uher SG 631 Logic User manual

TheSG631LOGICrepresentstheutmostintaperecordertechnologyoftoday.Asanaid
toyouinfamiliarizingyourselfwithitsnewtechniques,wearesupplyinghighlydetailedoper-
atinginstructionsandrecommendthatyoureadthemcarefully.If,however,youarealready
veryfamiliarwiththeoperationofmoderntapemachines,youwillsimplyneedtoreadcertain
sections.Eachchapterformsa closedunitandrefers,onlywhenabsolutelynecessary,to
otherpartsofthemanual,that,inturn,maybelocatedeasilybyusingthetableofcontents.
26

For full utilization of the new technologies offered by the SG 631, the points
belowshould be followedcarefully:
1. UseUHERNABAdapterZ 800toavoideventheslightestplaybetween reelandhub
shaft(seesec. 1.6).
2.UseUHER"professional"metalreels(Z827)astheyguaranteesmoothmovementfor
alltapetransportfunctionsanddecreasetapewear(seesec. 6.10).
3.UHER"professional"tapeZ 830isrecommendedforoptimumoperationalresultsand
bestelectro-acousticalvalues(seesec.6.10).
4.Alwaysusereelsofthesamesizeandofthesamematerialtogether(seesec. 6.10).
5.MakecertainthattheCUEINGswitchissetto"0"forallmodesofoperationexcept
CUEINGtoavoidtapespilling(seesec.3.18).
6.Makecertainthatthereelsizeswitchissettotheappropritateposition(seesec.3.24).
7.ReadChapter7 "CareandMaintenance"withespecialcare.
8.WhentheSG631isoperatinginthe fast-wind mode,forsafetyreasonsneithermove
itfromhorizontaltoverticaloperatingpositionnortouchthereelsunderanycondition.
9.AttheendoftheOperatingInstructionsyouwillfinda listofUHERaccessoryequipment
availablefromyourUHERdealertosupplementyourrecordingsystem.
27

Contents
28

29

1.SettinguptheSG631LOGICforRecordPlayback Operation
1.1AirCirculation
Thegreatestamountofheatdevelopsaroundthepowertransformer
whichislocatedatthecenteroftheventilatingslits.Theventilatingslits
mustbeleftfreeregardlessofthemachine'soperatingposition.When
installingthemachineina cabinet, a closedsectionofwallshelves,etc.,
becertaintoallowforsufficientaircirculationtoassureproperheat
exchange.
1.4A.C.MainsConnection,OperatingVoltage,Frequency,
MainsFuse
Themainsleadisattachedtothemachineandislocatedinthecov-
eredrecessinthefloor(orrear)ofthehousing(seeFig.1).Before
pluggingtheleadintoa mainspoweroutlet,ascertainthevoltageof
thepowersupply.
1.2OperatingPosition
TheSG631LOGICmaybeoperatedineitheruprightorhorizontal
position,orifdesired,inanytiltedposition.Inalloperatingpositions,
however,caremustbetakenthatthespoolsaresecurelyheldonto
thehubspindlesasdescribedinsec.1.6below.
1.3ExtendingConnectingLeads
WhenmatchingUHERplug-inextensionleadsarenotused,connecting
leadsshouldbeextendedonlybyanexperiencedservicetechnician
(seealso sees. 2.3,2.4and2.5). , " '-
TheSG631LOGICisfactory-settoanoperatingvoltageof220V,
butmaybeadjustedtooperateon 115 V A.C.Ifnecessary,setthe
voltageselectortothepropervoltage.
Beforeadjustingthevoltage,makecertainthatnoleadsareconnect-
edtoa mainspoweroutletandthatthemainsfuse,locatedinthe
fuseholder"A"(Fig.1)correspondswiththevoltagetobeselected.
Withtheaidofa coin,unscrewthefuseholder.Usea 0.8 A fusefor
220V A.C.,anda 1.6A fusefor 115 V.Oncetheproperfusehasbeen
inserted,theoperatingvoltagemaybechosenbyturningthevoltage
selector"B"(Fig.1)witha coin.Thevoltagevalueselectedwillappear
intherecess"C"(Fig.1)ofthevoltageselector.
30

Fig.1
It isnotnecessarytoadjusttheSG631LOGICtoa mainsfrequency
of50Hzor60Hzasthemachineuses D.C. motorsandthepower
supplyunitisdesignedforoperationwitheitherfrequency.
Note:
Extremeoverloadingofthepowersupplyunitorinternalshort-circuiting
activatesanautomaticguardcircuitthatswitchesoffthepowersupply
unit.Disengagingthenre-engagingthePOWERpush-buttonreturnsthe
guardcircuittoits"alert"function.FusesfortheD.C.voltagesinthe
machinemayalsoburnoutwhentheguardcircuitisactivated.Such
fusesshouldbereplacedonlybya servicetechnicianasthecauseof
theblow-outmustbedetectedand,ifnecessary,removed.
1.5MountingFeetforUprightOperation
Foruprightoperation,twofeet"D"areprovidedwitheachmachine
(seeFig.1).Tomountthem,firstlaythemachineononeside.Turn
fixingscrews"E"a fewtimesintothethreadings"F".Nextpushnotches
"G"inthefeet"D"undertheheadofthefixingscrews"E"untilthe
bridgecatchesingroove"I".Thentightenfixingscrews"E".
31

1.6MountingUHERNABAdapterZ 800for26.5cm (10%")
ReelsandLoadingTape
TheNABadaptermustbecarefullyplacedontherightand/orlefthub
spindle.First,pullupthethree-prongedmandrel(A)ofthespindle(see
Fig.2)andturnituntiltheprongsofthemovablesectionrestonthose
ofthestationarysection.Theinnerring(B)oftheNABadaptermust
alsobeturnedtotheleftuntiltheclampingjaws(C)forthethree-
prongedmandrel(A)areopenedsowidethattheadaptermaybeeasily
setuponthespindle.Oncetheadapterhasbeensetinplace(seeFig.3),
thethree-prongedmandrel(A)shouldbeturnedtotherightortothe
leftuntilitjumpsdownintothegroovesofthestationarysetion.The
adapteristhenpreventedfromfallingoff.Theinnerring(B)ofthe
clamping jawsshouldthenbeturnedtotheright,closingituntilthe
adapteristightlysecuredtothethree-prongedmandrel.Tighteningthe
clampingjawsisofparticularimportanceasitwillpreventanyplaybe-
tweenthemandrelandtheNABadapter.
NABadapterswithoutclampingjawscannotdoawaywiththeplay
betweenmandrelandadapter.Iftheplayistoogreat,however,poor
speedstabilityandpoortapewindmayresult.(MountingsuchNAB
adaptersandsecuringthemagainstfallingoffisbestaccomplishedas
describedforUHERNABadapters.)
32
h
Fig.2

Beforeplacinga 26.5cm (IOV2") reelontheNABadapter,turnthe
outerring(D)oftheadapteranti-clockwiseuntilthethreekeysofthe
movablepartoftheringareabovethoseofthelowerstationarypart
(seeFig.2).ThefullreeloftapeshouldbeplacedontheleftNAB
Fig.3
adapter,theemptyreelontherightadapter.Oncethereelisinplace,
turntheouterringoftheadapterclockwiseuntila clearstopisfelt
(seeFig.3).
Tothreadthetape,runa tapeleadofabout50cm(20")fromtheleft-
hand(supply)reel- withoutslack- pastthetapetensionsensorinto
thethreadingslotbetweenthefronttape-headcoverandthetape-
headassembly,outpasttherighttensionsensorontotheright(take-
up)reelandturnthetake-upreeluntilthesupplyreelisturnedalong
withit.OnpressingthepowerswitchandactuatingtheSTARTorFAST
FORWARDkey,thetapeleadwillwindontothetake-upreeluntilthe
transparentormetal-coatedswitchingfoilappears.Thefoilactivates
anautomaticshut-offswitchforalldeckfunctions.Thefoil-activated
switchmaybedisengagedbypressingthecounterresetbutton;hence,
withtheresetbuttondown,lightlytouchingtheSTARTorFAST
FORWARDkeywillbegintapetransportagain.Thezeroresetbutton©
mustbehelddownuntiltheswitchingfoilhasclearedthetapehead
assembly.
Note:Tapeswhichhavebeenplayedorrecordedonothertapemachines
mustbeinspectedtomakecertainthattheyaretightlywoundontothe
reel. If necessary,unwindandrewindthetapesonyourSG631before
usingthem torecordorreplay. ,
Tofacilitateloadingtapewhensmallsizedreels(under18cm)areused,
firstpressthePAUSE @ andCUEING @ keys;thendeactivatethem
afterloadingtapeonit.
33

*•'
1.7RecordOperationforUsersina Hurry
Asthequalityoftherecordingisessentiallydependentuponthecorrect
settingoftherecordlevel,thisstepshouldbegivenparticularattention:
1.Makecertainthattheinputsourcetobeusedinrecordingis
connectedandswitchedon.
2.PressPOWERswitch © (Checkconnectiontomainspoweroutlet).
FunctionindicatoraboveSTOPkeymustlightup.
3.Loadtapeandwindpastswitchingfoilontotake-upspool(see sees.
1.6 and3.15).
4.Seta)tapetypeswitch @ fortapeused(seesec.3.21),
b)reelsizeswitch @ (seesec.3.24),
c)modeselectorswitch(8)todesiredrecordmode(seesec.3.6)
and
d)tapespeedselector ® (seesec. 3.8).
5.Touchingthemlightly,oneafteranother,actuatetheRECORD®,
PAUSE @ andSTART (J3) keys.Thefunctionindicatorsabovethe
keyswilllightup.
6.Pressthezeroresetbuttonofthecountertomarkthebeginning
oftherecording.
7.Usingthemastercontrol(5), fadeinthedesiredinputsources
(seesec.3.3).
8.Usinglevelcontrols© to© , setmaximalrecordlevelforloudest
passagestoberecorded(see sees. 3.1and3.2).
9.PressLIMITERswitch © andchecksettingforcorrect(maximal)
recordlevel(seesec.3.5).
10.TipPAUSEkey©oncemore.Tapetransportandrecordingwill
begin.TippingthePAUSEkeystillagainwillinterrupttapemotion
andrecording.
11. Connectstereoheadphones(seesec.2.2)andadjusttheirvolume,
usingheadphonevolumecontrol@ . Checkrecordingacoustically
(asdescribedinsec.3.7)bypressingtheMONITORswitch(9)
12. LightlytippingtheSTOPkey © endsrecordoperation.
13. Toswitchtherecorderoff,pressthePOWERswitch © .
34

1.8PlaybackOperationforUsersina Hurry
Playbackmaybedirectlythroughthemachine'sheadphonespower
stage(whichpermitsconnectionoftwostereoheadphones)orthrough
theloudspeakersofyourhi-fisoundsystem.
Procedure:
4.Seta)tapetypeswitch @ fortapeused(see sec. 3.21),
b)reelsizeswitch@ (seesec.3.24),
c)modeselectorswitch (f) todesiredplaybackmode(seesec.3.6)
and
d)tapespeedselector ® (seesec.3.8).
1.Makecertainthattheamplifierconnectedforplaybackthroughthe
soundsystemspeakersisswitchedon- orthattheheadphones
areconnected(see sees. 2.2,2.4and2.7).
2.SwitchonrecorderbypressingPOWERbutton ©. Thefunctionindi-
catorabovetheSTOPkey © mustlight up.
3.Loadtapereelsandlock.Threadtapeandwindontotake-upreel
pastswitchingfoil(see sees. 1.6 and 3.15).
5.LightlytipSTARTkey ® . Thefunctionindicatorabovethekeyshould
lightup,andtapetransportshouldbeginassoonastheOMEGAloop
isformed.
6.Setvolumeasdesiredforheadphonesviaheadphonesvolume
control © , forloudspeakersviavolumecontrolsonthepowerampli-
fierofthehi-fisoundsystem.
7.Whenplaybackisthroughthesoundsystemamplifier,correcttone
andbalancesettings,ifneeded.
8.Ifnecessary,setMONITORswitch(9)inoff-TAPEposition.
35

2.Socketry
Dataonpinwiringaswellasinput/outputsensitivitiesandimpedances
aresuppliedasanaidtothetechnician(e.g.,inconstructingspecial
connectingleads)toassureoptimummatchingwithinputsourcesand
playbackequipment.
2.1MICROPHONE ©
Allcommerciallyavailablelow-impedancedynamicstereomicrophones
(200to500ohms)equippedwithDINplugsmaybedirectlyconnected
tothissocket.Forstereorecordingwithtwomonomicrophones, UHER
AdapterLeadK 626shouldbeused.Caremustbetakenthattheplug
oftheadapterisinsertedintothesocketfullyuptothestop.
UHERK 110istheextensionleadforusewithlow-impedancemono
microphones,K 134forusewithstereomicrophones(seelistofac-
cessoriesattheendoftheOperatingInstructions).
UHERdynamicstereomicrophone M 641andUHERelectretcondenser
microphone M 646maybedirectlyconnected.TheirearliermodelsM 640
and M 645,ontheotherhand,requireUHERAdapterK 822forcon-
nection.
Input signalsatpins3/2and5/2(2= ground)shouldbebetween0.1 mV
and80 mV. Allcommerciallyavailablecondensermicrophoneswith
(DIN45326)8-pinplugmaybeconnectedtothissocket.Thepluspole
ofthemicrophonepowersupply(+ 20V,sourceimpedance1.2 kohms)
islocatedatpin8.
2.2HEADPHONES(5-Pin) <^>
Thissocketisforconnectinga stereoheadphonesetequippedwith
a5-pinplug(likeUHER W 775)formonitoringrecordorplayback.All
highorlowimpedanceheadphonescurrentlyavailableonthemarket
maybeconnected(outputimpedance8 to2,000ohms).UHERAdapter
K633mustbeusedwhenconnectingheadphoneswithtwoLS-7plugs
(like UHERW 774).
Whenlisteningtoplayback,theMONITORswitch ® shouldbeinoff-
tape(TAPE)positionandthevolumeregulatedwiththeheadphones
volumecontrol d?) .
2.3HEADPHONES(PhoneJack) <®>
Thisfacilityisforconnectinga stereoheadphonesetequippedwith
ajackplug.Allhighorlowimpedanceheadphonescurrentlyavailable
onthemarketmaybeconnected(outputimpedance8 to2,000ohms).
Whenlisteningtoplayback,theMONITORswitch® shouldbeinoff-
tape(TAPE)positionandthevolumeregulatedwiththeheadphones
volumecontrol (f?) .
36

2.4DUBBINGOutput QO
Thissocketisforconvenienttapecopyingontoa second open-reei
orcassettetaperecorder.Using UHER StereoConnectingLeadK 541,
connectthisDUBBINGsockettotheRADIOsocketoftherecording
tapemachine.Outputsignalsdeliveredtopins3/2and/2(2= ground)
areapproximately750 mV (outputimpedancelessthan 15 kohms).
2.5RADIO Input/Output|j
Thissocketisa combinedinputandoutputforconnectiontoa stereo
tunerorreceiverwithDINstandardsockets.Forrecordorplaybackuse
UHERinter-unitStereoLeadK 541toconnecttheSG631LOGICto
theTAPEsocketofthetunerorreceiver.
Withmonoequipment,UHERAdapterK 837mustbeinsertedintothe
TAPEsocketofthemonosetbeforeusingtheK 541leadtomake
connectiontotheSG631LOGIC.
Toavoidlossofresponseinthehighfrequencyrangeduringrecord
andplayback,theconnectinglead(K541)shouldbeextendedonly
bya servicetechnician,andthenonlyiftheoutputimpedanceofthe
inputsourceortheinputimpedanceoftheplaybackequipmentper-
mits. Input signalsatpins1/2and4/2(2= ground)ofthissocketmay
bebetween1 mV and200 mV (inputimpedance27kohms).Forin-
putvoltagesover250 mV, itisadvisabletousethePHONOinputsocket.
Outputsignalsdeliveredtopins3/2and5/2(2= ground)areappro-
ximately750 mV (outputimpedancemaximum 15 kohms).
2.6PHONO Input©
Thissocket isTor connectingstereorecordplayerswithDINplugsand
crystalpickupcartridges.Recordplayerswithmagneticpickupmustbe
equippedwiththeirownequalizingamplifier.High-impedanceequip-
ment(e.g.stereotapeorcassetterecorders,stereoreceiversorUHER
mixerMix500A 124) mayalsobeconnectedtothissocket,usingUHER
StereoLead K 541.
Input signalsatpins3/2and5/2(2= ground)maybebetween80mV
and10V (inputimpedance680kohms).
2.7 DIA (Slide) ^
ThissocketisforconnectingautomaticslideprojectorsviaUHERPro-
jectorLeadK 911. Pins2 and3 areforslidechangingbysignalling
the "Dia-Pilot" oftheSG631LOGICtoscanthe1 kHzpulsesrecorded
onthetape.The"Dia"tapeheadrun-outtopins4 and6 (6= ground)
permitscontrolofmulti-visionprojectorsthatoperatewithpulsesup
to7 kHz.Inaddition,thistapeheadisalsoforrecordandplayback
ofthepulsesresponsibleforsynchronizingtaperecorderandprojector
in8 mmand 16 mmfilmdubbing.
37

2.8MONITOR5-PinOutput •-.'•*
ThissocketisforconnectingtheSG631LOGICtoanamplifierwith
amonitorinput,using UHER StereoConnectingLeadK 541.Usethe
amplifier'sswitchtoselect"fromsource"or"off-tape"monitoring.
Givecarefulattentiontotheinstructionsintheoperating manualof
theamplifier.
Outputsignalsdeliveredtopins3/2and5/2(2= ground)areappro-
ximately750 mV (outputimpedance 15 kohms).
2.9ACCESSORYA
Signalsdeliveredtothisoutputareapproximately750 mV perchannel
(outputimpedance15kohms).
2.11 INPUT 2 (Jack) fi' '.
ThisstereoinputisforconnectingtheSG631tohigh-levelinputsources
likestereorecordplayerswithcrystalpickupsystems,stereotape(open-
reelorcassette)recorders,stereotunersorreceivers.Stereorecord
playerswithmagneticpickupsmusthavetheirownequalizing pre-
amplifiertobeconnectedtothisinput.
Input signalsmayrangebetween80mVand10V (inputimpedance
680kohmsperchannel).
Thissocketisforconnectinga startingswitch(seesec.6.9)when
operatingwitha timer.WhenusingUHERTimerA 403,theSG631LOGIC
isautomaticallyswitchedtoRECORDandSTARTfunctionsassoonas
thetimerswitchesonthepowersupplyoftherecorder.ThePAUSE
functionmaybeswitchedbyremotecontrolifpins3 and4 ofthissocket
areconnectedtogether.
2.12 INPUT 1 (Jack) |i •
Thisstereoinputisformakingconnectiontolow-levelinputsources
havingoutputvoltagesbetween1 mV and200 mV.
Input signalsatthesejacksmayrangebetween1 mV and200 mV
(impedance27kohmsperchannel).
2.10MONITORJackOutput |lR
ThisstereooutputisforconnectingtheSG631toanamplifierwith
monitorswitching.Usetheamplifier'sswitchtoselect"source"or"off-
tape"monitoring,payingcarefulattentiontotheinstructionsintheoper-
atingmanualoftheamplifier.
2.13 OUTPUT(Jack)
®R
ThesestereojacksareforconnectingtheSG631tostereotuners,
receiversandamplifiersequippedwithjackconnectingfacilities.Out-
putsignalstrengthisapproximately750 mV perchannel(outputim-
pedance 15 kohms).
38

3.OperatingControlsandTheirFunctions
3.1MicrophoneRecordLevelControlsL 0 andR ©
Knobs© 1 and(2)areforsettingtherecordleveloftheleftandright
channels(respectively)ofa stereomicrophoneconnectedtothe
MICROPHONEinput.Whensettingtherecordlevel,themastercon-
trol©shouldbepushedtotheleftallthewaytothestop,thepeak
levellimiterremainingoutofcircuitforthemoment.Thecorrectrecord
levelhasbeenachievedwhenthecorrespondinglevelindicatorreg-
isters0 dBattheloudestpassagestoberecorded.TheLIMITERswitch(7)
maythenalsobepressed.Thepeaklevellimiterwillthusbeincircuit
andwillpreventoverloadingthetapebyreducingtherecordsignalto
amanageablelevelforthedurationofthesignalpeaksthatmaybe
incurred.Thefunctionindicatorbesidetherespectivelevelmeterwill
alwayslightupwhenthepeaklevellimiterisinoperation.Lightingup
brieflyandinnottoorapidsuccessionindicatesthatthelimiterisoper-
atingproperly.Lightingupoftenorconstantlyindicatesanincorrect
recordlevelsettingthatmayeasilyoccurduringmicrophonerecordings
whenthedistancefromthemicrophoneisdecreased.Thedegreeofthe
overloadisshownontherecordlevelmeter(seealsosec.3.4).The
recordlevelsettingmaybeacousticallycheckedbymakinga testre-
cordingandmonitoringthroughheadphoneswiththeMONITORbut-
ton(9)switchedfromTAPEtoSOURCEposition(seealsosec.3.7).
3.2 Radio/Phono RecordLevelControlsL (3)andR ©
Knobs(5)and© areforsettingtherecordleveloftheleftandright
channels(respectively)ofstereoinputsourcesconnectedtotheRADIO
orPHONOinputsockets.Whensettingtherecord level, themaster
control (D shouldbepushedtotherightallthewaytothestop.The
remainingprocedureisasdescribedinsec.3.1.
3.3MasterControl(5)forFadingin,OutorOverfromRadio/
PhonoInputstoMicrophoneInputduringRecord
Thisslidecontrolhasa middleclick-positionfromwhich- oncethe
recordlevelhasbeenset- radioorphonoinputsmaybeblendedover
torecordfromthemicrophone(see sees. 3.1and3.2).Fadingin,out
oroverofallinputsourcesconnectedandswitchedonmaybecon-
tinuousandcompletelyclick-free.Withthemastercontrolinmiddle
positionallinputsourcesareswitchedoutofcircuit.
3.4RecordLevelMeter©
Therecordlevelmeterhastwoseparateindicatorsystemswhich
registerpeakvaluesforthesignaltoberecorded.Theupperindicator
systemregisterstherecordleveloftheleftchannel,thelowersystem
thatoftherightchannel.
Therecordsettingdecisivelyinfluencesthequalityoftherecording.
Settingtheleveltoolow(under-recording)impairsthesignal-to-noise
ratiothatmaybeachievedbecausesignalstrengthwillnotbeableto
coverthetapehisssufficiently.
Settingtherecordleveltoohigh(overloading)increasesharmonic
39

3.OperatingControlsandTheirFunctions
3.1MicrophoneRecordLevelControlsL 0 andR ©
Knobs© 1 and(2)areforsettingtherecordleveloftheleftandright
channels(respectively)ofa stereomicrophoneconnectedtothe
MICROPHONEinput.Whensettingtherecordlevel,themastercon-
trol©shouldbepushedtotheleftallthewaytothestop,thepeak
levellimiterremainingoutofcircuitforthemoment.Thecorrectrecord
levelhasbeenachievedwhenthecorrespondinglevelindicatorreg-
isters0 dBattheloudestpassagestoberecorded.TheLIMITERswitch(7)
maythenalsobepressed.Thepeaklevellimiterwillthusbeincircuit
andwillpreventoverloadingthetapebyreducingtherecordsignalto
amanageablelevelforthedurationofthesignalpeaksthatmaybe
incurred.Thefunctionindicatorbesidetherespectivelevelmeterwill
alwayslightupwhenthepeaklevellimiterisinoperation.Lightingup
brieflyandinnottoorapidsuccessionindicatesthatthelimiterisoper-
atingproperly.Lightingupoftenorconstantlyindicatesanincorrect
recordlevelsettingthatmayeasilyoccurduringmicrophonerecordings
whenthedistancefromthemicrophoneisdecreased.Thedegreeofthe
overloadisshownontherecordlevelmeter(seealsosec.3.4).The
recordlevelsettingmaybeacousticallycheckedbymakinga testre-
cordingandmonitoringthroughheadphoneswiththeMONITORbut-
ton(9)switchedfromTAPEtoSOURCEposition(seealsosec.3.7).
3.2 Radio/Phono RecordLevelControlsL (3)andR ©
Knobs(5)and© areforsettingtherecordleveloftheleftandright
channels(respectively)ofstereoinputsourcesconnectedtotheRADIO
orPHONOinputsockets.Whensettingtherecord level, themaster
control (D shouldbepushedtotherightallthewaytothestop.The
remainingprocedureisasdescribedinsec.3.1.
3.3MasterControl(5)forFadingin,OutorOverfromRadio/
PhonoInputstoMicrophoneInputduringRecord
Thisslidecontrolhasa middleclick-positionfromwhich- oncethe
recordlevelhasbeenset- radioorphonoinputsmaybeblendedover
torecordfromthemicrophone(see sees. 3.1and3.2).Fadingin,out
oroverofallinputsourcesconnectedandswitchedonmaybecon-
tinuousandcompletelyclick-free.Withthemastercontrolinmiddle
positionallinputsourcesareswitchedoutofcircuit.
3.4RecordLevelMeter©
Therecordlevelmeterhastwoseparateindicatorsystemswhich
registerpeakvaluesforthesignaltoberecorded.Theupperindicator
systemregisterstherecordleveloftheleftchannel,thelowersystem
thatoftherightchannel.
Therecordsettingdecisivelyinfluencesthequalityoftherecording.
Settingtheleveltoolow(under-recording)impairsthesignal-to-noise
ratiothatmaybeachievedbecausesignalstrengthwillnotbeableto
coverthetapehisssufficiently.
Settingtherecordleveltoohigh(overloading)increasesharmonic
39

distortionandleadstoplaybackthatsoundstooshrillanddistorted.
Themaximalharmonicdistortionpermissibleis3%andisreachedwhen
thelevelmeterreads0 dBwiththemachinesetforfullrecordlevel
(usingDINreferencetape).Withthemaximalrecordlevelabove0 dB,
distortionrisesfarabove3%andrapidlysinksto1%orlesswiththe
maximalrecordlevelbelow0 dB.
Eachlevelregisteringsystemisequippedwithanilluminatedindicator
thatfunctionswhenthepeaklimiterisswitchedincircuit(seealsosec.
3.5).Althoughthefunctionindicatorsofthepeaklimiteraresignalled
paralleltothelevelindicators,itispossiblethatwiththelimiterin-circuit
its. function indicatorsmaylightupatbriefsignalpeaksevenifthelevel
meterdoesnotyetregister0 dB- becausethelevelindicatingsystems
areslightlysluggishduetothemassthatmustbemoved.Whensetting
therecordlevelwithoutusingthelimiter,however,thiseffecthasno
influenceuponthequalityoftherecordingastheresponsetimeofthe
levelmeteris sufficiently brief.(Eventhelightexposuremetersusedin
commercialsoundstudiosare"much"slowerthantheilluminated
functionindicatorswhichoperateinertialessly.)
Asidefromopticalcontrolbymeansoftherecordlevelmeter,an
acousticalcheckmaybemadeduringrecordwiththeaidofthemoni-
torswitch(seesec.3.7).Evenduringplaybackthetwoseparateindi-
catorsystemsofthelevelmeterregisterthepeakvaluesofthesig-
nalsrecordedonthetape.
3.5LIMITERSwitch ®
TheLIMITERbuttoncatchesindown-positionandswitchesonthepeak-
limitingcircuitthat,whentherecordlevelistoohigh(pointerinred
fieldofmeter),reducestherecordsignaltoa manageablelevelforthe
durationofthe overloading. Thedegreeofoverloadingisshownonthe
levelmeterwhilethetwofunctionindicators,locatednexttotheirre-
spectivelevelindicatingsystem,reflectthefunctioningofthelimiterby
lightingupfora relativelylongorshortperiod.Optimalrecordlevelhas
beensetwhenoneoftheilluminatedindicatorsflickersuponly
occasionally.Otherwisetherecordlevelmustbelowered,usingthe
appropriatelevelcontrol.Whenthelimiterswitchesonandoffinrapid
successionduetoanincorrectrecordlevelsetting,itcreatesa
"pumping"or"breathing"effectthatbecomesnoticeablethrougha
swellingandrecedingofthebackgroundnoise.
PressingtheLIMITERswitch ® a secondtimereleasesitintoitsup-
positionandswitchesoffthepeaklevellimitingcircuit.
3.6ModeSelector ®
TurningthisswitchsetstheSG631LOGICintoMONO,STEREOor
SLIDEoperatingmode.Inquarter-trackoperation(usingTapeHead
AssemblyZ 412),switchingtoMONO1 positionsetsthemachinefor
operationontrack1 ortrack4.Inhalf-trackoperation(usingTape
HeadAssemblyZ 402)MONO1 positionswitchestotrack1. Always
uselevelcontrol© or(3)tosetthemonorecordlevelthatinturn, will
beregisteredbytheupperindicatorofthelevelmeter.Similarly,with
theswitchinMONO2 position,track2 ortrack4 willbeusedinquarter-
trackoperationandtrack2 inhalf-trackoperation,withlevelcontrolsCD
or(3)usedforsettingtherecordlevel.TherecordlevelforMONO2
operation,however,isregisteredbythelowerindicatingsystemofthe
levelmeter.Duringmonooperationthelevelcontrols(2)and @ arenot
neededandshouldbefadedout.
40

WiththisswitchinMONO 1, MONO2 orSTEREO(quarter-trackstereo
operationusingTapeHeadAssemblyZ 412)thefulltake-upreelmay
beexchangedwiththeemptysupplyreelfora secondtapepassafter
thefirstpasshasbeencompletedandtapeiscompletelyontheright
(ortake-up)reel.Inhalf-trackstereooperationonlyonetapepassis
possible;hencethetapeshouldberewoundontotheleft(orsupply)
reeloncethetapeiscompletelyonthetake-upreel.
In half-trackoperationslidesynchronizationmaybeonlymonophonic,
butstereophonicinquarter-trackoperation.Thedifferencesbetween
half-trackandquarter-trackoperationaswellasthelocationofthe
controltrackforslideprojectoroperationareclearlyshowninFig.4.
Slidesynchronizationispossibleonlyatthe9.5or19cm/s {7W or 33A")
tapespeeds!
3.7MONITORSwitch©
Thispushbuttonisforselecting"off-the-tape"("B")or"fromsource"("A")
asthemodeofmonitoringduringrecord.Itallowsthequalityofthe
recordingtobecheckedacousticallyatonce,duringrecord,forin"B"
positionplaybackofthesignaljustrecordedisdirectlyoffthetape.On
theotherhand,with"A"monitoringthesignaldeliveredbytheinput
sourcemaybeheardwhileitisbeingrecordedonthetape.Thisdirect
comparisonofsourceandtaperecordingletsdifferencesbetweenthe
twobeeasilyrecognized.
WhentheswitchisinTAPEposition,a greenfunctionindicator
lightsupwhilea redilluminatedfunctionindicatorreflectsthe
SOURCEmonitoringposition.Bothfunctionindicatorsarelocatedabove
theMONITORswitch.
Fig.4
3.8TapeSpeedSelector ®
Turningthisswitchsetsthetapespeedat(4.7,9.5or 19 cm/s) 1Vs, 33A,
7V2 ips.AsmaybeseeninthePerformingSpecifications attheendofthe
OperatingInstructions,thehighestqualitydemandsarefulfilledatthe
71/2 speed.Note:Operationofautomaticslideprojectorsandmulti-
visionprojectorsispossibleonlyattapespeeds3%or 7V2 ips.
3.9 REC(ORD)Key©
PressingthiskeylightlysetstheSG631LOGICinrecordmode,and
settingtherecordlevelmaybeundertakenatonce.Makecertainthat
thetapetypeselectorisintheproperposition(seealsosec.3.21).
41

WhentheRECORDkeyisengaged,thefunctionindicatoraboveitis
lighted.ActualstartofrecordingisbegunbylightlypressingtheSTART
key(13).
WiththeREEL-SIZEswitch @ initsneutralup-positiontheSG631
LOGICissetfor(27cm) IOV2 spools.Iftapeon (13-18 cm)5"-7"spools
isused,presstheREEL-SIZEswitchintoitsdown-position.Theproper
greenfunctionindicatorabovetheswitchlightsuptoshowwhichreel
sizehasbeenselectedandset.
ThegreenfunctionindicatorabovethePAUSEkeylightsupwhenthe
keyisengaged.
3.13STOP Key©
Lightly pressing-the STOPkeydisengagesalldeckfunctionsdescribed
above.AslongastheSTOPkeyisengaged,thegreenfunctionindi-
catoraboveitwillremainlighted.
3.10Rewind
Pressingthiskeylightlysetsthemachineforfastrewind.Itmaybe
activateddirectlyfromanyotheroperating functionsetting.Whenthe
REWINDswitchisoperation,thegreenfunctionindicatoraboveit
lightsup.
3.14 FastForwardKey © • •
LightlypressingthiskeyswitchestheSG631LOGICtofastforward
wind.Itmaybeactuateddirectlyfromanyotherdeckfunctionsetting.
Whentheswitchisengaged,thegreenfunctionindicatoraboveit
lightsup.
3.11 START Key ®
OnlightlypressingtheSTARTkey,thetapeisformedintoanOMEGA
looparoundthecapstan,whereupontapetransportbegins.TheSTART
keymaybeactuateddirectlyfromanyotheroperatingfunctionsetting.
Whentheswitchisengaged,thegreenfunctionindicatoraboveit
lightsup.
3.12PAUSEKey®
Pressingthiskeylightlyinterruptstapemotionbegunwithactuationof
theSTARTkey.Tippingthekeya secondtimere-startstapemotion.
3.15 CounterwithZeroReset Button /Off-Switchfor
AutomaticShut-Off©
Pressingthezeroresetbuttoncancelsanygivenindexnumber,re-
turningthecounterreadingto"0000".Beforeeachrecording,itis
advisabletopresstheresetbuttonornotethestartingindexnumber.
Holdingthebuttondownswitchesofftheautomaticshut-offcircuit
thatisnormallyactuatedbythefoil(transparentormetal)atthebe-
ginningorendofthetape.Thenuponpressingoneofthetapetrans-
portkeys,theswitchingfoilwillmoveawayfromtheswitch-offcontacts
orlightbarriers.
42

3.16POWER On /OffSwitch
3.19 "DIA"(SlideControlPulse)Button©
Pressingthislock-downpushbuttonintodown-positionswitchesonthe
powersupplyoftheSG631LOGIC.Thelevelmeterandthefunction
indicatorabovetheSTOPkeywillthenlightup,aswellasoneofthe
twoMONITORfunctionindicatorsandoneofthefunctionindicatorsfor
thereel-sizeswitch.PressingthePOWERbuttononcemoreswitches
offthepowersupply,andthebuttonwillreturntoitsup-position.
3.17HeadphonesVolumeControl ©
Thisknobisforlinearvolumeregulationofstereoheadphonescon-
nectedtotheSG631LOGIC.Turntheknobclockwisetoincrease
thevolume,anti-clockwisetodecreaseit.
3.18CUEINGSwitch ®
"Cueing"inthesenseof"givingthesignalorkey-wordtobegin"gives
thebestideaofwhathappensintheCUEINGprocess.A certainspot
ona recordedtapeislocatedinordertobegina newrecordingorto
beginplaybackofa particularpassage,ortoedit(splice)tape:asis
everydaypracticeinprofessionalstudiorecording.
Theapproximatelocationofa particularspotonthetapecanbeac-
complishedbyusingthefast-forwardorrewindmodesplustheindex
counter.Forexactlocation,however,switchtheSG631toPAUSEand
playback,thenactivatetheCUEINGswitch(turnswitchtoposition1);
thetapereelsmaythenbeturnedbyhand.Slowlyturningthetake-up
reelwithonehandwhileslightlybrakingthesupplyreelwiththeother
permitstheplaybacktobeheardatrelativelynormalpitch.
Pressingthisbuttonwillrecorda slide-changingpulse(1 .kHz) onthe
controltrackofthetapeifthemodeselector (§) issettoDIA(toswitch
onthecontrolsignalgenerator)andtheRECORDkey @ hasbeen
actuated.
3.20OUTPUTLEVELControl @
TurningthisswitchsetstheoutputsignaldeliveredtotheRADIOsocket
andpermitsmatchingtheoutputleveloftheSG631LOGICtothat
ofa secondsoundsourcewhenconnectedtoanamplifiernotequipped
witha variableinputlevelcontrol.Withthevolumecontrolofthe
amplifierinthesamepositionwhenswitchingfromtapeplaybackto,
forexample,phonoplayback,thevolumelevelshouldremainunchanged.
Withtheoutput levelcontrolinmiddleposition,anoutputsignalof
750 mV perchannelisdeliveredtotheRADIOoutputsocket.Turning
thelevelcontrolclockwiseraisestheoutputvoltage(uptoapproxi-
mately1.2V perchannel).Turningitanti-clockwiselowerstheoutput
signal(downtoapproximately500 mV perchannel).
3.21TAPESELECT Switch
Turnswitchtosetthemachinetostandardferricoxidetape(Fe-
position)ortoferrichrometape(FeCr-position).Thelatterhastwo
magneticcoatingsanda highfrequencyoutputofapproximately4 dB
betterthanthatofstandardtape.
43