Shure Microphone M810E User Manual

Model SCM810/M810E  
User Guide  
SCM810/SCM810E  
EIGHT-CHANNEL MICROPHONE MIXER  
©2005, Shure Incorporated  
27C8504 (Rev. 8)  
Printed in U.S.A.  
 
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 differ-  
ent 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-im-  
pedance 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.  
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 automatically  
adjusts to changes in background room noise  
Automatic gain adjustment as additional microphones are activat-  
ed  
Peak-responding output limiter with selectable thresholds and  
LED indicator  
Active balanced microphone-level XLR inputs and an active bal-  
anced Mic/Line level XLR output  
Last Mic Lock-On circuit that maintains ambient sound  
Adjustable low-frequency rolloff and high-frequency shelving for  
each channel  
Aux-level input with manual level control  
Front-panel headphones output with level control  
Linking capability for up to 400 microphones  
Channel activation and clipping indicators  
OPERATING PRINCIPLES  
The operating concept behind the SCM810/E Automatic Mixer is Shure's  
patented* 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.  
3
 
FRONT PANEL FEATURES  
µ
MODEL SCM810 FRONT PANEL  
FIGURE 1  
Microphone Channel Gain Controls 1 - 8: Allows adjustment of  
microphone gain.  
Input LED 1 - 8: Lights green when channel is active; lights red at 6  
dB below clipping level.  
Low-Cut Filter 1 - 8: Recessed screwdriver adjustment provides  
adjustable low-frequency rolloff (high pass) to reduce undesirable  
low-frequency signals.  
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.  
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.  
MASTER Level Control: Determines the overall mix level.  
Output Level Meter: Nine-segment LED meter indicates peak output  
signal level. Last LED indicates limiter action.  
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.  
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
 
DIP SWITCHES  
The rear-panel DIP switch provides the following setup options. The posi-  
tions 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 com-  
pletely off.  
Last Mic Lock-On: Last Mic Lock-On feature keeps the most recently ac-  
tivated 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 Modifica-  
tions 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 con-  
tains only its own program output, or that of all linked mixers (see Mixer  
Linking for more information).  
5
 
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 af-  
fecting 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 out-  
put 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 Mod-  
ifications section.  
6
 
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 atten-  
uation 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 ma-  
terial is present. For example, the low-frequency vibration cause by foot-  
steps and vehicle traffic can be transmitted through microphone stands to  
the microphone, and then into the sound system. These frequencies, typi-  
cally 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 feed-  
back controller in the signal chain, set the SCM810 to MANUAL. This acti-  
vates 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.  
NOTE: The extreme sensitivity of the IntelliMix circuitry may allow some channel gating due to static discharge or electrical disturbance to the power  
or signal lines. The unit will not be damaged: normal operation will resume after the disturbance ceases.  
7
 
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 mix-  
ing 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.  
REMARQUE  
:
Ces jacks sont conçus pour le jumelage des mélangeurs uniquement et non pas pour les entrées ou sorties audio (se reporter  
à
la figure 5).  
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 mix-  
er'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 re-  
sult 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 out-  
put level of each mixer is affected only by its own Master control. All auto-  
matic 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 Com-  
puter 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
 
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 Ω, Line 150 Ω; termina-  
tions: Line 10 kΩ, Phones 300 Ω (tip-sleeve and ring-sleeve), Direct Out 10  
kΩ; Auto mode, equalization 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)  
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  
Shorting outputs, even for prolonged periods, causes no damage. Mi-  
crophone 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-frequency±6 dB at 5 kHz, ±8 dB at  
10 kHz, shelving  
Line  
Headphones Direct Out  
Input  
Low-impedance  
mic (150 Ω)  
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 Time2 ms  
Send/Return  
Recovery Time300 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 kΩ series resistance per DIN 45 596  
Operating Voltage  
Input  
SCM810: 120 Vac rated nominal (see Voltage Selection for 230 Vac op-  
eration), 50/60 Hz, 200 mA  
Mic  
19-600 Ω  
2 kΩ  
1.6 kΩ  
-15 dBV  
+22 dBV  
SCM810E: 230 Vac rated nominal (see Voltage Selection for 120 Vac  
operation), 50/60 Hz, 100 mA  
Line  
10 kΩ  
Temperature Range  
Aux  
Send/Return  
Outputs  
10 kΩ  
+22 dBV  
+18 dBV  
2 kΩ  
Operating0° to 60° C (32° to 140° F)  
Storage-30° to 70° C (-20° to 165° F)  
Overall Dimensions  
10 kΩ  
2 kΩ  
44.5 mm H x 483 mm W x 317 mm D  
(1 3/4 x 19 x 12 1/2 inches)  
Net Weight  
4.3 kg (9 lb 9 oz)  
Certifications  
Impedance  
Designed for  
use with  
Actual  
(typical)  
Output  
Clipping  
Level  
Output  
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).  
Line  
>600 Ω  
60 Ω  
+18 dBV  
+12 dBV  
Headphones  
8-200 Ω,  
60 Ω  
recommended  
300 Ω  
Replacement Parts  
Direct Out  
>2 kΩ  
1 kΩ  
+18 dBV  
+18 dBV  
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  
Send/Return  
>2 kΩ  
1 kΩ  
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 Ω source;  
through 400 Hz –20 kHz filter)  
*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.  
Equivalent Input Hum and Noise:  
. . . . . . . . . . . . . . . . . . . . . . . . . . . . –123 dBV (150 Ω source; 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 input to all  
outputs is inverting  
9
 
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 fol-  
lowing 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 pro-  
vides that when both Mute and Override are activated, Mute takes prece-  
dence (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  
 
SUGGESTED LOGIC APPLICATIONS  
This section contains suggestions on the uses of the SCM810's logic capa-  
bilities. Note that uses of these functions are not limited to the listed appli-  
cations. 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 connec-  
tor 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 capac-  
itive 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 , 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  
 
Inhibiting Gating for Unwanted Sounds  
As described in the Operating Principles section, MaxBus attempts to acti-  
vate only one microphone per sound source. Muting a microphone channel  
prevents its audio from appearing at the mixer's output. However, the mut-  
ed microphone still communicates with other mic channels via MaxBus. A  
sound source picked up by a muted microphone will not activate other mi-  
crophones.  
+
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 micro-  
phones 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 micro-  
phones 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 gat-  
ed 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” modifi-  
cation (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 volt-  
age 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.  
12  
 
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 log-  
ic families. For information on logic gate use, refer to the TTL Cookbook  
and CMOS Cookbook, both by D. Lancaster, Howard Sams Publishing Co.  
VOLTAGE SELECTION  
The SCM810 can be internally modified to operate from 230 Vac, 50/60 Hz  
power.  
5. Replace the power cord with a cord rated for 230 V operation, i.e., an  
IEC appliance connector on the equipment end and a CEE 7/7  
(“Schuko”) mains connector on the other.*  
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.  
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 supplied cord uses Harmonized IEC Cordage with color coding as  
follows: Brown = Line, Blue = Neutral, Green/Yellow = Ground.  
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 rotor to the 230 V posi-  
tion.  
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.  
Whitefishes Part  
No.  
100 mA, 250 V  
200 mA, 250 V  
80C258  
218.100  
239.200  
80BC8196  
13  
 
INTERNAL MODIFICATIONS  
WARNING: All modifications must be performed by qualified service tech-  
nicians.  
3. For individual channel modifications, the first number of the reference  
designation refers to its channel number, i.e., R1027 refers to a Chan-  
nel 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.).  
This section describes SCM810 modifications that can be made using sol-  
der “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. he only printed circuit board legends used for these modifications are  
jumpers (X's) and resistors (R's).  
2. Where resistors are to be added, through-holes are present on the  
board.  
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 modifica-  
tions 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 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 kΩ  
-6 dB  
0
10 kΩ  
6 dB  
20 kΩ  
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 kΩ. To shift the limiter  
thresholds up by 6 dB, R will be 330 kΩ.  
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 process-  
ing.  
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 in-  
puts 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 re-  
sistor R1011.  
14  
 
SCM810 Speech Gate for Mixing Console  
The SCM810 can be used in conjunction with large mixing consoles to pro-  
vide automatic mixing for talk shows, panel discussions, and news shows.  
Large consoles have channel insert jacks so that external signal process-  
ing 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 sec-  
tion). 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 over-  
load 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 sup-  
plied, 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 in-  
tended to be used so that the talker must unmute microphones to enable  
speech pickup (unmute when needed), this modification is needed. This re-  
moves 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 ter-  
minal 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: Short jumper X113. Remove resistors R1046 and R1058.  
Inhibit modification described above.  
Change Off-Attenuation Level  
This modification changes the off-attenuation level from -15 dB to a select-  
ed 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 kΩ  
10 dB  
20 dB  
30 dB  
50 kΩ  
150 kΩ  
15  
 
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 sec-  
onds is not recommended.)  
Procedure: Install a 470 kΩ 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 MΩ 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 func-  
tion (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.  
SHURE Incorporated http://www.shure.com  
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  
16  
 

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