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2 5

S

TEREO 

O

PERATION

Compressing a two-channel (stereo) signal with two independent compres-
sors creates a problems: if one channel is compressed more than the other,
the stereo image will shift to one side, causing an imbalance in the perceived
stereo sound field.  To prevent shifting, DOD has incorporated a Stereo Link
switch on the 866.  This switch allows both channels to track in perfect uni-
son while the detectors for each channel operate independently.  When the
Link switch is depressed, the detectors are tied together and both channels
react to the higher of the two channel signals.  This eliminates channel over-
ride, and the stereo image is preserved.

S

PECIAL 

A

PPLICATIONS

The uses for a compressor don't end with compression and protective limit-
ing.  Applications such as "ducking", "de-essing", and "de-thumping" can be
achieved with equal ease, and their uses are many.

The 866 provides Side Chain Inputs and Outputs, which allow direct access to
each channel's detector circuits.  Since the detectors control the compressing
VCA (voltage-controlled amplifier), one can control the program material with
a completely unrelated signal.  This is done by inserting the control signal into
the Side Chain Input.

Ducking is a good example of this type of application. Ducking is simply gain
reduction of a signal when another is present.  This technique is widely used
in sports broadcasting to reduce the level of the crowd background signal
when the announcer is speaking.  The preamplified voice of the announcer is
sent to a side chain input to compress the noise of the crowd.  The voice and
crowd signals are then mixed together.  For this type of application, the com-
pression ratio is kept fairly low with long attack and release times.  

The Side Chain output is provided so that the controlling signal (not the pro-
gram material) may be modified before reaching the detectors.  

The most common use of this technique is for de-essing.  A de-esser reduces
the high frequency sibilance in the "s"s and "t"s of speech to prevent tape sat-
uration or high frequency driver damage.  Connect the Side Chain Output to
an equalizer whose output is connected to the Side Chain Input of the 866.  

The areas where most of the "ess" energy is located are between 2.5 kHz and
10 kHz.  If these areas are boosted on the equalizer, the gain of the program
material will be reduced more by the compressor because of the excess gain

Signal Processors 18-0121-B  6/8/99  10:25 AM  Page 25

Summary of Contents for 834 II Series

Page 1: ...C O N T E N T S R T A S E R I E S I I 2 8 3 4 8 3 5 S E R I E S I I 11 8 4 4 S E R I E S I I 17 8 6 6 S E R I E S I I 20 1 Signal Processors 18 0121 B 6 8 99 10 24 AM Page 1...

Page 2: ...POWER SOCKET Do not use the mains plug without the fuse cover in place Replacement fuse covers can be obtained from your local retailer Replacement fuses are 13 amps and MUST be ASTA approved to BS13...

Page 3: ...are should be taken so that objects do not fall and liquids are not spilled into the enclosure through openings POWER SOURCES The appliance should be connected to a power supply only of the type descr...

Page 4: ...it covers The RTA Series II includes a calibrated audio measurement microphone This microphone is equipped with a 40 foot cable which enables you to position the microphone in several locations in the...

Page 5: ...trol This control sets the input level from the calibrated microphone input jack the line level input jack or the auxiliary microphone input jack Use this control to set the response of the display to...

Page 6: ...ound In order to make the necessary changes of frequency response in an audio system you will need to have either a graphic equalizer or parametric equalizer Since the RTA measures in 1 3rd octave inc...

Page 7: ...with an indoor sys tem so that you make the first adjustments to the system inside this critical distance before the reverberation of the room environment has a chance to affect the response of the sy...

Page 8: ...st the monitors Make sure that you turn down the input to the system then increase the pink noise level to a convenient measuring level Use just enough level from the RTA to overcome any ambient room...

Page 9: ...sound This is the best way to minimize feedback and get the highest sound level from the monitors but you will sacrifice some sound quality Once you ve equalized the system with one of the above proce...

Page 10: ...electret condenser type RTA powered Microphone Sensitivity 64 dB 3 dB 0dB 1V bar 1kHz Microphone Frequency Response 20 Hz to 20 kHz 1 dB Auxiliary Microphone Input XLR type connector balanced Auxiliar...

Page 11: ...els as a full range amplified system with more power The greatest power demands in a sound system are made by the low fre quencies of the program material This is because music and voice signals cont...

Page 12: ...power cord away from audio lines and plug into a convenient outlet Connect audio lines to the crossover using the appropriate input jacks to channels 1 and 2 for stereo operation or to channel 1 only...

Page 13: ...r speaker and driver manufacturer s specifications for the recom mended crossover frequencies Basic setup procedures for the crossovers are as follows Label each power amplifier for its respective fre...

Page 14: ...ied from 100 Hz to 10 kHz Connect the outputs of the crossover to the appropriate amplifiers THE POWER AMPLIFIERS SHOULD STILL BE UNPOWERED Check to see that all crossover level controls are set to an...

Page 15: ...tereo Mono switch LED indicator lit When operating the crossover in stereo mode the MID HIGH frequency control of the 834 is vari able from 75 kHz 7 5 kHz When operating the crossover in mono mode the...

Page 16: ...ced unbalanced connections Outputs 1 4 tip ring sleeve phone jacks for balanced connections and 1 4 tip sleeve phone jacks for unbalanced con nections 835 XLR Inputs balanced female XLR Outputs balanc...

Page 17: ...nput and output jacks are made using balanced tip ring sleeve or unbalanced 1 4 tip sleeve phone plugs FOR BALANCED CONNECTION wire the plug as follows Tip high Ring low Sleeve ground FOR UNBALANCED C...

Page 18: ...ions of speech such as ends of sentences This choppiness can be cor rected by lowering the Threshold This will still yield good noise gating per formance without cutting off the voice The Ext Key func...

Page 19: ...the gate You may find something you like The Control output is a unique feature of the 844 Series II This output can be used to trigger a drum machine or sequencer in time with whatever is input into...

Page 20: ...cks on the compressor FOR BALANCED CONNECTION Use 1 4 tip ring sleeve phone plugs wired as follows tip high ring low sleeve ground FOR UNBALANCED CONNECTION use either 1 4 mono phone plugs or RCA phon...

Page 21: ...al above the Compressor Threshold level setting Attack This control adjusts the speed with which the compressor reacts to an increase in input signal level above the threshold Shorter attack time set...

Page 22: ...ng control of the compressor with another signal for such applications as ducking When used with the Side Chain Output the original input signal can be modified for applications such as de essing Inse...

Page 23: ...erall dynamic range of a signal while still preserving the nat ural open feel of the sound For limiting the Attack time should be short so that potentially damaging transients don t get past the limit...

Page 24: ...ll signals will pass through The Output Gain control allows the user to make up for gain lost in the com pression process and to set the output level of the compressor for compati bility with other eq...

Page 25: ...signal This is done by inserting the control signal into the Side Chain Input Ducking is a good example of this type of application Ducking is simply gain reduction of a signal when another is presen...

Page 26: ...dB Input Impedance 20 K unbalanced 40k balanced Maximum Input Level 21 dBu ref 0 775 Vrms Output Impedance 51 unbalanced 102 balanced Maximum Output Level 21 dBu ref 0 775 Vrms Side Chain Input Imped...

Page 27: ...C C C C O O O O R R R R P P P P O O O O R R R R A A A A T T T T I I I I O O O O N N N N O O O OW W W WN N N NE E E ER R R R S S S S M M M MA A A AN N N NU U U UA A A AL L L L S S S SI I I IG G G GN N...

Page 28: ...L DISTRIBUTION 3 OVERLOOK DR UNIT 4 AMHERST NEW HAMPSHIRE 03031 U S A FAX 603 672 4246 DOD IS A REGISTERED TRADEMARK OF DOD ELECTRONICS 1994 DOD ELECTRONICS CORPORATION PRINTED IN U S A 2 94 MANUFACTU...

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