Shure SCM810 User Manual

SCM810/SCM810AZSCM810/SCM810AZ

EIGHT-CHANNEL MICROPHONE MIXEREIGHT-CHANNEL MICROPHONE MIXER

User Guide

©2006, Shure Incorporated

27A8868 (Rev. 1)

Printed in U.S.A.

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

! IMPORTANT SAFETY INSTRUCTIONS !

1. READ these instructions.

2. KEEP these instructions.

3. HEED all warnings.

4. FOLLOW all instructions.

5. DO NOT use this apparatus near water.

6. CLEAN ONLY with dry cloth.

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

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

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

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

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

WARNING:

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

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

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

12.

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

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

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

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

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

2

DESCRIPTION

The Shure Model SCM810/E is an eight-channel automatic microphone
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, SCM800,
and AMS8100 mixers.

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

OPERATING PRINCIPLES

The operating concept behind the SCM810/E Automatic Mixer is Shure's
patented* IntelliMix

by combining three separate functions:

•

Noise Adaptive Threshold.

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.

®

circuitry. IntelliMix delivers seamless automatic mixing

Distinguishes between constant

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.

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.

• 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

•

MaxBus.

for a single sound source. One talker activates only one channel,
even if multiple microphones “hear” that talker.

•

Last Mic Lock-On.

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 background ambience
is always present.

Controls the number of channels that may be activated

Keeps the most recently activated micro-

3

FRONT PANEL FEATURES









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 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









쐅



 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 head­phones output level.

쐅 POWER LED: Lights green when unit is powered.

쐈

쐉씈

씉

씊씋씌씍

SCM810 REAR PANEL

FIGURE 2

쐈 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.

쐉 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.

씈 DIP Switch: The 7-position DIP switch provides setup options for the

mixer (see DIP Switches section).

씉 LINK IN/OUT Jacks: Allow multiple mixers to be stacked for addi-

tional inputs. Up to 50 SCM810 mixers can be linked.

씊 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).

씎

씋 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).

씌 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.

씍 INPUT 1–8 Removable Block Connectors: Active balanced micro-

phone- or line-level inputs.

씎 Input 1–8 MIC/PHM/LINE Switch: Located behind the removable

block connector, this switch selects operation at either micro­phone-level (left), microphone-level with 48 V phantom power (cen­ter), or line-level (right) signals.

4

DIP SWITCHES

The rear-panel DIP switch provides the following setup options. The posi­tions shown in bold type are the factory settings.

(MIXER

REAR

PANEL)

1 2 3 4 5 6 7

MODIFIABLE FUNCTION SWITCHES

FIGURE 3

DIP SWITCH SW702 FUNCTIONS

Switch

Function

Switch Position

Number→

Switch Up Auto On 0.4 second 15 dB

Manual/Auto

1 2 3 4 5,6 7

Last Mic
Lock-On

Hold Time

NOTE: Switch positions and effects are shown in Figure 3 and also on the

mixer label.

DIP

SWITCH

SW702

Off-Attenuation

Level

Limiter

Threshold

5 Up
= Limiter off
6 Up

5 Down
= +8 dBm
6 Up

5 Up
= +16 dBm
6 Down

Link

Local/Global

Global

Switch Down Manual All mics off after

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 recently ac-

tivated microphone turned on until a newly activated microphone 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.

hold time

1.0 second

5 Down
= +4 dBm
6 Down

∞ (completely off)

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. Settings are
OFF (factory setting), +16 dBm, +8 dBm, or +4 dBm (see Internal Modifica-
tions 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).

Local

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.

SCM810/E CONNECTIONS

Make audio connections as follows (see Figure 5).

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 connec­tor and adjust the input slide switch as required: microphone (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.

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.

RACK MOUNTING THE SCM810/E

TO STEREO OR MONO HEADPHONES

FROM AUX– OR LINE–LEVEL SOURCE

FIGURE 4

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

TO ADVANCED FUNCTION WIRING

TO 120 VAC POWER SOURCE

AUDIO CONNECTIONS

FIGURE 5

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

-10

-8

-6

-4

-2

0

+2

20 100 1,000 5,000

FREQUENCY (Hz)

FULL CW

FULL CCW

50%

ROTATION

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 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.

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.

High-Frequency Shelving

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.

+10

+8
+6

+4

+2

-2

-4

-6

-8

-10

0

200

LOW-CUT FILTER EFFECTS

FIGURE 6

1,000 10,000

HIGH-FREQUENCY SHELVING EFFECTS

FREQUENCY (Hz)

FIGURE 7

20,000

FULL

CW

50%

ROTATE

FULL
CCW

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.

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 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.

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 applications, no
additional adjustments are required.

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.

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.

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.

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 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.

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.

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.

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.

LINK

SCM810 “C” (GLOBAL)

SCM810 “A” (LOCAL)

SCM810 “B” (LOCAL)

RECORDER

MIXER Link Global/

Local Switch

Audio Output

Contains...

A Local A

B Local B

C Global A, B, C

LINK CABLES

Additional link cables are available as Shure Part No. 95A1143 (305 mm­12 in.). Longer cables in a variety of lengths are available from Apple Com­puter as computer printer

LOUDSPEAKER LOUDSPEAKER

LINKED SCM810 MIXERS

FIGURE 9

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; termina­tions: 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)

Output

Input

Low-impedance

mic (150 Ω)

Line 40 dB 48 dB -6 dB

Aux 44 dB 52 dB -

Send/Return 20 dB 28 dB -

Inputs

Input

Mic 19-600 Ω 1.6 kΩ -15 dBV

Line

Aux

Send/Return

Outputs

Output

Line >600 Ω 60 Ω +18 dBV

Headphones 8-200 Ω,

Direct Out >2 kΩ 1 kΩ +18 dBV

Send/Return >2 kΩ 1 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 Ω source;

Equivalent Input Hum and Noise:

. . . . . . . . . . . . . . . . . . . . . . . . . . . . –123 dBV (150 Ω source; through

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

Line Headphones Direct Out

80 dB 88 dB 34 dB

Impedance

Designed for

use with

≤2 kΩ

≤2 kΩ

≤2 kΩ

Impedance

Designed for

use with

60 Ω

recommended

Actual

(typical)

10 kΩ +22 dBV

10 kΩ +22 dBV

10 kΩ +18 dBV

Actual

(typical)

300 Ω +12 dBV

through 400 Hz –20 kHz filter)

Input

Clipping

Level

Output

Clipping

Level

20 Hz - 20 kHz filter)

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. 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 Time2 ms
Recovery Time300 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 kΩ series 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
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

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).

° to 60° C (32° to 140° F)

∞)

N 108

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 supplied cord uses Harmonized IEC Cordage with color coding
as follows: Brown = Line, Blue = Neutral, Green/Yellow = Ground.

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 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).

+5 V

10K

MUTE IN

OR

OVERRIDE

IN

FROM
SCM810
CIRCUIT

GATE

OUT

LOGIC

GROUND

A B

LOGIC EQUIVALENT CIRCUIT DIAGRAMS

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).

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.

FIGURE 10

+5 V

55K

TO

SCM810

CIRCUIT

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.

MUTE 1

O’RIDE 1

GATE 3

O’RIDE 2

MUTE 2

GATE 2

O’RIDE 3

LOGIC CONNECTOR

GATE 5

MUTE 3

O’RIDE 4

MUTE 4

GATE 4

FIGURE 11

O’RIDE 5

MUTE 5

O’RIDE 6

GATE 6

GATE 7

MUTE 6

MUTE 7

O’RIDE 7

GROUND

O’RIDE 8

MUTE 8

GATE 8

LOGICGATE 1

LOGIC CONNECTIONS

Logic Function Input

Channel

GATE OUT1
GATE OUT 2
GATE OUT 3
GATE OUT 4
GATE OUT 5
GATE OUT 6
GATE OUT 7
GATE OUT 8

OVERRIDE IN 1
OVERRIDE IN 2
OVERRIDE IN 3
OVERRIDE IN 4
OVERRIDE IN 5
OVERRIDE IN 6
OVERRIDE IN 7
OVERRIDE IN 8

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

1
2
3
4
5
6
7
8

1
2
3
4
5
6
7
8

Logic Ground all 13

Connector Pin No.

1

15

4

18

7
21
10
24

14

3
17

6
20

9
23
12

2
16

5
19

8
22
11
25

10

SUGGESTED LOGIC APPLICATIONS

O2

O1 O3

LOGIC

GROUND

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.

In the following paragraphs, the wiring diagrams refer to the DB-25 connec­tor pins shown in Figure 4.

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 12­Channels 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.)

LOGIC

GROUND

M1 M3

M2

COUGH BUTTONS

FIGURE 12

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).

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.

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.

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.

+

5 V POWER

SUPPLY

G1 G3

G2

REMOTE CHANNEL-ON INDICATORS

FIGURE 14

–

R = 470

GROUND

&!

, 1/4 W

LOGIC

Disabling the Gating Function (Bypass)

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).

CH. 1

M3 M5M5 M7

M2 M4 M6

CHAIRPERSON-CONTROLLED MUTING

FIGURE 13

LOGIC

GROUND

11

GATING BYPASS

FIGURE 15

Inhibiting Gating for Unwanted Sounds

+

–

12 V
POWER
SUPPLY

G5G3

G1

LOGIC

GROUND

D = 1N4148

FROM

POWER

AMP

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.

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 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,

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 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.

M1

INHIBITING GATING UNWANTED SOUNDS

-or-

FIGURE 16

LOGIC

GROUND

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: 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.

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.

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.

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

JUMPER

G1 M1G3M3

M2G2

“FILIBUSTER” MODE

FIGURE 18

Inhibit Function

See Internal Modifications.

12

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).

GROUP

MUTE

BUTTONS

COUGH

DIODE ISOLATION OF LOGIC CONTROLS

D = 1N4148 OR

EQUIVALENT

M1 M3 M5

FIGURE 19

LOGIC

GROUND

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).

+

5.1 K

G1 M1

O1

15-VOLT CMOS

FIGURE 20

15 V
POWER
SUPPLY

–

CMOS

GATES

LOGIC

GROUND

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 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.

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 rotor 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. Whitefishes Part

No.

100 mA, 250 V 80C258 218.100

200 mA, 250 V 80BC8196 239.200

Digital Controls or Microcomputers

The SCM810 logic pins can interface with custom-designed digital control
circuitry or microcomputers for unlimited possibilities of system control
functions.

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.*

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.

13

INTERNAL MODIFICATIONS

WARNING: All modifications must be performed by qualified 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. 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.

Line-Level Output to Mic-Level Output

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.

Master Section Gain Resistance

-6 dB 5.1 kΩ

0 10 kΩ

6 dB 20 kΩ

Change Limiter Threshold

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.).

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.

Procedure: Short jumper X901. Remove resistors R900 and R909.

Procedure: Remove resistor R9230. Install new resistor at jumper X914.

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 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.

14

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.

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 jumpers X103, X107, X108 and X906 (in the Master sec­tion). Remove resistors R1011, R1019, and R1020.

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.

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.

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 resistor at
jumper points X904 and X908.

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 sec­onds 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 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.

16

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