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The Shure Model SCM800 is a full-featured, eight-channel mi- crophone mixer for sound reinforcement, general audio re- cording, and audio-visual systems. Any low-impedance, bal- anced dynamic or condenser microphone, including a wire- less microphone system, can be used with the SCM800 mixer.

Each SCM800 accepts up to eight microphone- or line???level inputs and one aux-level input (two input jacks feed the same channel). Up to four SCM800 mixers can be linked to provide up to 32 input channels. Each input channel has a two-band equalizer, switchable microphone- or line-level operation,

switchable 48 V phantom power, and a 1/4-inch send/receive insert jack.

The SCM800 operates on 120 Vac power; the SCM800E oper- ates 230 Vac power. Both models are supplied with rack- mounting hardware, link cable and removable block terminal connectors. An accessory rack panel adapter (Model RKC800, available separately) converts the removable block input and output connectors to XLR connectors, and the Aux connectors to phono jacks.

FEATURES

SCompatible with Shure SCM810 and FP410 automatic mi- crophone mixers

SAdjustable EQ per channel: low-frequency rolloff and high- frequency shelving

S48 V phantom power selectable for each input

SActive balanced microphone- and line-level inputs and line- level output

SHighly RF-resistant chassis and circuitry

SLED indication of channel clipping

SCM800 FRONT PANEL

SLinking capability for systems up to 32 microphones

STwo Aux-level input jacks that feed one channel

SInsert jack on each channel

SManual mixing of input channels

SInternal Modification permits 230 V operation (SCM800) or 120 V operation (SCM800E)

SFront-panel headphones output with level control

SPeak-responding output limiter with selectable thresholds and LED indicator

1.Microphone Channel Gain Controls 1 - 8: Allows ad- justment of microphone gain.

2.Input LED 1 - 8: Lights red at 6 dB below clipping level.

3.Low-Cut Filter 1 - 8: Recessed screwdriver adjustment provides adjustable low-frequency rolloff (high pass) to reduce undesirable low-frequency signals.

4.High-Frequency Shelving Filter 1 - 8: Recessed screw- driver adjustment provides level boost or cut in mid/high- frequency region for compensation of off-axis lavalier mi- crophones, or for cutting the high-frequency sibilance of vocal microphones.

5.AUX Level Control: Sets the input level for aux-level equipment connected to the adjacent 1/4-inch phone jack INPUT or rear-panel 1/4-inch AUX input.

6.AUX INPUT 1/4-inch Phone Jack: Mixes external auxil- iary- or line-level sources, i.e., tape recorders, into output. 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 monitoring of mixer output through headphones. PHONES control determines headphones output level.

10.POWER LED: Lights green when unit is powered.

11.SCM800: 120 VAC Power Connector and Rocker

Switch: Switch turns unit on when power cord is plugged into 120 Vac. Can be internally changed to 230 V opera- tion (see Voltage Selection).

SCM800E: 230 VAC Power Connector and Rocker

Switch: Switch turns unit on when power cord is plugged into 230 Vac. Can be internally changed to 120 V opera- tion (see Voltage Selection).

12.DIP Switch: The 7-position DIP switch provides control of the output limiter threshold (see DIP Switches).

13.LINK IN/OUT Jacks: Permit multiple SCM800 mixers to be stacked for additional inputs.

14.LINE OUTPUT Removable Block Connector: Active balanced line-level signal for connection to amplifiers, re- corders or other mixers. If necessary, output level can be changed to microphone level. Refer to the Internal Modifi- cations section of this manual.

15.SEND/RECEIVE 1/4-inch Insert Jacks: Post-fader, post-EQ insert point to add external compressor/limiter, graphic or parametric EQ, or other signal processors. Tip is send, ring is return. Can be modified for use as a Direct Out (see Internal Modifications).

16.AUX/INS/INS 3-Position Slide Switch: Selects either aux input function or insert function for channel 8 (only) In- sert jack. Left switch position is AUX IN; center and right positions are INSERT. This switch is located behind Line Output connector.

17.INPUT 1-8 Removable Block Connectors: Active bal- anced microphone- or line-level inputs.

18.Input 1 - 8 MIC/PHM/LINE 3-Position Slide Switch: Se- lects operation at either microphone-level (left), micro- phone-level with 48 V phantom power (center), or line-lev- el (right) signals. This switch is located behind the remov- able block connector.

SCM800/E CONNECTIONS

Refer to Figure 5 and proceed as follows:

1.Connect microphone- or line-level signal sources to the Channel Input connectors (use conventional two-conduc- tor shielded cables).

2.Insert a screwdriver or similar tool into the slot above each block connector and adjust the input slide switch as re- quired: microphone level (left position), 48 V phantom power (center position), or line level (right switch posi- tion).

3.Connect the Line Level Output of the SCM800/E to the input of other mixers, equalizers, amplifiers, or recorders. If multiple SCM800/E mixers are to be used, refer to the Mixer Linking paragraph of this manual.

4.If headphone monitors are to be used, plug them into the1/4-inch PHONES jack on the front-panel.

5.Connect the power cord to a 120 Vac (SCM800) or 230 Vac (SCM800E) power source.

NOTE: For instructions on how to change the operating volt- age of either model, refer to the Internal Modifications section of this manual.

TO STEREO OR MONO HEADPHONES

FROM AUX??? OR LINE???LEVEL SOURCE

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 SCM800 MIXERS

TO POWER SOURCE

SCM800/E AUDIO CONNECTIONS

FIGURE 5

OUTPUT LIMITER THRESHOLD SETTINGS

The DIP switches on the rear-panel, shown below in Figure 3, control the output limiter threshold settings. Switches 5 and 6 change the output limiter threshold to OFF (default setting), +16 dBm, +8 dBm, or +4 dBm. Other settings are as shown in the table at right. Refer to the Internal Modifications section of this manual for additional settings.

NOTE: Switches 1, 2, 3, 4 and 7 are inactive and are not used.

OUTPUT LIMITER THRESHOLD DIP SWITCH

FIGURE 3

DIP SWITCH FUNCTIONS

LINKING MULTIPLE SCM800 MIXERS

Up to four SCM800 mixers can be ???linked??? using the supplied link cables If additional inputs are needed. Such a configura- tion can provide 32 mic inputs. Refer to Figure 6.

When multiple SCM800 mixers are linked, all input signals ap- pear at all linked mixer outputs??????there is no master-slave rela- tionship. The output controls and functions of each linked mix- er 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 independent- ly. In a linked system, the Aux input of any mixer appears at each linked mixer???s output. See Internal Modifications to de- feat the linking of Aux signals.

Link jacks should be connected sequentially: the LINK OUT of one mixer to the LINK IN of the next, leaving one LINK OUT and one LINK IN unconnected.

NOTE: Each doubling of the number of linked mixers de- creases the master output level by 6 dB.

LINKING MULTIPLE SCM800/E MIXERS

FIGURE 6

USING AN SCM800 AS A SUBMIXER

The master output of the SCM800 (or the output of a mixer in a group of linked SCM800 mixers) can be connected to a chan- nel input or the aux input of an automatic mixer, or other types of mixers. See Figure 8.

SCM800

OUT IN

SCM800

MIC IN

1.Turn on the Power switch.

2.Adjust each channel level so that its Overload LED flick- ers only during very loud speech or noise.

3.Turn unused channel controls full counterclockwise.

4.Adjust the Low-Cut and High-Frequency controls adja- cent to each Input Gain control until all microphones sound alike.

5.Adjust the SCM800 Master level control for the desired output level, as indicated by the output peak meter.

6.Adjust the headphones volume level with the PHONES control knob.

LIMITER

The SCM800???s output limiter prevents distortion during loud program peaks without affecting normal program levels. In- creasing the individual or Master level controls will increase the average output and, in turn, the amount of limiting. The lim- iter prevents excessive overloading of devices connected to the SCM800 output. As supplied, the limiter is defeated.

The limiter threshold can be set for a peak output level of +4, +8, or +16 dBm. With the threshold set at +16 dBm, the mixer has 12 dB of headroom at a nominal level of +4 dBm. Refer to the Internal Modifications section for information on how to change the limiter???s settings.

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 at- tenuation, while frequencies below the cutoff are attenuated (see Figure 9). The cutoff point is defined as the frequency where the signal has dropped 3 dB relative to the flat, or band- pass, region. Below the cutoff point, the filter exhibits increas- ingly more attenuation as the frequency diminishes. The rate at which this attenuation occurs is defined in decibels per oc- tave (dB/oct). The SCM800 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 ef- fect, 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 micro- phone, and then into the sound system. These frequencies, typically ranging from 5 to 80 Hz, are generally not desirable.

LOW???CUT FILTER EFFECTS

FIGURE 9

High-Frequency Shelving

The fixed-frequency equalizer produces a 6 dB boost or cut at 5 kHz and above (see Figure 10). High-frequency shelving is extremely useful for boosting flat frequency response, temper- ing very sibilant vocal microphones, or enhancing the sound of off-axis lavalier microphones.

+6

+4

+2

-2

HIGH-FREQUENCY SHELVING EFFECTS

FIGURE 10

Measurement Conditions (unless otherwise specified):

Line voltage 120 Vac, 60 Hz (SCM800) or 230 Vac, 50 Hz (SCM800E); full gain; 1 kHz.

Source impedances: Mic 150 :, Line 150 :

Terminations: Line 10 k:, Phones 300 :tip-sleeve and ring- sleeve), Direct Out 10 k:

Equalization controls adjusted for flat response, Channel 1 gain control full clockwise, other gain controls full counter- clockwise

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)

Inputs

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 : source; through 400 Hz???20 kHz filter)

Equivalent Input Hum and Noise: -123 dBV (150 : source; through 20 Hz - 20 kHz filter)

Output Hum and Noise (through 20 Hz to 20 kHz filter; channel controls full counterclockwise):

Master full counterclockwise: -90 dBV

Master full clockwise: -62 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

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 Time: 2 ms

Recovery Time: 300 ms

Indicator: Lights red when limiting occurs

Input LEDs

Light at 6 dB below clipping

Phantom Power

46 Vdc open-circuit through 6.8 k: series resistance per DIN 45 596

Operating Voltage

SCM800: 120 Vac rated nominal (see Voltage Selection for 230 Vac operation), 50/60 Hz, 200 mA

SCM800E: 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 (-22?? to 158??F)

Overall Dimensions

44.5 mm H x 483 mm W x 317 mm D (13/4 x 19 x 121/2 in.)

Net Weight

4.3 kg (9 lb 9 oz)

Certifications

SCM800: Listed by Underwriters Laboratories, Inc.; listed as Certified by Canadian Standards Association

SCM800E: Conforms to European Union directives; eligible to bear CE marking; VDE GS-Certified to EN 60950; EU EMC Immunity Requirements: EN50082-1

Replacement Parts

Knob, Channel Gain & Phones (white) . . . . . . . 95A8238

Knob, Master (blue) . . . . . . . . . . . . . . . . . . . . . . . . 95B8238

Line (Power) Cord (SCM800) . . . . . . . . . . . . . . 95A8389*

Line (Power) Cord (SCM800E) . . . . . . . . . . . . . 95A8247*

Link Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95A8889

Three -Terminal Block Connector . . . . . . . . . . . . 95A8580

Service Statement

For additional service or parts information, please contact the Shure Service Department at 1-800-516-2525. Outside the United States, please contact your authorized Shure Service Center.

*For systems requiring other mains connectors, use a power cord with an IEC 320 type mating connector for connection to the SCM800, and an appropriate plug on the other end for connection to the mains. The supplied cord uses Harmonized IEC Cordage with color coding as fol- lows: Brown = Line, Blue = Neutral, Green/Yellow = Ground.

WARNING: All modifications must be performed by quali- fied service technicians. Voltages in this equipment are haz- ardous to life. No user-serviceable parts inside. Refer all servicing to qualified service personnel. The safety certifica- tions of the SCM800 do not apply when the operating volt- age is changed from the factory setting.

ABOUT PRINTED CIRCUIT BOARD MODIFICATIONS

SA jumper is represented by ???X??? on the printed circuit board legend, a resistor is represented by an ???R.???

SThe first number in the reference designator indicates the channel number; i.e., R1027 refers to a Channel 1 resistor, and X7216 refers to a Channel 7 jumper, etc.

SComponents in the Master section are preceded by the number ???9??? (X901, etc.).

SThe circuit board contains holes where resistors are to be added.

SA single drop of solder can serve as a jumper between adjacent jumper pads.

SAll Channel modifications in this section use Channel 1 as an example.

The SCM800 can be internally modified to operate on 230 Vac, 50/60 Hz power.

NOTE: The supplied cord uses Harmonized IEC Cordage with

the following color coding: Brown = Line, Blue = Neutral, Green/Yellow = Ground. For systems requiring other mains connectors, obtain a power cord with an IEC 320 type mating connector for connection to the SCM800, and an appropriate plug on the other end for connection to the mains.

ment end and a CEE 7/7 (???Schuko???) mains connector on the other.

The SCM800E can be internally modified to operate on 120 Vac, 50/60 Hz power.

NOTE: The supplied cord uses Harmonized IEC Cordage with

the following color coding: Brown = Line, Blue = Neutral, Green/Yellow = Ground. For systems requiring other mains connectors, obtain a power cord with an IEC 320 type mating connector for connection to the SCM800E, and an appropriate plug on the other end for connection to the mains.

Each channel???s microphone preamplifier gain can be reduced by 15 dB. This may be desirable with extremely high-output mi- crophones.

Procedure:

To pad the gain of the MIC position

1.Remove surface mount resistor R1023.

2.Solder a 680 : resistor at jumper X112. For a greater gain

reduction, use a resistor with a value greater than 680 :. Use a lesser value resistor for less reduction.

To pad the gain of the PHM (phantom) position:

1.Remove surface mount resistor R1026.

2.Solder a 1.5 k: resistor at jumper X110. This reduces gain by 8 dB. For a greater gain reduction, use a resistor with a value greater than 1.5 k:. Use a lesser value resis- tor for less reduction.

NOTE To compensate for higher output condenser micro- phones, the factory set gain in the PHM position is 13 dB lower than the gain in the MIC position.

DISABLE MASTER LEVEL CONTROL

The Master gain control can be disabled so it cannot be tam- pered with. The following table indicates the resistor value to be used for the desired gain.

Procedure:

1.Remove resistor R9230.

2.Install new resistor at jumper X914.

CHANGE LIMITER THRESHOLD

All three threshold settings (+16, +8 and +4 dBm) can be changed. To shift the threshold down by 6 dB, resistor R will be 82 k:. To shift the limiter thresholds up by 6 dB, R will be 330 k:.

Procedure:

1.Remove resistors R9177 and R9180.

2.Install new resistor R at jumper X907.

SEND/RETURN TO DIRECT OUT POST-FADER

A channel???s Insert phone jack can be changed to Direct Out, post-fader.

Procedure:

1.Remove resistors at X101, X102 and X105.

2.Short jumpers at R1020.

REMOTE VOLUME CONTROL OF CHANNELS

The channel, aux, or master levels can be controlled remotely by a dc voltage via an external VCA (Voltage Controlled Ampli- fier). An example of an external VCA is the ST-VCA1 from Ra- dio Design Labs (1???800???281???2683 or www.rdlnet.com).

Procedure:

For channel control:

1.Connect the tip of a 1/4-in. connector to the line input of the VCA, and the sleeve to the ground of the VCA.

2.Connect the ring to the line output of the VCA.

3.Plug the 1/4-in. connector to the Insert jack of the SCM800.

4.Set the channel level control should be set to 5.

For Aux In control:

1.Connect the external source to the VCA line input.

2.Connect the VCA line output to the tip and sleeve of the SCM800 Aux input.

3.Set the Aux control to 5.

For Master control:

1.Connect SCM800 Line output to the VCA line input.

2.Connect the VCA line output to the external device (amplifi- er, tape recorder, etc.).

3.Set Master control to 5.