Mackie 2404 Musical Toy Instrument User Manual


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17
Owner’s Manual
Atthemaximumcompression,thethresholdissetat
0dBu,andtheinputtooutputrelationshipis
representedbythelowercurve.Iftheinputis-5dBu
(thatis,belowthethreshold),theoutputis-5dBu.As
theinputreaches0dBu,theoutputisabitlessthan
0dBu.Iftheinputis+5dBu,theoutputisabout
+2dBu.Iftheinputreaches+10dBu,thentheoutput
is+3dBu.Noticetheshapelycurveofthesoftknee
betweenthediagonalslopeofx=yandthecompressor
slopeof6:1(thecompressionratio).
Theotherbluecurvesrepresentin-betweenpositions
ofthecompressorknob,withhigherthresholdsbefore
compressionbegins.
Outboardcompressorsoftenhavecontrolssuchas
compressionratio,threshold,softknee/hardknee,
attack time, and release time. These last two affect how
quicklythecompressorkicksinwhentheinputexceeds
thethreshold,andhowquicklyitisreleasedafterit
dropsbelowthethreshold.Inthiscompressor,these
parametersarespeciallychosentogiveyouthebest
overallperformance.
Adjustthethresholdcarefully,soyourdynamicrange
isstilllovely,withoutdistortionoroverloadduringthe
performance.Runthroughafewpracticescreamsand
high-notes,andadjustthecompressionasrequired.
26. Compressor
Eachofthelastfourmonochannelsinthe
VLZ44•Busmixerhasanin-linecompressorcircuit
withavariablethreshold.Thisisveryusefulfor 
compressionofvocals,andsnaredrums,forexample,
soyoumightconsiderconnectingyourmicrophones
anddrummicstothesechannels,ratherthanother
channels.
Whentheincomingsignalsexceedthethresholdlevel
setbythisknob,thesignallevelisautomatically
compressed.Thisreducesthedynamicrange,and
reducesthechanceofdistortionduetooverloadingthe
inputsignals.
Dynamic range is the difference in level
betweenthequietestandloudestpartsofa
song.Acompressor“squeezes”thedynamic
range,resultinginanoverallsteadier,moreconstant
volumelevelforthesignal.Ithelpssources,suchas
vocals,“sit”properlyinthemix;itisveryusefulforlive
sound.
Thecompressionratioisxedataround6:1,with
asoftkneeresponse.Thethresholdmaybeadjusted
clockwisefromoff(nocompression)to0dBu(max).
Asanexample,supposethethresholdissetto
maximum.Anincomingsignalreachesthethresholdof
0dBu.Asitincreasesbeyondthethreshold,itbecomes
compressedataratioof6:1.Thismeansthatevenifthe
inputfurtherincreasesby6dB,theactualoutputonly
increasesby1dB.Thiscompressestheoutputsignal,so
thereismoreprotectiontoyoursystemfromdistortion
andoverloadduetopoormicrophonetechnique(say
itain'tso)andgeneralpops,bangsandheavymetal
screaming.Thesoftkneemeansthatthecompression
slowlyrampsupto6:1fromthethreshold.Itdoesnot
jumpabruptlyto6:1,asthiswouldbehardknee
compression,andharderontheearstoo.
Thegraphonthispageshowstheinputsignallevel
goingintothecompressor,versustheoutputlevel 
comingoutofit.Itisthetypicalgraphtoseewhen
compressorsarediscussed,andisjustthekindofthing
ourengineersliketodiscussduringthecompany
Christmasparty*.
Ifthecompressorisoff,thentheinput=output.For
exampleaninputsignallevelof+5dBuresultsinan
outputlevelof+5dBu.Thediagonallinefromlowerleft
toupperrightrepresentsx=y,thatis,input=output.
+20
-10
-5
+0
+5
+10
+15
+20-10 -5 +0
SLOPE 6:1
SOFT KNEE
SLOPE 1:1
+5 +10 +15
INPUT SIGNAL STRENGTH dBu
OUTPUT SIGNAL STRENGTH dBu
OFF MAX
COMP
OFF MAX
COMP
OFF MAX
COMP
*MyHighSchoolmathteacher,Mr.Marvin,thoughtthat
graphsmightcomeinhandyformeoneday.Finally!
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