McIntosh MA6 Guide

MULTIPLEX
ADAPTER
MA6
GENERALDESCRIPTION
UsetheMclntoshMA6MultiplexAdapterto
hearFMstereofromtheMR66FMTuner.
Careful,thoroughengineeringandsuperiorde-
signingeliminatetheneedforcriticaladjust-
mentinthefield.
Inmultiplexbroadcasting,bothleftand
rightchannelsofa stereoprogramaretrans-
mittedoveroneFMstation.Thesimplebroad-
castingofleftchannelandrightchannel
neededonebasicimprovement.Thosewhodid
nothavemultiplexequipmentwouldonly
receivehalfa program.A newbroadcasttech-
niquecalledmatrixingwasdevelopedtoover-
comethisproblem.Inthenewtechniquethe
leftandrightprograms(L+ R)areaddedelec-
tronically.TheL+ R signaliscenteredona
portionofthestation'sassignedspectrum
calledthemaincarrier.Atthesametimethe
leftandrightprogramsaresubtracted(L-R).
TheL—R signaliscenteredonanotherportion
ofthestation'sassignedspectrumcalledthe
sub-carrier.(TheFCCalsopermitsthesta-
tions,iftheychoose,touseanotherpartofthe
assignedspectrumfornonstereomusictrans-
mission.ThisadditionalprogramiscalledSCA,
sub-carrierauthorization.Themultiplexunit
electronicallyprotectsyourstereolisteningby
preventingSCAfrominterfering.)
Ina FMtunerreceivingmultiplex,thesig-
nalsareagainmatrixed.Thematrixinginthe
tunerseparatesthetwochannelssothatwe
hearthebroadcastasstereo.Theprocess
writtenalgebraicallyis:(L+ R)+ (L-R)= 2L;
(L+ R)- (L-R)= 2R.Ina FMtunernot
equippedwitha multiplexdecoder,thebroad-
castisheardasL+ R,a completemonophonic
program.
TECHNICALDESCRIPTION
TheMA6MultiplexAdapterusesa special
Mclntoshdevelopeddetectingcircuit.Oneof
theadvantagesofthiscircuitistheelimina-
tionofthecriticaladjustmentsnecessarywith
commonlyusedmatrixingmethods.
Atemperaturestabilized19KCamplifier
locks-ina highlystablepush-pullsynchronous
oscillator.Apartfromotheradvantagesthis
methodprovidesgreatestnoiseimmunity.
Balanceddetectorscancel19KCand38KC
componentsintheoutputandassurelownoise
anddistortion.
Athree-sectionsharpcut-offfilterrejects
SCAinterferenceandreducessusceptibility
tospurioussignals.
SPECIFICATIONS
Weight:1 Ib.2 oz.
ShippingWeight:1 Ib.10oz.
Dimensions:21/8incheswide;3¾incheshigh
83/16inches long.
HumLevel:Betterthan60dbbelow100%
stereomodulation.
Distortion:Lessthan0.3%(MultiplexUnit
only).
Suppressionofpilot(19KC)andCarrier
(38KC):Greaterthan40dbbelow100%
modulation.

TheMA6canbeconvenientlymountedtoa
shelforcabinet.Fourwoodscrewsaresup-
INSTALLATION
MA6MULTIPLEXDECODER
Figure1.MA6MultiplexAdapterConnectedtothe
MR66BackPanelShowingMultiplex
AdapterEndView.
CONNECTING
TheMA6multiplexadapterpowercableis
thegraycableattachedtothemultiplex
adapterchassis.Ontheendofthiscableisa
five-prongplug.Aligntheprongsoftheplug
withthepowerreceptaclemarkedFMMULTI-
PLEXPOWERonthebackpaneloftheMR66
stereotunerandplugtheconnectorin.
Three24inchgraycablesaresuppliedwith
theMA6.Usethesecablestocompletethe
connectionoftheMA6totheMR66Stereo
Tuner.
Connectthecablesasfollows:
1)Connecta cablebetweenthereceptacle
markedINPUTontheMA6chassistothe
receptaclemarkedFMMULTIPLEXOUT-
PUTonthebackpaneloftheMR66.
2)Connecta cablebetweenthereceptacle
markedOUTPUT1 ontheMA6chassisto
thereceptaclemarkedMULTIPLEXIN-
PUTS1 onthebackpaneloftheMR66.
3)Connecta cablebetweenthereceptacle
markedOUTPUT2 ontheMA6chassisto
thereceptaclemarkedMULTIPLEXINPUT
2onthebackpaneloftheMR66.
IMPORTANT
Thenumbers1 and2 onthebackpanelof
theMR66designatetheleftandrightchan-
nels,respectively.
ANTENNACONSIDERATIONS
Forthesatisfactoryoperationofa multiplex
tuner,moresignalisneededthanformono-
phonicreception.Monophonicinstallations
thatweresatisfactoryonanindoorantenna
mayrequiretheuseofanoutdoorantennafor
equivalentresults.Satisfactorystereorequires
about10timesasmuchsignalfromthean-
tenna.
LABORATORYINC.
2.5M-AA134-113
2ChambersStreet
BINGHAMTON,N.Y.
ENDVIEW
ENDVIEW
pliedwiththeMA6tosecureit.