Model SCM810/SCM810E
User Guide
SCM810/SCM810E
EIGHT-CHANNEL MICROPHONE MIXER
©2014 Shure Incorporated
27A21603 (Rev. 01)
Printed in U.S.A.
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DESCRIPTION
The Shure Model SCM810/E is an eight-channel automatic microphone
Each input channel has a two-band equalizer and three logic terminals. The
equalizer reduces unwanted low-frequency audio pickup and makes
different microphone types-lavaliers, boundary and handheld-sound
similar. The logic terminals can be used to control external devices.
mixer designed for use in sound reinforcement, audio recording, and
broadcast applications. The SCM810 dramatically improves audio quality
in any application where multiple microphones are required. Any
low-impedance dynamic or condenser microphone (including wireless) can
be used with the SCM810/E. Multiple SCM810 mixers can be linked to
other SCM810/E mixers, as well as to Shure Models FP410, SCM410 and
SCM800 mixers.
The SCM810 operates on 120 Vac power; the SCM810E operates on 230
Vac power. Each mixer is supplied with a power cord, rack-mounting
hardware, and a link cable.
SYSTEM FEATURES
•
•
Fast-acting, noise-free microphone selection that automatically
adjusts to changes in background room noise
Automatic gain adjustment as additional microphones are
activated
Last Mic Lock-On circuit that maintains ambient sound
Adjustable low-frequency rolloff and high-frequency shelving for
each channel
•
•
Channel activation and clipping indicators
Peak-responding output limiter with selectable thresholds and
LED indicator
Active balanced mic/line inputs and line/level output
Aux-level input with manual level control
Front-panel headphones output with level control
Linking capability for up to 400 microphones
•
•
•
•
•
•
OPERATING PRINCIPLES
The operating concept behind the SCM810/E Automatic Mixer is Shure's
proprietary IntelliMix® circuitry. IntelliMix delivers seamless automatic
mixing by combining three separate functions:
•
•
MaxBus. Controls the number of channels that may be activated
for a single sound source. One talker activates only one channel,
even if multiple microphones “hear” that talker.
Last Mic Lock-On. Keeps the most recently activated micro-
phone open until another microphone is activated. Without Last
Mic Lock-On, a long pause in conversation would cause all micro-
phones to turn off, which would sound as if the audio signal had
been lost. Last Mic Lock-On ensures that background ambience
is always present.
•
Noise Adaptive Threshold. Distinguishes between constant
background noise (such as air conditioning) and changing sound
(such as speech) for each input channel. It continuously adjusts
the activation threshold so that only speech levels louder than the
background noise activate a channel.
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FRONT PANEL FEATURES
MODEL SCM810 FRONT PANEL
FIGURE 1
ᕡ Microphone Channel Gain Controls 1 - 8: Allows adjustment of
microphone gain.
ᕢ Input LED 1 - 8: Lights green when channel is active; lights red at 6
dB below clipping level.
ᕣ Low-Cut Filter 1 - 8: Recessed screwdriver adjustment provides
adjustable low-frequency rolloff (high pass) to reduce undesirable
low-frequency signals.
ᕤ High-Frequency Shelving Filter 1 - 8: Provides level boost or cut in
mid/high-frequency region to compensate for off-axis tone coloration,
or for cutting high-frequency sibilance.
ᕦ Aux INPUT 1/4-inch Phone Jack: Mixes external auxiliary- or
line-level sources into output. This out is not automatic. Signal
appears at output of all linked mixers.
ᕧ MASTER Level Control: Determines the overall mix level.
ᕨ Output Level Meter: Nine-segment LED meter indicates peak output
signal level. Last LED indicates limiter action.
ᕩ PHONES Control and 1/4-inch Phone Jack: Permits monitoring of
mixer output through headphones. The PHONES knob controls head-
phones output level.
µ POWER LED: Lights green when unit is powered.
ᕥ AUX Level Control: Sets the input level for aux-level equipment con-
nected to the adjacent 1/4-inch INPUT phone jack or rear-panel
1/4-inch AUX input.
REAR PANEL FEATURES
¸
ƹ
¹
Ƹ
Ƽ
ƺ
ƽ
ƻ
ƾ
SCM810 REAR PANEL
FIGURE 2
¸ AC Power Connector and Rocker Switch: Connector supplies AC
power to unit when plugged into a power source: the rocker switch
turns the unit on.
ƻ DIRECT OUT 1/4-inch Phone Jacks: Provides non-gated aux-level
signal from each channel. Direct outs are wired pre-fader and pre-EQ.
Can be modified for use as a gated channel output, send/receive
insert point, or external speech gate for mixing consoles (see Internal
Modifications section).
¹ Microphone Logic: DB-25 male connector interfaces with each
channel's GATE OUT, MUTE IN, and OVERRIDE IN logic terminals.
See the Suggested Logic Applications section. NOTE: THIS IS NOT
AN RS-232 PORT.
Ƽ AUX/D.O./D.O. Switch: Located behind the Line Output connector,
this switch selects either aux input function or direct output function for
channel 8 Direct Out jack. Left switch position is AUX IN; center and
right positions are DIRECT OUT.
Ƹ DIP Switch: The 7-position DIP switch provides setup options for the
mixer (see DIP Switches section).
ƽ INPUT 1-8 Removable Block Connectors: Active balanced micro-
ƹ LINK IN/OUT Jacks: Allow multiple mixers to be stacked for addi-
phone- or line-level inputs.
tional inputs. Up to 50 SCM810 mixers can be linked.
ƾ Input 1 - 8 MIC/PHM/LINE Switch: Located behind the removable
block connector, this switch selects operation at either micro-
phone-level (left), microphone-level with 48 V phantom power (cen-
ter), or line-level (right) signals.
ƺ LINE OUTPUT Removable Block Connector: Active balanced
line-level signal for connection to amplifiers, recorders or other mixers.
Output can be modified to microphone level (see Internal
Modifications).
4
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DIP SWITCHES
The rear-panel DIP switch provides the following setup options. The
positions shown in bold type are the factory settings.
NOTE: Switch positions and effects are shown in Figure 3 and also on the
mixer label.
DIP
SWITCH
SW702
(MIXER
REAR
PANEL)
1 2 3 4 5 6 7
MODIFIABLE FUNCTION SWITCHES
FIGURE 3
DIP SWITCH SW702 FUNCTIONS
Switch
Function
Last Mic
Lock-On
Off-Attenuation
Limiter
Threshold
Link
Local/Global
Manual/Auto
Hold Time
Level
Switch Position
1
2
3
4
5,6
7
Number
5 Up
6 Up
= Limiter off
= +8 dBm
5 Down
6 Up
Switch Up
Auto
On
0.4 second
15 dB
Global
5 Up
= +16 dBm
= +4 dBm
6 Down
5 Down
6 Down
Switch Down
Manual
All mics off after
hold time
1.0 second
Local
(completely off)
Manual/Auto: Automatic activation is defeated in the Manual position. In
Manual mode, functions as a standard 8x1 mixer.
Off-Attenuation: Changes the off-attenuation level from 15 dB to infinity
(). With the 15 dB setting, an unused microphone is 15 dB lower in level
than when it is activated. With the setting, an unused microphone is
completely off.
Last Mic Lock-On: Last Mic Lock-On feature keeps the most recently
activated microphone turned on until a newly activated microphone takes
its place. When defeated, microphones turn off after their preset hold time.
Limiter Threshold: Changes the output limiter threshold. Settings are
OFF (factory setting), +16 dBm, +8 dBm, or +4 dBm (see Internal
Modifications for other threshold settings).
Hold Time: Adjusts the time an activated microphone (which is not locked
on) remains on after the talker stops talking. Settings are 0.4 seconds or
1.0 second.
Link Global/Local: Determines whether each linked SCM810 output
contains only its own program output, or that of all linked mixers (see Mixer
Linking for more information).
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INSTALLATION AND SYSTEM SETUP
RACK MOUNTING THE MIXER
To mount the SCM810 in a standard 483 mm (19-inch) audio equipment
rack, slide the mixer into the rack and secure it with the supplied Phillips
head screws, as shown in Figure 4. Use all four screws.
RACK MOUNTING THE SCM810/E
FIGURE 4
SCM810/E CONNECTIONS
Make audio connections as follows (see Figure 5).
TO STEREO OR MONO HEADPHONES
FROM AUX– OR LINE–LEVEL SOURCE
1. Connect microphone- or line-level signal sources to the Channel Input
connectors (use conventional 2-conductor shielded cables).
2. Insert a screwdriver or other tool in the slot above each block connec-
tor and adjust the input slide switch as required: microphone (left posi-
tion), microphone with 48 V phantom power (center position), or line
level (right switch position).
3. Connect the SCM810 Line Level Output to the input of mixers, EQs,
amplifiers or recorders.
4. For headphones monitoring, connect headphones to the front-panel
1/4-inch PHONES jack.
TO AMP/REC/MIXER INPUT (CH. 1–7)
FROM MIC/LINE SOURCE (CH. 1–8)
TO AMP/RECORD/MIXER INPUT
OR FROM AUX SOURCE (CH. 8)
MIXER OUTPUT TO AMP/REC/MIXER INPUT
TO LINKED SCM810 MIXERS
5. Connect the power cord to 120 Vac (SCM810) or 230 Vac
(SCM810E). If the operating voltage is to be changed, refer to the
Internal Modifications section.
TO ADVANCED FUNCTION WIRING
TO 120 VAC POWER SOURCE
AUDIO CONNECTIONS
FIGURE 5
OUTPUT LIMITER SETTINGS
The output limiter prevents distortion during loud program peaks without
affecting normal program levels. This prevents overloading of the devices
connected to the SCM810/E output.
Increasing the individual channel or Master Gain controls will increase the
average output and, in turn, the amount of limiting. As supplied, the
output limiter is defeated. However, you can change the limiter threshold
so that the peak output level is +4, +8, or +16 dBm. Refer to the Internal
Modifications section.
6
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EQUALIZER FUNCTIONS
Low Cut Filter (High-Pass)
+2
0
The low-cut (or high-pass) filter allows all frequencies above its cutoff point
to pass from filter input to filter output without attenuation, while frequencies
below the cutoff are attenuated (see Figure 6). The cutoff point is defined
as the frequency where the signal has dropped 3 dB relative to the flat, or
bandpass, region. Below the cutoff point, the filter exhibits increasingly
more attenuation as the frequency diminishes. The rate at which this
attenuation occurs is defined in decibels per octave (dB/oct). The SCM810
has a one-pole, low-cut (high-pass) filter of 6 dB per octave.
FULL CW
-2
-4
-6
FULL CCW
-8
50%
ROTATION
-10
Low-cut filters are ideally used for attenuating, or rolling off, the audio signal
where extraneous noise, excessive proximity effect, or other unwanted
material is present. For example, the low-frequency vibration cause by
footsteps and vehicle traffic can be transmitted through microphone stands
to the microphone, and then into the sound system. These frequencies,
typically ranging from 5 to 80 Hz, are generally not desirable.
20
100
1,000
FREQUENCY (Hz)
5,000
LOW-CUT FILTER EFFECTS
FIGURE 6
+10
FULL
CW
High-Frequency Shelving
+8
+6
The fixed-frequency equalizer produces a 6 dB boost or cut at 5 kHz and
above (see Figure 7). High-frequency shelving is extremely useful for
boosting flat frequency response, tempering very sibilant vocal
microphones, or enhancing the sound of off-axis lavalier microphones.
+4
+2
0
50%
ROTATE
-2
-4
-6
-8
FULL
CCW
-10
20,000
10,000
200
1,000
FREQUENCY (Hz)
HIGH-FREQUENCY SHELVING EFFECTS
FIGURE 7
USING AN EQUALIZER/FEEDBACK CONTROLLER WITH AN AUTOMATIC MIXER
When setting up a sound system which has an outboard equalizer or
feedback controller in the signal chain, set the SCM810 to MANUAL. This
activates all microphone inputs, so every possible feedback path is open.
With the SCM810 in MANUAL mode, equalize the sound system and/or
“Ring Out” the room to set the feedback controller.
After equalizing the sound system, set the SCM810 to AUTOMATIC mode.
Remember that the input of an automatic mixer drops by 3 dB every time
the number activated inputs doubles. When using an SCM810 in MANUAL
mode, the master output drops by 9 dB when all 8 inputs are activated.
Conversely, it will rise by 9 dB when switched back to AUTOMATIC mode.
BASIC MIXER OPERATION
1. Turn on the Power switch.
2. Adjust each channel level so that its Overload LED flickers only during
very loud speech or noise.
5. If a headphone monitor is to be used, adjust the PHONES control
knob until the desired volume level is reached.The SCM810/E is now
ready to use.
3. Turn unused channel controls full counterclockwise.
4. Adjust the SCM810 Master level control for the required output level,
as indicated by the output peak meter.
NOTE: The SCM810/E mixer is fully automatic. For most applications, no
additional adjustments are required.
7
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NETWORKING MULTIPLE MIXERS
If additional inputs are needed, more SCM810 mixers (as many as 50) can
be “linked” using supplied link cables. Such a configuration can provide up
to 400 microphone inputs.
As long as the link jacks of all mixers are connected (out-to-in, sequentially,
leaving one Link In and one Link Out jack unconnected), the automatic
mixing functions will be shared by all units. All input signals appear at all
linked mixer outputs. There is no master/slave relationship.
To link multiple mixers, connect the LINK OUT of the first mixer to the LINK
IN of the next mixer, and so on (see Figure 8). Leave the LINK IN jack of
the first mixer and the LINK OUT jack of the last mixer unconnected.
The output controls and functions of each linked mixer are post-link and do
not affect the signals appearing at other linked mixer outputs. Each mixer's
Master level control only controls its own output. Each output can be used
independently.
NOTE: The actual off-attenuation in the 15 dB switch position increases as
more mixers are linked. This reduces excessive noise and reverberation
contributed by the increased number of attenuated microphones.
In a linked system, the Aux input of any mixer appears at each linked
mixer's output. See Internal Modifications to defeat the linking of Aux
signals.
IMPORTANT: When using the logic terminals on linked mixers, connect the
LOGIC GROUND terminals of each unit together. Switching clicks may
result if this is not done.
LINKING MIXERS
FIGURE 8
GLOBAL/LOCAL FUNCTIONS
The Global/Local switch selects which input channels appear at that linked
mixer's output. Set to the Global position, all input channels appear at that
mixer's output. Set to the Local position, only its own eight input channels
appear at that mixer's output. The Master level control, in any mode, only
controls the level of its own output.
SCM810 “C” (GLOBAL)
SCM810 “A” (LOCAL)
SCM810 “B” (LOCAL)
RECORDER
The Master level control is independent of the Global/Local switch. The
output level of each mixer is affected only by its own Master control. All
automatic functions (such as Last Mic Lock-on and MaxBus) are connected
on all linked mixers and are not affected by the Global/Local switch.
LINK
An example of the possibilities of this setup is shown in Figure 9 Here two
SCM810s are set to Local, and the resulting sound distribution provides
local sound reinforcement while avoiding feedback. This is a simple
“mix-minus” setup. The third SCM810 is set to Global and feeds a tape
recorder, At the same time, the automatic functions (Last Mic Lock-On,
etc.) remain common to all mixers. The following table summarizes the
mixer settings.
MIXER
Link Global/
Local Switch
Audio Output
Contains...
LOUDSPEAKER
LOUDSPEAKER
A
B
C
Local
Local
A
B
Global
A, B, C
LINKED SCM810 MIXERS
FIGURE 9
LINK CABLES
Additional link cables are available as Shure Part No. 95A1143 (305 mm-12 in.). Longer cables in a variety of lengths are available from Apple Computer
as computer printer connections; they are variously referred to by Apple as “shielded serial cable with two mini DIN-8 connectors,” and “Apple System
Peripheral-8 Cable.”
8
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SPECIFICATIONS
Measurement Conditions (unless otherwise specified): Line voltage 120
Vac, 60 Hz (SCM810) or 230 Vac, 50 Hz (SCM810E); full gain; 1 kHz, one
channel activated; source impedances: Mic 150 , Line 150 ;
terminations: Line 10 k, Phones 300 tip-sleeve and ring-sleeve), Direct
Out 10 k; Auto mode, equalization controls adjusted for flat response
Frequency Response (Ref 1 kHz, channel controls centered)
Input Channel Activation
Attack Time 4 ms
Hold Time0.4 s (Switchable to 1.0 s)
Decay Time0.5 s
Off-Attenuation
15 dB (switchable to )
Overload and Shorting Protection
50 Hz to 20 kHz 2 dB; -3 dB corner at 25 Hz
Voltage Gain (typical, controls full clockwise)
Shorting outputs, even for prolonged periods, causes no damage.
Microphone inputs are not damaged by signals up to 3 V; Line and
Monitor inputs by signals up to 20 V
Output
Equalization
Low-frequency 6 dB/octave cut, adjustable
corner from 25 to 320 Hz
High-frequency6 dB at 5 kHz, 8 dB at
10 kHz, shelving
Line
Headphones Direct Out
Input
Low-impedance
mic (150 )
80 dB
88 dB
34 dB
Limiter
Type Peak
Line
Aux
40 dB
44 dB
20 dB
48 dB
52 dB
28 dB
-6 dB
Threshold Switchable: off, +4, +8, +16
(dBm at output)
-
-
Attack Time 2 ms
Send/Return
Recovery Time 300 ms
Indicator Lights red when limiting occurs
Input LEDs
Inputs
Impedance
Green on channel activation, red at 6 dB below clipping
Phantom Power
Designed for
use with
Actual
(typical)
Input
Clipping
Level
46 Vdc open-circuit through 6.8 k series resistance per DIN 45 596
Operating Voltage
Input
SCM810: 120 Vac rated nominal, 50/60 Hz, 200 mA
SCM810E: 230 Vac rated nominal, 50/60 Hz, 100 mA
Temperature Range
Operating: 0 to 60 C (32 to 140 F)
Storage: -30 to 70 C (-20 to 165 F)
Overall Dimensions
44.5 mm H x 483 mm W x 317 mm D
(1 3/4 x 19 x 12 1/2 inches)
Net Weight
Mic
19-600
2 k
1.6 k
-15 dBV
+22 dBV
Line
10 k
Aux
Send/Return
Outputs
10 k
+22 dBV
+18 dBV
2 k
10 k
2 k
4.3 kg (9 lb 9 oz)
Certifications
Impedance
SCM810: Listed by Underwriters Laboratories, Inc.; cUL Certified
(Canada). SCM810E: Conforms to European Union Directives; Certified to
EN60065; Eligible to bear CE Marking; Conforms to European EMC
Directive 2004/108/EC; Meets Harmonized Standards EN55103-1:1996
and EN55103-2:1996 for residential (E1) and light industrial (E2)
environments.
Designed for
use with
Actual
(typical)
Output
Clipping
Level
Output
Line
>600
60
+18 dBV
+12 dBV
Headphones
8-200 ,
60
recommended
300
Authorized European representative:
Shure Europe GmbH
Headquarters Europe, Middle East & Africa
Department: EMEA Approval
Jakob-Dieffenbacher-Str. 12
75031 Eppingen, Allemagne
Phone: +49-7262-92 49 0
Direct Out
>2 k
1 k
+18 dBV
+18 dBV
Send/Return
>2 k
1 k
Total Harmonic Distortion
Fax: +49-7262-92 49 11 4
<0.1% at +18 dBV output level, 50 Hz to 20 kHz (through 20 Hz-20 kHz
filter; Input 1 and Master at 5, all other controls full counterclockwise)
Hum and Noise
Email: [email protected]
Replacement Parts
Equivalent Input Noise . . . . . . . . . . . . . . . . –125 dBV (150 source;
through 400 Hz –20 kHz filter)
Block Connector ....................................................................... 95A8580
Knob, Master & Phones (white)................................................ 95A8238
Knob, Channel Gain (blue) ....................................................... 95B8238
Line (Power) Cord (SCM810) ..................................................95B8389*
Line (Power) Cord (SCM810E)................................................95C8247*
Link Cable................................................................................. 95B8889
Equivalent Input Hum and Noise:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . –123 dBV (150 source; through
20 Hz - 20 kHz filter)
Output Hum and Noise (through 20 Hz to 20 kHz filter; channel con-
trols full counterclockwise))
Master full counterclockwise . . . . . . . . . . . . . . . . . . . . . . . . . –90 dBV
Master full clockwise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –70 dBV
Common Mode Rejection
>70 dB at 1 kHz
Polarity
Service Statement
For additional service or parts information, please contact the Shure
Service Department at 1-800-516-2525. Outside the United States, please
contact your authorized Shure Service Center.
Mic/Line, Send inputs to all outputs are non-inverting; Aux input to all
outputs is inverting
*For systems requiring other mains connectors, obtain a power cord
with an IEC 320 type mating connector for connection to the SCM810,
and an appropriate plug on the other end for connection to the mains.
The supplied cord uses Harmonized IEC Cordage with color coding
as follows: Brown = Line, Blue = Neutral, Green/Yellow = Ground.
9
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ADVANCED FUNCTIONS
The SCM810's Advanced Functions are recommended only for those who are technically knowledgeable and familiar with audio
electronics.
LOGIC CONNECTION SPECIFICATIONS
The logic functions of the SCM810 expand the mixer's range of installation
and control options. Logic can be used for everything from simple cough
switches to elaborate computer-controlled room systems. (Shure's AMS
Update publication contains additional applications of advanced logic. This
publication is available by contacting Shure's Applications Group.) The
following logic functions are available for each channel:
Logic controls are accessed at the DB-25 multi-pin connector on the rear
panel (Figure 11). The pin connections are given in the following table.
GATE 1
MUTE 1
O’RIDE 2
GATE 3
MUTE 3
O’RIDE 4
GATE 5
MUTE 5
O’RIDE 6
GATE 7
LOGIC
GROUND
MUTE 7
O’RIDE 8
GATE OUT: Follows channel gating and goes to logic “low” (sinks current)
when microphone is gated on. 500 mA of current sinking ability is provided
(see Figure 10A).
+5 V
+5 V
MUTE 2
MUTE 4
GATE 4
O’RIDE 3
MUTE 6
GATE 6
O’RIDE 5
MUTE 8
GATE 8
O’RIDE 7
55K
10K
GATE 2
O’RIDE 1
MUTE IN
OR
OVERRIDE
IN
TO
GATE
OUT
SCM810
LOGIC CONNECTOR
CIRCUIT
FIGURE 11
FROM
SCM810
CIRCUIT
LOGIC CONNECTIONS
Logic Function
Input
Channel
Connector Pin No.
LOGIC
GROUND
GATE OUT1
GATE OUT 2
GATE OUT 3
GATE OUT 4
GATE OUT 5
GATE OUT 6
GATE OUT 7
GATE OUT 8
1
2
3
4
5
6
7
8
1
A
B
15
4
18
7
21
10
24
LOGIC EQUIVALENT CIRCUIT DIAGRAMS
FIGURE 10
MUTE IN: Applying logic “low” (from GATE OUT or a switch closure to logic
ground) gates channel off (see Figure 10B). Channel output drops to -.
OVERRIDE IN: Applying logic “low” (from GATE OUT or a switch closure
to logic ground) forces channel on (see Figure 10B). Factory setting
provides that when both Mute and Override are activated, Mute takes
precedence (see Internal Modifications for Override precedence).
OVERRIDE IN 1
OVERRIDE IN 2
OVERRIDE IN 3
OVERRIDE IN 4
OVERRIDE IN 5
OVERRIDE IN 6
OVERRIDE IN 7
OVERRIDE IN 8
1
2
3
4
5
6
7
8
14
3
17
6
20
9
23
12
LOGIC GROUND: Logic ground is distinct from the SCM810 audio ground.
Make all logic ground connections to this pin, including power supply
ground of external logic circuitry. To avoid switching clicks, do not connect
logic ground to audio, chassis or rack grounds.
MUTE IN 1
MUTE IN 2
MUTE IN 3
MUTE IN 4
MUTE IN 5
MUTE IN 6
MUTE IN 7
MUTE IN 8
1
2
3
4
5
6
7
8
2
16
5
19
8
22
11
25
Logic Ground
all
13
10
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SUGGESTED LOGIC APPLICATIONS
This section contains suggestions on the uses of the SCM810's logic
capabilities. Note that uses of these functions are not limited to the listed
applications. The user is limited only by individual imagination and
creativity. For additional suggestions and solutions to installation problems,
contact Shure's Applications Group.
Remote Channel-On Indicators
Remote indicators can be used to indicate when a talker's microphone is
on. Connect the LEDs and a 5-volt supply to the GATE OUT pins as shown
in Figure 14 (Channels 1, 2 and 3 shown modified). To avoid switching
clicks in the audio output, do not ground the power supply negative terminal
in the audio system or rack ground.
In the following paragraphs, the wiring diagrams refer to the DB-25
connector pins shown in Figure 4.
IMPORTANT: If a single cable is used for the microphone audio signal and
the LED dc power, separate shielded pairs must be used. Failure to carry
the dc power on a shielded pair may result in audible clicking due to
capacitive coupling between the dc power lines and microphone lines.
Cough Button
The talker can turn off his or her microphone during coughing or private
conversations by installing an SPST pushbutton switch between the MUTE
IN and Logic Ground pins for each channel to be modified (see Figure 12-
Channels 1, 2 and 3 modified). When a channel is muted, no audio is
passed. (See “Dead Zone on MUTE IN Defeat” in Internal Modifications
section for more information on MUTE IN logic.)
+
5 V POWER
SUPPLY
–
LOGIC
GROUND
LOGIC
GROUND
G1
G3
M1
M3
G2
R = 470 7, 1/4 W
M2
REMOTE CHANNEL-ON INDICATORS
FIGURE 14
COUGH BUTTONS
Disabling the Gating Function (Bypass)
FIGURE 12
To keep certain microphones on at all times, wire the desired microphone
channel's OVERRIDE IN pins together to the Logic Ground pin. The
selected channels now function as they would in a non-automatic mixer
(see Figure 15-Channels 1, 2 and 3 modified).
Chairperson-Controlled Muting
The chairperson can, by activating a switch, silence all other microphones
and be heard without interruption. For operation in this mode, connect all
the MUTE IN pins together except that of the chairperson's channel, and
wire an SPST pushbutton or toggle switch between those MUTE IN and
Logic Ground pins (see Figure 13-the chairperson is shown as Channel 1).
LOGIC
GROUND
O2
An alternative to a switch is to connect the chairperson's GATE OUT to the
MUTE IN of other channels. When the chairperson's microphone activates,
all other microphones mute.
O1
O3
CH. 1
LOGIC
GROUND
GATING BYPASS
FIGURE 15
M3 M5 M7
M2
M4
M6
CHAIRPERSON-CONTROLLED MUTING
FIGURE 13
11
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Inhibiting Gating for Unwanted Sounds
As described in the Operating Principles section, MaxBus attempts to
activate only one microphone per sound source. Muting a microphone
channel prevents its audio from appearing at the mixer's output. However,
the muted microphone still communicates with other mic channels via
MaxBus. A sound source picked up by a muted microphone will not activate
other microphones.
+
12 V
POWER
SUPPLY
–
Sound sources that may cause unwanted microphone channel activation
include:
•
•
•
•
A noisy fax machine or printer
A squeaky door
A paging system loudspeaker
An audio teleconferencing return signal loudspeaker
LOGIC
GROUND
G3G5
G1
The SCM810 can prevent these and similar sounds from activating
microphones by taking the following steps.
1. Place one microphone near the unwanted sound source. Connect that
microphone's signal to a channel input,
-or-
connect the unwanted sound source directly into a Mic/Line channel
input.
D = 1N4148
2. Mute that channel using the logic terminal (see Figure 16-Channel 1 is
muted).
FROM
POWER
AMP
3. Adjust that channel's gain control just to the level where other
microphones in the system do not activate for the unwanted sound. If
the channel gain is set too high, other system microphones will be
difficult to activate for desired sounds. If set too low, unwanted sounds
will continue to activate other microphones.
LOUDSPEAKER MUTING
FIGURE 17
“Filibuster” Mode
In normal operation, when several people talk, each microphone gates on
so that no speech is missed. In “filibuster” action, a microphone that is
gated on prevents other microphones from gating on. Once a microphone
has gated on, other microphones cannot gate on until the talker has paused
long enough for that microphone to gate off. Thus the person talking has
the floor and cannot be interrupted.
LOGIC
GROUND
M1
To establish this function, first perform the internal Mute to “Inhibit”
modification (see Internal Modifications). Then connect all the MUTE IN
pins of the modified channels together, all the GATE OUT pins of the
modified channels together, and the GATE OUT pin of one modified
channel to the MUTE IN pin of another modified channel (see Figure 18-
Channels 1, 2 and 3 modified). Turn the Last Mic Lock-On switch (SW702,
position 2) to off.
INHIBITING GATING UNWANTED SOUNDS
FIGURE 16
Loudspeaker Muting
Some applications require a loudspeaker to be placed near each talker to
provide audio reinforcement, or to permit telephone conversation or
conference monitoring. Each loudspeaker can cause feedback unless it is
automatically switched off when the talker near it speaks. To provide this
function, connect the GATE OUT terminal of each channel to a separate
loudspeaker muting relay as shown in Figure 17 (Channels 1, 3 and 5
shown modified). Recommended relays are Omron G6B-1174P-US-DC12,
Potter & Brumfield R10-E1Y2-V185, or equivalent (available through
Digi-Key and Newark Electronics).
NOTE: To prevent high-frequency oscillation, do not wire a channel's GATE
OUT pin to its own MUTE IN pin unless the Mute to “Inhibit” change has
been made.
LOGIC
GROUND
G3
G1
M1 M3
JUMPER
NOTE: A diode across each relay coil is required to suppress inductive
voltage spikes which may damage the SCM810.
An existing sound system using 24-volt relays can be used with the
SCM810 without modification if the relay coil current draw is under 500 mA.
G2
M2
“FILIBUSTER” MODE
FIGURE 18
Inhibit Function
See Internal Modifications.
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Mixer logic may be used with 15-volt CMOS logic if a pull-up resistor is
used with each GATE output (see Figure 20-Channel 1 modified).
Diode Isolation of Logic Controls
Two or more control functions using the same logic pins can be isolated
with diodes. In this manner a channel can be muted by an overall group
mute switch, or by its own cough button (see Figure 19-Channels 1, 3 and
5 modified).
+
15 V
5.1 K
POWER
SUPPLY
–
D = 1N4148 OR
EQUIVALENT
GROUP
MUTE
CMOS
LOGIC
GROUND
GATES
M1
M3
M5
LOGIC
GROUND
G1
M1
COUGH
BUTTONS
O1
15-VOLT CMOS
FIGURE 20
DIODE ISOLATION OF LOGIC CONTROLS
FIGURE 19
Digital Controls or Microcomputers
External Logic Devices
The SCM810 logic pins can interface with custom-designed digital control
circuitry or microcomputers for unlimited possibilities of system control
functions.
SCM810 logic levels are directly compatible with TTL and 5-volt CMOS
logic families. For information on logic gate use, refer to the TTL Cookbook
and CMOS Cookbook, both by D. Lancaster, Howard Sams Publishing Co.
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INTERNAL MODIFICATIONS
WARNING: All modifications must be performed by qualified service
2. Where resistors are to be added, through-holes are present on the
technicians.
board.
3. For individual channel modifications, the first number of the reference
designation refers to its channel number, i.e., R1027 refers to a
Channel 1 resistor, X7216 refers to a Channel 7 jumper, etc. All
references to Channels 1 through 8 in the following paragraphs use
Channel 1 jumpers and resistors as reference. Modifications affecting
the Master section are preceded by the number “9" (X901, etc.).
NOTE: Remove AC power before opening the unit.
This section describes SCM810 modifications that can be made using
solder “jumpers” on the printed circuit board; the pads where jumpers may
be used are placed close together so that a single solder drop functions as
a jumper. Note too that:
1. The only printed circuit board legends used for these modifications
are jumpers (X's) and resistors (R's).
To gain access to the main printed circuit board, remove the 8 Phillips head
screws securing the top cover, and remove the top cover. Most
modifications can be made from the top of the main board.
Line-Level Output to Mic-Level Output
Disable Master Level Control
Procedure:
Short jumper X901. Remove resistors R900 and R909.
The Master gain control can be disabled so it cannot be tampered with. The
table indicates the resistor value to be used for the desired gain.
Procedure:
Remove resistor R9230. Install new resistor at jumper X914.
Master Section Gain
Resistance
5.1 k
-6 dB
0
10 k
6 dB
20 k
Change Limiter Threshold
All three threshold settings (+16, +8 and +4 dBm) can be changed. To shift
the threshold down by 6 dB, resistor R will be 82 k. To shift the limiter
thresholds up by 6 dB, R will be 330 k.
Procedure:
Remove resistors R9177 and R9180. Install new resistor R at jumper X907.
Local Aux Operation
With linked mixers, the Aux input from a modified mixer does not link.
Procedure:
Remove resistor R9024.
Direct Out to Post-Fader
A channel's Direct Out phone jacks can be changed from pre- to post-fader.
Procedure:
Short jumper X106. Remove resistor R1011.
Direct Out to Post-Fader Send/Return (Insert)
Changes a channel's 1/4-inch Direct Out jack to a post-fader insert point.
Send is tip of phone jack; return is ring. Insert jacks are useful for inserting
line-level signal processors into a channel. For instance, a parametric EQ
or compressor/limiter can be inserted into a channel for additional
processing.
Procedure:
Short jumpers X101, X102, X105 and X106. Remove resistors R1011 and
R1020.
Direct Out to Gated Direct Out
This post-fader, post-EQ channel output is gated, but without NOMA. In this
mode, if the Local/Global switch is in “Local”, a manual mix of channel
inputs is present at the Line output. The Off-Attenuation level of the Gated
Direct Out signal is infinite.
Procedure:
Short jumpers X104 and X906 (in Master section). Remove resistor R1011.
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SCM810 Speech Gate for Mixing Console
The SCM810 can be used in conjunction with large mixing consoles to
provide automatic mixing for talk shows, panel discussions, and news
shows. Large consoles have channel insert jacks so that external signal
processing devices can be patched into individual channel signal paths.
With this modification the SCM810 can be placed into unbalanced insert
jacks, and the SCM810 used as a high-quality, external, 8-channel speech
gate. This arrangement allows the operator complete control of each
channel via the console's input control strip, while the SCM810 keeps the
number of open microphones to a minimum.
Procedure:
Short jumpers X103, X107, X108 and X906 (in the Master section).
Remove resistors R1011, R1019, and R1020.
In this operational mode:
1. The Direct Out jack tip is the input from the mixing console, and the
ring is the output to the mixing console.
2. The SCM810 channel inputs, faders and EQ do not function.
3. NOMA does not function, channel Off-Attenuation is infinite.
4. The front-panel channel overload indicators indicate gating and
overload for each input.
5. The “Local” operating mode provides a non-automatic audio signal at
the output for use in external mixes.
6. If the insert point on the mixing console is pre-fader, the gain trims
should be set such that all microphone levels are similar.
MUTE IN Precedence to OVERRIDE IN Precedence
With this modification and when both MUTE IN and OVERRIDE IN logic are
grounded for a channel, the Override mode will take precedence (as
supplied, the MUTE IN takes precedence over OVERRIDE IN).
Procedure:
Short jumper X114. Remove resistor R1046.
Dead Zone on MUTE IN Defeat
As supplied, MUTE IN is intended for use as a momentary cough button or
privacy function (mute when necessary). However, if the MUTE IN is
intended to be used so that the talker must unmute microphones to enable
speech pickup (unmute when needed), this modification is needed. This
removes the muted channel from the MaxBus which eliminates “dead
zones.” A dead zone is an area in which a microphone picks up a talker
through a muted microphone and other microphones do not activate for
that talker.
Procedure:
Short jumper X115.
Change MUTE IN to Inhibit
As supplied, a channel will mute when its MUTE IN terminal is grounded.
The mute function can be changed to “Inhibit” by an internal modification
for each channel. After the modification, a logic “Low” at the MUTE IN
terminal prevents that channel from gating on if it is off, but allows it to
remain on if it is already on.
Procedure:
Short jumper X111.
IMPORTANT: To prevent high-frequency oscillation, never connect a
channel's GATE OUT to its own MUTE IN unless the “Inhibit” modification
has been made.
Change OVERRIDE IN to MUTE IN for Use with Filibuster Mode
This modification should only be performed with the Change MUTE IN to
Procedure:
Inhibit modification described above.
Short jumper X113. Remove resistors R1046 and R1058.
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Change Off-Attenuation Level
This modification changes the off-attenuation level from -15 dB to a
selected value. Select from the following resistor values.
Procedure:
Remove resistors R9088 and R9145. Install new resistor at jumper points
X904 and X908.
Off-Attenuation Level
Resistor Value
18 k
10 dB
20 dB
30 dB
50 k
150 k
Increase Hold Time
In addition to the dip switch SW702 options of 0.4- and 1.0-second hold
time, the hold time can be increased to 1.5 seconds. (More than 1.5
seconds is not recommended.)
Procedure:
Install a 470 k resistor across jumper points X902. Move DIP switch down
to 1.0-second position.
Decrease Hold Time
The hold time can be decreased from the factory preset of 0.4 seconds to
0.3 seconds. (Less than 0.3 seconds is not recommended.)
Procedure:
Install a 2 M resistor at jumpers X903.
Remote Control of Link Global/Local, Off-Attenuation, Last Mic Lock-on,
and Automatic/Manual DIP Switches
If desired, these functions can each be remotely controlled with an SPST
switch.
Procedure:
1. Solder a wire in the pc board jumper hole adjacent to the desired
function (printed on the printed circuit board). These jumpers are
located just behind DIP switch SW902.
2. Solder a wire in the pc board jumper hole marked “GND” near switch
SW902.
3. Set the desired DIP switch(es) to the Up position.
4. Run the jumper wires to the desired remote location and solder them
to an SPST toggle switch. The wires can exit the SCM810 chassis
above the DIP switches. Shorting any wire to the Ground wire will set
the function(s) to the corresponding switch “down” position.
United States, Canada,
Latin America, Caribbean:
Shure Incorporated
5800 West Touhy Avenue
Niles, IL 60714-4608 USA
Europe, Middle East, Africa:
Shure Europe GmbH
Jakob-Dieffenbacher-Str. 12,
75031 Eppingen, Germany
Asia, Pacific:
Shure Asia Limited
22/F, 625 King’s Road
North Point, Island East
Hong Kong
Phone: +49-7262-92490
Fax: +49-7262-9249114
Email: [email protected]
Phone: +1 847-600-2000
Fax: +1 847-600-1212 (USA)
Fax: +1 847-600-6446
Email: [email protected]
Phone: +852-2893-4290
Fax: +852-2893-4055
Email: [email protected]
©201ꢀ Shure Incorporated
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