 传真：

，电话：

，电话：

847-600-1212

49-7131-72140

852-2893-4290

国际 传真：

传真：

传真：

852-2893-4055

847-600-6446

49-7131-721414