Model SCM268E User Guide
ER
AST
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268
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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.
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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
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ENGLISH
! IMPORTANT SAFETY INSTRUCTIONS !
1.
2.
3.
4.
5.
6.
7.
READ these instructions.
KEEP these instructions.
HEED all warnings.
FOLLOW all instructions.
DO NOT use this apparatus near water.
CLEAN ONLY with dry cloth.
DO NOT block any ventilation openings. Install in accordance with the manu-
facturer's instructions.
DO NOT install near any heat sources such as radiators, heat registers, stoves,
or other apparatus (including amplifiers) that produce heat.
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 out-
let, consult an electrician for replacement of the obsolete outlet.
USE only with a cart, stand, tripod, bracket, or table
12.
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.
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 dam-
aged, 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.
8.
9.
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.
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.
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.
This symbol indicates that there are important operating and
maintenance instructions in the literature accompanying this unit.
This symbol indicates that dangerous voltage constituting a
risk of electric shock is present within this unit.
WARNING: Voltages in this equipment are hazardous to life. No user-serviceable parts inside. Refer all servicing to qualified service personnel. The
safety certifications do not apply when the operating voltage is changed from the factory setting.
4
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SHURE SCM268
DESCRIPTION
The Shure Model SCM268 is a transformer-balanced, four-channel mi-
crophone mixer. Its simple, compact design delivers superior perfor-
mance and exceptional sound quality with low noise and a flat frequency
response.
and an auxiliary input channel. It can function as a primary or add-on mix-
er for sound reinforcement, recording, broadcast, or audio-visual presen-
tation systems.
With the supplied hardware, the mixer's half-rack chassis mounts secure-
ly in single or dual rackmount installations. For fixed installations, the
SCM268 can be fastened on or below a shelf, counter, or tabletop.
Versatile in all types of applications, the SCM268 integrates transform-
er-balanced XLR inputs, a switchable microphone/line level transform-
er-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
•
•
•
Built-in 12-volt phantom power
Internal power transformer
Built-in low-cut filter on microphone inputs (below 80 Hz)
Six-segment LED output level meter
FRONT PANEL
1
2
3
4
5
Gain Controls (1-4). Adjusts gain for microphone level
Master Gain Control (MASTER). Adjusts overall output
1
2
3
4
5
inputs and auxiliary level inputs 1-4.
level.
Auxiliary Channel Gain Control (AUX IN). Adjusts the
auxiliary channel input gain.
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.
Output Meter. LED meter indicates peak output signal
level.
REAR PANEL
1
2
3
4
5
6
7
8
Power Connector. Accepts 100-120 Vac (SCM268) or
Auxiliary Level Inputs (AUX LEVEL INPUTS, 1-4). Phono
1
2
5
6
7
8
220-240 Vac (SCM268E).
jacks connect to consumer-level audio sources.
Output Connector (MIC/LINE OUT). Transformer-bal-
anced XLR output connector. Switchable between line and
microphone level.
Auxiliary Input Channel (AUX IN). A dedicated auxil-
iary-level input for the auxiliary channel.
Phantom Power Switch (12V PHANTOM). Recessed
switch turns on phantom power for microphone inputs 1-4.
Output Level Switch (MIC/LINE OUT). Recessed switch
changes the signal level of the XLR output connector:
In = Microphone Level
3
4
Microphone Level Inputs (MIC LEVEL INPUTS). Trans-
former-balanced, microphone-level XLR inputs.
Out = Line Level
Auxiliary Output Connector (AUX OUT). Phono jack
feeds consumer-level audio equipment. Not affected by
MIC/LINE switch.
5
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GAIN CONTROL
INPUT GAIN
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 mi-
crophone input (MIC LEVEL INPUT 1) and the channel 1 auxiliary level
input (AUX LEVEL INPUT 1). The auxiliary gain control knob (AUX IN) af-
fects only the auxiliary input (AUX IN).
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).
Auxiliary Channel
Channel 3
Channel 1
Channel 2
Channel 4
Master Output
GAIN CONTROL
FIGURE 1
OUTPUT LEVEL METER
The six LEDs on the front panel labeled OUTPUT LEVEL METER illumi-
nate 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).
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 clip-
ping.
RED-Clip
GREEN-Nominal
Peak in dBu
PHANTOM POWER
When the phantom power switch on the back panel is on (12V PHAN-
TOM-ON), the SCM268 provides 12 V of phantom power to each XLR mi-
crophone 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.
OFF
ON
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.
Phantom Power Switch
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 lev-
el of the device to which you are connecting the SCM268. The switch is
recessed to prevent accidental engagement.
LINE
MIC
NOTE: The output level switch does not affect the auxiliary output (AUX
OUT) level.
Output Level Switch
6
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CONNECTIONS
The following diagram illustrates a few of the many types of connections
auxiliary level input (AUX LEVEL INPUT 4). Connecting both auxiliary lev-
el and microphone level inputs to a single channel is not recommended
because the SCM268 would not be able to independently mix the two
sources.
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
AUX IN
CHANNEL 4
CHANNEL 3
CHANNEL 2 CHANNEL 1
CONSUMER-LEVEL
EQUIPMENT
CONSUMER-LEVEL
EQUIPMENT
DYNAMIC
MICROPHONE
CONDENSER
MICROPHONE
DYNAMIC
MICROPHONE
CD PLAYER
OR
AM/FM RECEIVER
OR
VCR
TAPE DECK
POWER SUPPLY
OR
OR
AMPLIFIER
70 V P.A.
Â
Â
Â
Â
LOUDSPEAKERS
LINE OUT
AUX OUT
7
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INSTALLATION
SUPPLIED HARDWARE
2. Attach the short rackmount brackets to the outsides of the com-
bined units with eight (8) of the bracket screws.
•
•
4 rubber feet. For stand-alone installation.
1 rackmount bracket, long. For half-rack (single unit) instal-
lations.
•
1 rackmount bracket, short. For half-rack (single) or du-
al-mount 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.
3. After attaching the brackets, mount the unit in an equipment rack
using the supplied rackmount screws and plastic washers.
4 wood screws, 1/2 in. (1.25 cm). For fixed installations.
Bracket Screw
STAND-ALONE INSTALLATION
Wood Screw
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.
Rackmount Screw
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. Attach the rackmount brackets using one of the following
methods:
Single unit (half-rack) installation:
1. Attach the short and long rackmount brackets to the SCM268
with eight (8) of the supplied bracket screws.
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) sup-
plied 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
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INTERNAL MODIFICATIONS
WARNING! Voltages in this equipment are hazardous to life. No user-serviceable parts inside. Refer all servicing to qualified service personnel.
The following table lists the low-cut frequency corners for some of the
most common capacitor values:
DISASSEMBLY
To access the printed circuit board (pc board) for internal modifications,
use the following steps:
Capacitor Value (μF)
Low-Cut Frequency Corner (Hz)
.033
.047
.068
.1
803
564
390
265
120
80
1. Unplug the power cord.
2. Remove the knobs and retainer nuts from the front panel (See
Figure 2).
.22
.33
.47
.68
1.0
2.2
56
39
26.5
12
KNOB ASSEMBLY
PHANTOM POWER DISABLE
FIGURE 2
To disable phantom power for a given microphone input, remove the
specified resistor as listed in the following table:
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
Channel
Remove Resistor:
5. Slide the back panel and pc board out from the rear of the chas-
sis.
1
2
3
4
R15
R25
R35
R45
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.
LINE PAD
To insert a 50 dB line pad for a given microphone input, remove the spec-
ified resistor and short the solder points at the specified pc board loca-
tions. Refer to the following table:
LOW-CUT FILTER
To bypass the built-in low-cut filter for a given channel, remove the spec-
ified resistor and place a 10
location (polarity does not matter). Refer to the following table:
μF to 33μF capacitor in the specified pc board
Channel
Remove Resistors:
R12, R13, R15
R22, R23, R25
R32, R33, R35
R42, R43, R45
Short Solder Points:
X11 and X14
1
2
3
4
Channel
Remove Resistor from:
Place 10μF to 33μF
X21 and X24
Capacitor in:
X31 and X34
1
2
3
4
R18
R28
R38
R48
X17
X27
X37
X47
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.
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 de-
sired corner frequency.
1. Twist together the leads from one side of a 15 kΩ resistor and a
0.1 μF capacitor:
15 KΩ
C = 26.5 ⁄ F
where:
0.1 ΜF
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
Resistor
Insert Resistor-Capacitor
Combination at Jumper
1
2
3
4
R18
R28
R38
R48
X17
X27
X37
X47
9
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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)
Microphone Inputs: 150 Hz to 20 Khz ±2 dB (built-in 80Hz
low-cut)
Auxiliary Inputs: 20 Hz to 20 kHz ±2 dB
Low-Cut Filter (Microphone inputs only)
3dB down at 80 Hz, 6 dB/octave
Polarity
All inputs to all outputs are non-inverting
Overload and Shorting Protection
Shorting outputs, even for prolonged periods, causes no dam-
age. Microphone inputs are not damaged by signals up to +10
dBV; Auxiliary inputs by signals up to +36 dBV
Gain (typical, controls full clockwise)
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
Input
Output
Line
Mic
Aux Out
Low-impedance mic
38 dB
76 dB
65 dB
(150 Ω)
Aux Level
3 dB
40 dB
29 dB
Inputs
Input
Impedance
Designed for
use with
Actual
(typical)
Input
Clipping Level
1.20 Kg (2 lbs, 10 oz)
Mic
19-600 Ω
1.2 kΩ
–5 dBV
Certifications
Aux Level
21 kΩ
>28 dBV
≤2 kΩ
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 perfor-
mance criteria in European Standard EN55103 (1996) parts 1
and 2, for residential (E1) and light industrial (E2) environ-
Outputs
Output
Impedance
Designed for
use with
Actual
(typical)
Output
Clipping Level
ments.
N 108
Mic
Line
low-Z inputs
>600 Ω
0.2 Ω
72 Ω
–21 dBV
+18 dBV
+7 dBV
Replacement Parts
Knob, Master (blue) ............................................... 95B8752
Knob, Channel Gain (white)................................... 95A8752
Line (Power) Cords:
Aux Out
>2 kΩ
870 Ω
Total Harmonic Distortion
SCM268: 100-120 Vac (US/Canada)................ 95A8762
SCM268E: 220-240 Vac (EU)........................... 95A8778
SCM268E (Australia/New Zealand) .................. 95A9128
Fuse, SCM268 (5x20 mm,
<0.25% at +4 dBu output level (through 22 Hz—22 kHz filter;
Input 1 and Master centered, all other controls full counter-
clockwise)
Equivalent Input Hum and Noise(150 Ω source; through 22
250V, 80mA, slow-blow)........................................... 80A730
Fuse, SCM268E (5x20 mm,
Hz—22 kHz filter)
124 dBV
250V, 40mA, slow-blow)............................................80J258
Hardware Kit ........................................................90AF8100
Link Bars (Bracket) ................................................ 53A8443
Single Mount Bracket............................................. 53A8484
Dual Mount Bracket ............................................... 53B8484
Output Hum and Noise (through 22 Hz—22 kHz filter; chan-
nel controls full counterclockwise)
Master full counterclockwise: –92 dBV
Master full clockwise: –70 dBV
Common Mode Rejection
Optional Accessories
>80 dB at 1 kHz
Line (Power) Cord, 230-240 Vac (UK) ................... 95A8713
10
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United States, Canada, Latin America, Caribbean:
5800 W. Touhy Avenue, Niles, IL 60714-4608, U.S.A.
Phone: 847-600-2000 U.S. Fax: 847-600-1212 Intl Fax: 847-600-6446
Europe, Middle East, Africa:
Shure Europe GmbH, Phone: 49-7131-72140 Fax: 49-7131-721414
Asia, Pacific:
Shure Asia Limited, Phone: 852-2893-4290 Fax: 852-2893-4055
미국 , 캐나다 , 중남미 , 카리브해 지역 :
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 美国 传真：847-600-1212 国际 传真：847-600-6446
5800 W. Touhy Avenue, Niles, IL 60714-4608, U.S.A.
전화 : 847-600-2000 미국 팩스 : 847-600-1212 국제 팩스 : 847-600-6446
유럽 , 중동 , 아프리카 :
欧洲、中东、非洲：
Shure Europe GmbH，电话：49-7131-72140 传真：49-7131-721414
Shure Europe GmbH, 전화 : 49-7131-72140 팩스 : 49-7131-721414
아시아 , 태평양 :
亚太地区：
Shure Asia Limited，电话：852-2893-4290 传真：852-2893-4055
Shure Asia Limited, 전화 : 852-2893-4290 팩스 : 852-2893-4055
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