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The Shure Model SCM800 is a full-featured, eight-channel microphone mixer for sound reinforcement, general audio recording, and audio-visual systems. Any low-impedance, balanced dynamic or condenser microphone, including a wireless 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 ¼-inch send/ receive insert jack.
The SCM800 operates on 120 Vac power; the SCM800E operates on 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.
1. Microphone Channel Gain Controls 1 - 8:
Allows adjustment 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 screwdriver adjustment provides level boost or cut in mid/high frequency region for compensation of off-axis lavalier microphones, 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 ¼-inch phone jack INPUT or rearpanel ¼-inch AUX input.
6. AUX INPUT ¼-inch Phone Jack:
Mixes external auxiliary- 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 ¼-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.
SCM800E: 230 VAC Power Connector and Rocker Switch:
Switch turns unit on when power cord is plugged into 230 Vac.
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, recorders or other mixers. If necessary, output level can be changed to microphone level. Refer to the Internal Modifications section of this manual.
15. SEND/RECEIVE ¼-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) Insert 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 balanced microphone- or line-level inputs.
18. Input 1 - 8 MIC/PHM/LINE 3-Position Slide Switch:
Selects operation at either microphone-level (left), microphone-level with 48 V phantom power (center), or line-level (right) signals. This switch is located behind the removable block connector.
Rack mounting the SCM800/E
To mount an SCM800 or SCM800E in a standard 483 mm (19-inch) audio equipment rack so that the front panel faces out, as shown in Figure 4. Then secure the mixer to the rack with the four supplied Phillips head screws.
Refer to Figure 5 and proceed as follows:
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.
|DIP Switch Position||Limiter Threshold|
|5 Up, 6 Up||Limiter Off (default)|
|5 Down, 6 Up||+8 dBm|
|5 Up, 6 Down||+16 dBm|
|5 Down, 6 Down||+4 dBm|
Up to four SCM800 mixers can be “linked” using the supplied link cables If additional inputs are needed. Such a configuration can provide 32 mic inputs. Refer to Figure 6. When multiple SCM800 mixers are linked, 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. 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.
Link jacks should be connected sequentially: theLINK OUTof 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 decreases the master output level by 6 dB.
An SCM800 can be interfaced with Shure SCM810 and FP410 automatic microphone mixers via the link jacks. Linking an SCM800 is equivalent to adding an additional mixer with eight open microphones to a system. Because of the loading effects of additional open microphones, only one SCM800 can be linked to an automatic system. When using more than one SCM800 with other Shure automatic mixers, connect them as described in the following section.
NOTE: When linking an SCM800 to an automatic system, use the SCM800 LINK OUT jack to interface with the LINK IN jack of the automatic system (see Figure 7).
The master output of the SCM800 (or the output of a mixer in a group of linked SCM800 mixers) can be connected to a channel input or the aux input of an automatic mixer, or other types of mixers. See Figure 8.
Additional 381 mm (15 in.) link cables are available as Shure Part No. 95A8889. Longer cables in a variety of lengths are available from Apple Computer as computer printer connections; they are variously referred to by Apple as “shielded serial cable with two mini DIN-8 connectors,” and “Apple System Peripheral–8 Cable.”
The SCM800’s output limiter prevents distortion during loud program peaks without affecting normal program levels. Increasing the individual or Master level controls will increase the average output and, in turn, the amount of limiting. The limiter 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.
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 9). 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 SCM800 has a one-pole, low-cut (highpass) 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.
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, tempering very sibilant vocal microphones, or enhancing the sound of off-axis lavalier microphones.
NOTE: Remove AC power before opening the unit.
Each channel’s microphone preamplifier gain can be reduced by 15 dB. This may be desirable with extremely high-output microphones.
To pad the gain of the MIC position:
To pad the gain of the PHM (phantom) position:
NOTE: To compensate for higher output condenser microphones, the factory-set gain in the PHM position is 13 dB lower than the gain in the MIC position.
The Master gain control can be disabled so it cannot be tampered with. The following table indicates the resistor value to be used for the desired gain.
|Master Section Gain||Resistance|
|-6 dB||5.1 kΩ|
|6 dB||20 kΩ|
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 Rwill be 82 kΩ. To shift the limiter thresholds up by 6 dB, R will be 330 kΩ.
With linked mixers, the Aux input from a modified mixer does not link.
Remove resistor R9024.
Changes a channel’s ¼-inch insert jack to a Direct Out jack.
A channel’s Insert phone jack can be changed to Direct Out, post-fader.
The channel, aux, or master levels can be controlled remotely by a dc voltage via an external VCA (Voltage Controlled Amplifier). An example of an external VCA is the ST-VCA1 from Radio Design Labs (1–800–281–2683 or www.rdlnet.com).
For channel control:
For Aux In control:
For Master control:
(typical, controls full clockwise)
<0.1%at +18 dBVoutput level, 50 Hz to 20 kHz(through 20 Hz-20 kHz filter); Input 1 and Master at 5, all other controls full counterclockwise)
|Equivalent Input Noise||-125 dBV(150 Ω source; through 400 Hz-20 kHz filter)|
|Equivalent Input Hum and Noise||-123 dBV(150 Ω source; through 20 Hz-20 kHz filter)|
|Output Hum and Noise||through 20 Hz-20 kHz filter; channel controls full counterclockwise|
|Master full counterclockwise||-90 dBV|
|Master full clockwise||-62 dBV|
>70 dB at 1 kHz
Mic/Line, Send inputs to all outputs are non-inverting; Aux input to all outputs is inverting
Shorting outputs, even for prolonged periods, causes no damage. Microphone inputs are not damaged by signals up to 3 V; Lines and Monitor inputs by signals up to 20 V
|Low-frequency||6 dB/octavecut, adjustable corner from 25 to 320 Hz|
|High-Frequency||±6dB/octaveat 5 kHz, ± dBat 10 kHz, shelvingat 5|
|Threshold||Switchable: off, +4, +8, +16 ( dBm at output)|
|Indicator||Lights red when limiting occurs|
Light at 6 dBbelow clipping
46 V DC open-circuit through6.8 k Ω series resistance per DIN 45 596
|SCM800||120 V AC rated nominal, 50/60 Hz, 200 mA|
|SCM800E||230 V AC rated nominal, 50/60 Hz, 100 mA|
|Operating Temperature||0° to 60° C (32° to140° F)|
|Storage Temperature||-30° to 70° C (-22° to158° F)|
44.5 mm H x 483 mm W 317 mm D (1¾ x 19 x 12½ in.)
4.3 kg (9 lb ., 9 oz.)
|Input||Impedance||Input Clipping Level|
|Designed for use with||Actual (typical)|
|Mic||19‒600 Ω||10 kΩ||-12 dBV|
|Line||≤2 kΩ||10 kΩ||+22 dBV|
|Aux||≤2 kΩ||10 kΩ||+22 dBV|
|Send/Return||≤2 kΩ||10 kΩ||+18 dBV|
|Output||Impedance||Output Clipping Level|
|Designed for use with||Actual (typical)|
|Line||>600 Ω||60 Ω||-18 dBV|
|Headphone||8‒200 Ω (60 Ω recommended)||300 Ω||+12 dBV|
|Direct Output||>2 kΩ||1 kΩ||+18 dBV|
|Send/Return||>2 kΩ||1 kΩ||+18 dBV|
|Knob, Channel Gain and Phones (white)||95A8238|
|Knob, Master (blue)||95B8752|
|Line (Power) Cord (SCM800)||95B8389|
|230 VAC Power Line Cord||95B8247|
|Three -Terminal Block Connector||95B8580|
For additional service or parts information, please contact Shure's Service department at 1-800-516-2525. Outside the United States, please contact your authorized Shure Service Center.
SCM800: Listed by Underwriters Laboratories, Inc.; Certified by Canadian Standards Association; SCM800E: Conforms to European Union Directives; Certified to EN60065; Eligible to bear CE Marking; Conforms to European EMC Directive 2004/108/EC; Meets Harmonized Standards EN55103-1:1996 and EN55103-2:1996 for residential (E1) and light industrial (E2) environments.
This product meets the Essential Requirements of all relevant European directives and is eligible for CE marking.
The CE Declaration of Conformity can be obtained from: www.shure.com/europe/compliance
Authorized European representative:
Shure Europe GmbH
Headquarters Europe, Middle East & Africa
Department: EMEA Approval
75031 Eppingen, Germany
Phone: +49-7262-92 49 0
Fax: +49-7262-92 49 11 4