Shure SCM810 User manual

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SCM810
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SCM810/SCM810E
EIGHT-CHANNEL MICROPHONE MIXER
Model SCM810/SCM810E
User Guide
27C8504 (BJ)
2002, Shure Incorporated Printed in U.S.A.

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TABLE OF CONTENTS
DESCRIPTION 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SYSTEM FEATURES 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
OPERATING PRINCIPLES 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FRONT PANEL FEATURES 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
REAR PANEL FEATURES 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DIP SWITCHES 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
INSTALLATION AND SYSTEM SETUP 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RACK MOUNTING THE MIXER 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SCM810/E CONNECTIONS 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
OUTPUT LIMITER SETTINGS 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
EQUALIZER FUNCTIONS 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
USING AN EQUALIZER/FEEDBACK CONTROLLER WITH AN AUTOMATIC MIXER 7. .
BASIC MIXER OPERATION 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
NETWORKING MULTIPLE MIXERS 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GLOBAL/LOCAL FUNCTIONS 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LINK CABLES 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SPECIFICATIONS 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ADVANCED FUNCTIONS 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LOGIC CONNECTION SPECIFICATIONS 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SUGGESTED LOGIC APPLICATIONS 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VOLTAGE SELECTION 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
INTERNAL MODIFICATIONS 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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.
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 accom-
panying this unit.

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DESCRIPTION
The Shure Model SCM810/E is an eight-channel automatic mi-
crophone mixer designed for use in sound reinforcement, audio
recording, and broadcast applications. The SCM810 dramatical-
ly improves audio quality in any application where multiple micro-
phones 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,
SCM800, and AMS8100 mixers.
Each input channel has a two-band equalizer and three logic ter-
minals. 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.
The SCM810/E operates on 100–120 Vac power; the SCM810E
operates on 220–240 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 automatical-
ly adjusts to changes in background room noise
 Automatic gain adjustment as additional microphones are acti-
vated
 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 microphone-level XLR inputs and an active
balanced Mic/Line level XLR 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 patented* IntelliMixcircuitry. IntelliMix delivers seam-
less automatic mixing by combining three separate functions:
•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.
•MaxBus. Controls the number of channels that may be acti-
vated 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 microphones to turn off, which would sound as if the audio
signal had been lost. Last Mic Lock-On ensures that back-
ground ambience is always present.

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FRONT PANEL FEATURES
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1.Microphone Channel Gain Controls 1 - 8: Allows adjust-
ment of microphone gain.
2.Input LED 1 - 8: Lights green when channel is active; lights red
at 6 dB below clipping level.
3.Low-Cut Filter 1 - 8: Recessed screwdriver adjustment pro-
vides adjustable low-frequency rolloff (high pass) to reduce
undesirable low-frequency signals.
4.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.
5.AUX Level Control: Sets the input level for aux-level equip-
ment connected to the adjacent 1/4-inch INPUT phone jack or
rear-panel 1/4-inch AUX input.
6.Aux INPUT1/4-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.
7.MASTER Level Control: Determines the overall mix level.
8.Output Level Meter: Nine-segment LED meter indicates
peak output signal level. Last LED indicates limiter action.
9.PHONES Control and 1/4-inch Phone Jack: Permits moni-
toring of mixer output through headphones. The PHONES
knob controls headphones output level.
10. POWER LED: Lights green when unit is powered.
REAR PANEL FEATURES
MODEL SCM810 REAR PANEL
FIGURE 2
+
AUX IN
DIRECT OUT
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(SWITCH
AUX/D.O/D.O DIRECT
LINE
OUTPUT
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120VAC 50/60 Hz 200mA
MICROPHONE LOGIC
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MIC/PHM/LINE
SWITCH
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OUT MIC/PHM/LINE
SWITCH
DIRECT
OUT
MIC/PHM/LINE
SWITCH
DIRECT
OUT MIC/PHM/LINE
SWITCH
DIRECT
OUT
MIC/PHM/LINE
SWITCH
DIRECT
OUT MIC/PHM/LINE
SWITCH
DIRECT
OUTMIC/PHM/LINE
SWITCH
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(SWITCH BEHIND
CONNECTOR
MIC
LEVEL
PHANTOM
LINE
LEVEL
MIC/PHM/LINE
SWITCH
MIC/PHM/LINE
SWITCH
11. AC Power Connector and Rocker Switch: Connector sup-
plies AC power to unit when plugged into a power source: the
rocker switch turns the unit on.
12. 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 sec-
tion. NOTE: THIS IS NOT AN RS-232 PORT.
13. DIP Switch: The 7-position DIP switch provides setup op-
tions for the mixer (see DIP Switches section).
14. LINK IN/OUT Jacks: Allow multiple mixers to be stacked for
additional inputs. Up to 50 SCM810 mixers can be linked.
15. LINE OUTPUT Removable Block Connector: Active bal-
anced line-level signal for connection to amplifiers, recorders
or other mixers. Output can be modified to microphone level
(see Internal Modifications).
16. 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).
17. AUX/D.O./D.O. Switch: Located behind the Line Output con-
nector, this switch selects either aux input function or direct out-
put function for channel 8 Direct Out jack. Left switch position is
AUX IN; center and right positions are DIRECT OUT.
18. INPUT 1-8 Removable Block Connectors: Active balanced
microphone- or line-level inputs.
19. Input 1 - 8 MIC/PHM/LINE Switch: Located behind the re-
movable block connector, this switch selects operation at ei-
ther microphone-level (left), microphone-level with 48 V
phantom power (center), or line-level (right) signals.

5
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.
MODIFIABLE FUNCTION SWITCHES
FIGURE 3
1 2 3 4 5 6 7
(MIXER
REAR
PANEL)
DIP
SWITCH
SW702
DIP SWITCH SW702 FUNCTIONS
Switch
Function Manual/Auto Last Mic Lock-On Hold Time Off-Attenuation Level Limiter Threshold Link Local/Global
Switch Position
Number→1 2 3 4 5,6 7
Switch Up Auto On 0.4 second 15 dB
5 Up
= Limiter off
6 Up
5 Down
= +8 dBm
6 Up
5 Up
= +16 dBm
6 Down
5 Down
= +4 dBm
6 Down
Global
Switch Down Manual All mics off after
hold time 1.0 second ∞(completely off) Local
Manual/Auto: Automatic activation is defeated in the Manual
position. In Manual mode, functions as a standard 8x1 mixer.
Last Mic Lock-On: Last Mic Lock-On feature keeps the most re-
cently activated microphone turned on until a newly activated mi-
crophone takes its place. When defeated, microphones turn off
after their preset hold time.
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.
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.
Limiter Threshold: Changes the output limiter threshold. Set-
tings are OFF (factory setting), +16 dBm, +8 dBm, or +4 dBm
(see Internal Modifications for other threshold settings).
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).

6
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.
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RACK MOUNTING THE SCM810/E
FIGURE 4
SCM810/E CONNECTIONS
Make audio connections as follows (see Figure 5).
1.Connect microphone- or line-level signal sources to the Chan-
nel Input connectors (use conventional 2-conductor shielded
cables).
2.Insert a screwdriver or other tool in the slot above each block
connector and adjust the input slide switch as required: micro-
phone (left position), 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.
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. AUDIO CONNECTIONS
TO STEREO OR MONO HEADPHONES
FROM AUX–OR LINE–LEVEL SOURCE
TO AMP/RECORD/MIXER INPUT
TO LINKED SCM810 MIXERS
TOADVANCED FUNCTION WIRING
TO 120 VAC POWER SOURCE
TO AMP/REC/MIXER INPUT (CH. 1–7)
FROM MIC/LINE SOURCE (CH. 1–8)
OR FROM AUX SOURCE (CH. 8)
MIXER OUTPUT TO AMP/REC/MIXER INPUT
FIGURE 5
OUTPUT LIMITER SETTINGS
The output limiter prevents distortion during loud program peaks
without affecting normal program levels. This prevents overload-
ing of the devices connected to the SCM810/E output.
Increasing the individual channel or Master Gain controls will in-
crease 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.

7
EQUALIZER FUNCTIONS
Low Cut Filter (High-Pass)
The low-cut (or high-pass) filter allows all frequencies above its
cutoff point to pass from filter input to filter output without attenua-
tion, while frequencies below thecutoff are attenuated (seeFigure
7). 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 increasinglymore attenuation as
the frequency diminishes. The rate at which this attenuation oc-
curs is defined in decibels per octave (dB/oct). The SCM810 has a
one-pole, low-cut (high-pass) filter of 6 dB per octave.
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-fre-
quency 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.
High-Frequency Shelving
The fixed-frequency equalizer produces a 6 dB boost or cut at 5
kHz and above (see Figure 8). High-frequency shelving is ex-
tremely useful for boosting flat frequency response, tempering
very sibilant vocal microphones, or enhancing the sound of off-
axis lavalier microphones.
LOW-CUT FILTER EFFECTS
FIGURE 7
-10
-8
-6
-4
-2
0
+2
20 100 1,000 5,000
FREQUENCY (Hz)
FULL CW
FULL CCW
50%
ROTATION
HIGH-FREQUENCY SHELVING EFFECTS
FIGURE 8
200
-10
-8
-6
-4
-2
0
+2
+4
+6
+8
+10
1,000 10,000 20,000
FREQUENCY (Hz)
FULL
CW
FULL
CCW
50%
ROTATE
USING AN EQUALIZER/FEEDBACK CONTROLLER WITH AN AUTOMATIC MIXER
When setting up a sound system which has an outboard equaliz-
er or feedback controller in the signal chain, set the SCM810 to
MANUAL. This activates all microphone inputs, so every pos-
sible 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 AUTO-
MATIC 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.
3. Turn unused channel controls full counterclockwise.
4. Adjust the SCM810 Master level control for the required out-
put level, as indicated by the output peak meter.
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.
NOTE: The SCM810/E mixer is fully automatic. For most ap-
plications, no additional adjustments are required.
NOTE: The extreme sensitivity of the IntelliMix circuitry may allow some channel gating due to static discharge or electrical dis-
turbance to the power or signal lines. The unit will not be damaged: normal operation will resume after the disturbance ceases.

8
NETWORKING MULTIPLE MIXERS
If additional inputs are needed, more SCM810 mixers (as many
as 50) can be “linked”using supplied link cables. Such a configu-
ration can provide up to 400 microphone inputs.
To link multipel mixers, connect the LINK OUT of the first mixer to
the LINK IN of the next mixer, and so on (see Figure 6). Leave the
LINK IN jack of the first mixer and the LINK OUT jack of the last
mixer unconnected.
LINKING MIXERS
FIGURE 6
As long as the link jacks of all mixers are connected (out-to-in,
sequentially, leaving one Link In and one Link Out jack uncon-
nected), 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.
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 in-
creases 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.
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.
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.
An example of the possibilities of this setup is shown in Figure 8.
Here two SCM810s are set to Local, and the resulting sound dis-
tribution provides local sound reinforcement while avoiding feed-
back. This is a simple “mix-minus”setup. The third SCM810 is
set to Global and feeds a tape recorder, At the same time, the au-
tomatic 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...
A Local A
B Local B
C Global A, B, C
LINKED SMC810 MIXERS
FIGURE 8
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SCM810 “A”(LOCAL)
SCM810 “B”(LOCAL)
LINK
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SCM810 “C”(GLOBAL) RECORDER
LINK CABLES
Additional link cables are available as Shure Part No. 95A1143
(305 mm—12 in.). Longer cables in a variety of lengths are avail-
able 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.”

9
SPECIFICATIONS
Measurement Conditions (unless otherwise specified): Line volt-
age 120 Vac, 60 Hz (SCM810) or 230 Vac, 50 Hz (SCM810E);
full gain; 1 kHz, one channel activated; source impedances: Mic
150Ω, Line 150 Ω; terminations: Line 10 kΩ, Phones 300 Ω (tip-
sleeve and ring-sleeve), Direct Out 10 kΩ; Auto mode, equaliza-
tion controls adjusted for flat response
Frequency Response (Ref 1 kHz, channel controls centered)
50 Hz to 20 kHz ±2 dB; -3 dB corner at 25 Hz
Voltage Gain (typical, controls full clockwise)
Output
Input Line Head-
phones Direct Out
Low-impedance
mic (150 Ω)80 dB 88 dB 34 dB
Line 40 dB 48 dB –6 dB
Aux 44 dB 52 dB —
Send/Return 20 dB 28 dB —
Inputs
Impedance
Input Designed for use with Actual
(typical) Input Clipping
Level
Mic 19-600 Ω1.6 kΩ-15 dBV
Line ≤2 kΩ10 kΩ+22 dBV
Aux ≤2 kΩ10 kΩ+22 dBV
Send/Return ≤2 kΩ10 kΩ+18 dBV
Outputs
Impedance
Output Designed for use with Actual
(typical) Output Clipping
Level
Line >600 Ω60 Ω+18 dBV
Head-
phones 8-200 Ω, 60 Ωrecom-
mended
300 Ω+12 dBV
Direct Out >2 kΩ1 kΩ+18 dBV
Send/Return >2 kΩ1 kΩ+18 dBV
Total Harmonic Distortion
<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
Equivalent Input Noise -125 dBV (150 Ωsource;. . . . . . . . .
through 400 Hz - 20 kHz filter)
Equivalent Input Hum and Noise . . . . . . . . . . . . . . . . . . . . . . .
-123 dBV (150 Ωsource; through
20 Hz - 20 kHz filter)
Output Hum and Noise (through 20 Hz to 20 kHz filter; channel
controls full counterclockwise))
Master full counterclockwise -90 dBV. . . . . . . . . . . . . . . . .
Master full clockwise -70 dBV. . . . . . . . . . . . . . . . . . . . . . . .
Common Mode Rejection
>70 dB at 1 kHz
Polarity
Mic/Line, Send inputs to all outputs are non-inverting; Aux in-
put to all outputs is inverting
Input Channel Activation
Attack Time 4 ms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hold Time 0.4 s (switchable to 1.0 s). . . . . . . . . . . . .
Decay Time 0.5 s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Off-Attenuation
15 dB (switchable to ∞)
Overload and Shorting Protection
Shorting outputs, even for prolonged periods, causes no dam-
age. Microphone inputs are not damaged by signals up to 3 V;
Line and Monitor inputs by signals up to 20 V
Equalization
Low-frequency 6 dB/octave cut, adjustable. . . . . . . . . . . . . . corner from 25 to 320 Hz
High-frequency ±6 dB at 5 kHz, ±8 dB at. . . . . . . . . . . . . . . . 10 kHz, shelving
Limiter
Type Peak. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Threshold Switchable: off, +4, +8, +16. . . . . . . . . . . . . . . . . . (dBm at output)
Attack Time 2 ms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recovery Time 300 ms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Indicator Lights red when limiting occurs. . . . . . . . . . . . . .
Input LEDs
Green on channel activation, red at 6 dB below clipping
Phantom Power
46 Vdc open-circuit through 6.8 kΩseries resistance per DIN
45 596
Operating Voltage
SCM810: 120 Vac rated nominal (see Voltage Selection for
230 Vac operation), 50/60 Hz, 200 mA
SCM810E: 230 Vac rated nominal (see Voltage Selection
for 120 Vac operation), 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
(13/4x 19 x 121/2inches)
Net Weight
4.3 kg (9 lb 9 oz)
Certifications
SCM810: Listed by Underwriters Laboratories, Inc., listed as
Certified by Canadian Standards Association; SCM810E:
Conforms to European Union directives, eligible to bear CE
marking; VDE GS-Certified to EN 60 950; meets European
Union EMC Immunity Requirements (EN 50 082–1, 1992).
Replacement Parts
Block Connector 95A8580. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Knob, Master & Phones (white) 95A8238. . . . . . . . . . . . . . . .
Knob, Channel Gain (blue) 95B8238. . . . . . . . . . . . . . . . . . .
Line (Power) Cord (SCM810) 95A8389*. . . . . . . . . . . . . . . .
Line (Power) Cord (SCM810E) 95A8247*. . . . . . . . . . . . . . .
Link Cable 95A8889. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
*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 sup-
plied cord uses Harmonized IEC Cordage with color coding as follows:
Brown = Line, Blue = Neutral, Green/Yellow = Ground.

10
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’sAMS Update publication contains addi-
tional applications of advanced logic. This publication is avail-
able by contacting Shure’s Applications Group.) The following
logic functions are available for each channel:
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).
LOGIC EQUIVALENT CIRCUIT DIAGRAMS
FIGURE 10
GATE
OUT
LOGIC
GROUND
FROM
SCM810
TO
SCM810
MUTE IN
OR
OVERRIDE
IN
55K
10K
+5 V +5 V
A B
CIRCUIT
CIRCUIT
MUTE IN: Applying logic “low”(from GATE OUT or a switch clo-
sure to logic ground) gates channel off (see Figure 10B). Chan-
nel output drops to -∞.
OVERRIDE IN: Applying logic “low”(from GATE OUT or a switch
closure to logic ground) forces channel on (see Figure 10B). Fac-
tory setting provides that when both Mute and Override are acti-
vated, Mute takes precedence (see Internal Modifications for
Override precedence).
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.
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.
LOGIC CONNECTOR
FIGURE 11
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ÁÁÁÁÁÁÁÁÁÁÁ
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LOGICGATE 1
MUTE 1
O’RIDE 2
GATE 3
MUTE 3
O’RIDE 4
GATE 5
MUTE 5
O’RIDE 6
GATE 7
MUTE 7
O’RIDE 8
O’RIDE 1
GATE 2
MUTE 2
O’RIDE 3
GATE 4
MUTE 4
O’RIDE 5
GATE 6
MUTE 6
O’RIDE 7
GATE 8
MUTE 8
GROUND
LOGIC CONNECTIONS
Logic Function Input
Channel Connector Pin No.
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
15
4
18
7
21
10
24
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
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

11
SUGGESTED LOGIC APPLICATIONS
This section contains suggestions on the uses of the SCM810’s
logic capabilities. Note that uses of these functions are not limit-
ed to the listed applications. The user is limited only by individual
imagination and creativity. For additional suggestions and solu-
tions to installation problems, contact Shure’s Applications
Group.
In the following paragraphs, the wiring diagrams refer to the
DB-25 connector pins shown in Figure 10.
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 in-
formation on MUTE IN logic.)
COUGH BUTTONS
FIGURE 12
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M1 M3
M2
LOGIC
GROUND
Chairperson-Controlled Muting
The chairperson can, by activating a switch, silence all other mi-
crophones 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).
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.
CHAIRPERSON–CONTROLLED MUTING
FIGURE 13
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CH. 1
M3 M5M5 M7
M2 M4 M6
LOGIC
GROUND
Remote Channel-On Indicators
Remote indicators can be used to indicate when a talker’s micro-
phone 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.
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.
FIGURE 14
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5 V POWER
SUPPLY
+–
R = 470 Ω
REMOTE CHANNEL–ON INDICATORS
G1 G3
G2
LOGIC
GROUND
, 1/4 W
RR
R
Disabling the Gating Function (Bypass)
To keep certain microphones on at all times, wire the desired mi-
crophone 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).
GATING BYPASS
FIGURE 15
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ÁÁÁÁÁÁÁÁ
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O2
O1 O3
LOGIC
GROUND

12
Inhibiting Gating for Unwanted Sounds
As described in the Operating Principles section, MaxBus at-
tempts to activate only one microphone per sound source. Mut-
ing a microphone channel prevents its audio from appearing at
the mixer’s output. However, the muted microphone still commu-
nicates with other mic channels via MaxBus. A sound source
picked up by a muted microphone will not activate other micro-
phones.
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
The SCM810 can prevent these and similar sounds from activat-
ing microphones by taking the following steps.
1.Place one microphone near the unwanted sound source. Con-
nect that microphone’s signal to a channel input,
—or—
connect the unwanted sound source directly into a Mic/Line
channel input.
2.Mute that channel using the logic terminal (see Figure
16—Channel 1 is muted).
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 micro-
phones will be difficult to activate for desired sounds. If set too
low, unwanted sounds will continue to activate other micro-
phones.
INHIBITING GATING FOR UNWANTED SOUNDS
FIGURE 16
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ÁÁÁÁÁÁÁÁ
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M1
LOGIC
GROUND
Loudspeaker Muting
Some applications require a loudspeaker to be placed near each
talker to provide audio reinforcement, or to permit telephone con-
versation 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 modi-
fied). Recommended relays are Omron G6B-1174P-US-DC12,
Potter & Brumfield R10-E1Y2-V185, or equivalent (available
through Digi-Key and Newark Electronics).
NOTE: A diode across each relay coil is required to suppress in-
ductive 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.
LOUDSPEAKER MUTING
FIGURE 17
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ÁÁÁÁÁÁÁÁÁ
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ÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁ
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+
–
12 V
POWER
SUPPLY
G5G3
G1
LOGIC
GROUND
D = 1N4148
FROM
POWER
AMP
DDD
“Filibuster” Mode
In normal operation, when several people talk, each microphone
gates on so that no speech is missed. In “filibuster”action, a mi-
crophone that is gated on prevents other microphones from gat-
ing 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.
To establish this function, first perform the internal Mute to “Inhib-
it”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 modi-
fied channel (see Figure 18—Channels 1, 2 and 3 modified).
Turn the Last Mic Lock-On switch (SW702, position 2) to off.
NOTE: To prevent high-frequency oscillation, do not wire a chan-
nel’s GATE OUT pin to its own MUTE IN pin unless the Mute to
“Inhibit”change has been made.
“FILIBUSTER”MODE
FIGURE 18
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ÁÁÁÁÁÁÁÁÁ
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ÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁ
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JUMPER G1 M1
G3 M3
M2G2
LOGIC
GROUND
Inhibit Function
See Internal Modifications.

13
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 18—Channels 1, 3 and 5 modified).
DIODE ISOLATION OF LOGIC CONTROLS
FIGURE 18
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ÁÁÁÁÁÁÁÁÁ
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ÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁ
Á
Á
GROUP
MUTE
COUGH
D = 1N4148 OR
EQUIVALENT
M1 M3 M5 LOGIC
GROUND
BUTTONS
External Logic Devices
SCM810 logic levels are directly compatible with TTL and 5-volt
CMOS logic families. For information on logic gate use, refer to
theTTL Cookbook and CMOS Cookbook, both by D. Lancaster,
Howard Sams Publishing Co.
Mixer logic may be used with 15-volt CMOS logic if a pull-up re-
sistor is used with each GATE output (see Figure 19—Channel 1
modified).
15–VOLT CMOS
FIGURE 19
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ÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁ
ÁÁ
ÁÁ
ÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁ
Á
Á
15 V
POWER
+
–
SUPPLY
CMOS
GATES
5.1 K
G1 M1
O1
LOGIC
GROUND
Digital Controls or Microcomputers
The SCM810 logic pins can interface with custom-designed digi-
tal control circuitry or microcomputers for unlimited possibilities
of system control functions.
VOLTAGE SELECTION
The SCM810 can be internally modified to operate from 230 Vac,
50/60 Hz power.
WARNING: Voltages in this equipment are hazardous to life.
No user-serviceable parts inside. Refer all servicing to qualified
service personnel. The safety certifications of the SCM810 do
not apply when the operating voltage is changed from the factory
setting.
To change the operating voltage, follow these steps.
1.Disconnect the SCM810 from the AC power source.
2.Remove the eight Phillips head screws securing the top cover.
3.Locate Voltage Selector switch SW903 adjacent to power
transformer T901 and, using a screwdriver, turn the center ro-
tor to the 230 V position.
4.Locate Fuse F901 and remove it. Replace it with a 100 mA,
250 V, time delay fuse for 230-volt operation (200 mA, 250 V,
slow-blow fuse for 120-volt operation).
Fuse part numbers are:
Fuse Type Shure Part No. Littelfuse Part
No.
100 mA, 250 V 80C258 218.100
200 mA, 250 V 80BC8196 239.200
5.Replace the power cord with a cord rated for for 230 V opera-
tion, i.e., an IEC appliance connector on the equipment end and
a CEE 7/7 (“Schuko”) mains connector on the other.*
Similarly, the SCM810E can be internally modified to operate
from 120 Vac, 50/60 Hz power.
*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 sup-
plied cord uses Harmonized IEC Cordage with color coding as follows:
Brown = Line, Blue = Neutral, Green/Yellow = Ground.

14
INTERNAL MODIFICATIONS
WARNING: All modifications must be performed by quali-
fied service technicians.
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 modifi-
cations are jumpers (X’s) and resistors (R’s).
(2) Where resistors are to be added, through-holes are present
on the 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 fol-
lowing paragraphs use Channel 1 jumpers and resistors as
reference. Modifications affecting the Master section are pre-
ceded by the number “9”(X901, etc.).
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 Procedure: Short jumper X901. Remove resistors R900 and
R909.
Disable Master Level Control
The Master gain control can be disabled so it cannot be tam-
pered with. The table indicates the resistor value to be used for
the desired gain.
Master Section Gain Resistance
-6 dB 5.1 kΩ
010 kΩ
6 dB 20 kΩ
Procedure: Remove resistor R9230. Install new resistor at jump-
er X914.
Change Limiter Threshold
All three threshold settings(+16, +8 and +4 dBm)canbechanged.
To shift the threshold down by 6 dB, resistor R will be 82 kΩ. To
shift the limiter thresholds up by 6 dB, R will be 330 kΩ.
Procedure: Remove resistors R9177 and R9180. Install new re-
sistor 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 in-
sert 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 in-
serted 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.

15
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 dis-
cussions, 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.
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.
Procedure: Short jumpers X103, X107, X108 and X906 (in the
Master section). Remove resistors R1011, R1019, and R1020.
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 un-
mute 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 in-
ternal modification for each channel. After the modification, alogic
“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.
IMPORTANT: To prevent high-frequency oscillation, never con-
nect a channel’s GATE OUT to its own MUTE IN unless the “In-
hibit”modification has been made.
Procedure: Short jumper X111.
Change OVERRIDE IN to MUTE IN for Use with Filibuster Mode
This modification should only be performed with the Change
MUTE IN to Inhibit modification described above. Procedure: Short jumper X113. Remove resistors R1046 and R1058.
Change Off-Attenuation Level
This modification changes the off-attenuation level from -15 dB
to a selected value. Select from the following resistor values.
Off-Attenuation Level Resistor Value
10 dB 18 kΩ
20 dB 50 kΩ
30 dB 150 kΩ
Procedure: Remove resistors R9088 and R9145. Install new re-
sistor at jumper points X904 and X908.

16
Increase Hold Time
In addition to the dip switch SW702 options of 0.4- and 1.0-sec-
ond hold time, the hold time can be increased to 1.5 seconds.
(More than 1.5 seconds is not recommended.)
Procedure: Install a 470 kΩresistor 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 recom-
mended.)
Procedure: Install a 2 MΩresistor 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 de-
sired function (printed on the printed circuit board). These
jumpers are located just behind DIP switch SW702.
2.Solder a wire in the pc board jumper hole marked “GND”near
switch SW702.
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.
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