Unicorn Digital Timepiece User manual

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Cambridge,MA02138
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Website:http://www.motu.com
Mark of the Unicorn, Inc.
Digital Timepiece
User’s Guide

SAFETY PRECAUTIONS AND ELECTRICAL REQUIREMENTS
WARNING:TO REDUCETHE RISK OF FIRE OR ELECTRICAL SHOCK,DO NOT EXPOSETHIS APPLIANCETO RAIN OR OTHER MOISTURE.
CAUTION:TO REDUCETHE RISK OF ELECTRICAL SHOCK, DO NOT REMOVE COVER.NO USER-SERVICEABLE PARTS INSIDE.REFER SERVICINGTO
QUALIFIED SERVICE PERSONNEL.
WARNING:DO NOT PERMIT FINGERSTOTOUCHTHETERMINALS OF PLUGSWHEN INSTALLING OR REMOVINGTHE PLUGTO OR FROMTHE OUTLET.
WARNING:IF NOT PROPERLY GROUNDEDTHE DigitalTimepiece COULD CAUSE AN ELECTRICAL SHOCK.
TheDigitalTimepieceisequippedwithathree-conductorcordandgroundingtypeplugwhichhasagroundingprong,approvedbyUnderwriters'LaboratoriesandtheCanadianStandardsAssociation.
This plug requires a mating three-conductor grounded type outlet as shown in Figure A below.
Iftheoutlet youareplanningto usefortheDigitalTimepieceis ofthetwoprong type,DONOTREMOVEORALTERTHEGROUNDINGPRONGINANYMANNER.Useanadapterasshownbelow
and always connect the grounding lug to a known ground.It is recommended that you have a qualified electrician replace theTWO prong outlet with a properly groundedTHREE prong outlet.An
adapter as illustrated below in Figure B is available for connecting plugs to two-prong receptacles.
WARNING:THE GREEN GROUNDING LUG EXTENDING FROMTHE ADAPTER MUST BE CONNECTEDTO A PERMANENT GROUND SUCH ASTO A
PROPERLY GROUNDED OUTLET BOX.NOT ALL OUTLET BOXES ARE PROPERLY GROUNDED.
If you are not sure that your outlet box is properly grounded, have it checked by a qualified electrician.NOTE:The adapter illustrated is for use only if you already have a properly grounded two-prong
receptacle.Adapter is not allowed in Canada by the Canadian Electrical Code.Use only three wire extension cords which have three-prong grounding type plugs and three-prong receptacles which
will accept the DigitalTimepiece plug.
IMPORTANT SAFEGUARDS
1. Readinstructions -Allthesafetyandoperatinginstructionsshouldbereadbeforeoperatingthe DigitalTimepiece.
2. Retaininstructions -Thesafety instructions and owner'smanualshould be retained forfuture reference.
3. HeedWarnings-All warningsontheDigitalTimepiece and in the owner'smanualshould be adhered to.
4. FollowInstructions -Alloperatingand use instructionsshouldbe followed.
5. Cleaning-UnplugtheDigitalTimepiece from the computer beforecleaning and use adampcloth.Do not use liquidoraerosolcleaners.
6. Overloading-Do not overloadwalloutlets and extensioncords as this canresultinariskoffireorelectricalshock.
7. PowerSources-This DigitalTimepiece should be operatedonlyfromthe type of powersourceindicatedon the marking label.If youare not sure of the typeofpowersupply to yourlocation, consult yourlocalpowercompany.
8. Power-CordProtection-Power-supplycordsshouldbe routed so that theyarenot likelytobewalkedonorpinchedby itemsplaceduponoragainstthem.Pay particular attention tocordsandplugs,conveniencereceptacles,and
thepointwherethey exitfrom the DigitalTimepiece.
9. Lightning-ForaddedprotectionfortheDigitalTimepiece duringalightningstorm, unplug itfromthewalloutlet.This will prevent damagetotheDigitalTimepiece due to lightning andpowerline surges.
10. Servicing - Do not attempt toservice this DigitalTimepiece yourselfasopening or removingcoverswillexpose youto dangerous voltageandotherhazards.Referall servicingtoqualifiedservice personnel.
11. DamageRequiring Service-Unplug the DigitalTimepiece from thecomputerandreferservicing to qualified servicepersonnelunderthefollowing conditions.
a. Whenthepower supplycordorplugisdamaged.
b. Ifliquidhasbeenspilledor objects havefalleninto the DigitalTimepiece.
c. IftheDigitalTimepiece has been exposedto rain orwater.
d. IftheDigitalTimepiece does not operatenormally byfollowingtheoperatinginstructionsinthe owner's manual.
e. Ifthe DigitalTimepiece has been droppedorthecabinethasbeen damaged.
f. Whenthe DigitalTimepieceexhibitsa distinct changeinperformance, this indicates aneedforservice.
12. ReplacementParts -Whenreplacementparts are required,besure theservice technician hasusedreplacement partsspecifiedbythemanufacturer orhave the samecharacteristicsasthe original part.Unauthorizedsubstitutions
mayresult in fire,electricshockor other hazards.
13. SafetyCheck-Uponcompletion of anyservice or repairs to this DigitalTimepiece,ask the service techniciantoperformsafetychecksto determinethattheproduct is in safeoperating conditions.
ENVIRONMENT
OperatingTemperature:10°C to 40°C(50°Fto104°)
AVOIDTHE HAZARDS OF ELECTRICAL SHOCK AND FIRE
Donothandlethepowercordwithwethands.Donotpullon the powercordwhendisconnecting it from an ACwall outlet.Grasp it bytheplug.
INPUT
LineVoltage:100 - 120 voltsAC,RMS(USandJapan) or220-250voltsAC, RMS (Europe).Frequency:47 - 63 Hzsinglephase.Power:7wattsmaximum.
CAUTION: DANGER OF EXPLOSION IF BATTERY IS REPLACED.REPLACE ONLYWITHTHE SAME OR EQUIVALENTTYPE RECOMMENDED BYMANUFAC-
TURER.DISPOSE OF USED BATTERY ACCORDINGTO MANUFACTURER’S INSTRUCTIONS.
3-prong plug
Grounding prong
Properly grounded 3-prong outlet
Grounding lug
Screw
3-prong plug
Adapter
Makesurethis isconnected
to a known ground.
Two-prong receptacle
Figure A Figure B

CHAPTER
3
Contents
Chapter1–
Aboutthe DigitalTimepiece
5 Packinglist
5 Aboutthis guide
5 Registerfor technicalsupport
5 Whatis theDigitalTimepiece?
Chapter2–
Degreesof Accuracy
9 Beforeyou goanyfurther…
9 Sample-accuratesync
9 Frame-accuratesync withphase-lock
10 Frame-accuratesync
10 Frame-accuratetriggering
11
FrontPanelQuick Reference
12
RearPanelQuick Reference
Chapter3–
Installation
13 Overview
14 Computers
16 DigitalMultitracktapedecks
18 WorkingwiththeTascamDA-88
22 WordClockDevices
24 S/PDIFdevices
27 Video
28 SMPTEtimecodedevices
29 MIDITimeCodedevices
29 AlesisLRC
30 MMCcontrolsurfaces
Chapter4–
FrontPanel Settings
33 Overview
34 Aboutsynchronization
34 Choosinga timebasemode
36 Internal
36 MTC
36 LTC
36 Video/Internal
36 Video/MTC
36 Video/SMPTE(LTC)
37 Video/VITC
37 Video/Sony
37 Word1x/Internal
37 Word1x/MTC
37 Word1x/LTC
37 Word256x/Internal
37 Word256x/MTC
38 Word256x/LTC
38 Word1x/Video/Internal
38 Word1x/Video/MTC
38 Word1x/Video/LTC
38 Word1x/Video/VITC
38 Word1x/Video/Sony
39 S/PDIF/Internal
39 Controltrack 1or2
39 Word1x/Control track1or 2
39 DA-88
39 Word1x/DA-88
39 ADAT
39 Word1x/ADAT
40 theSMPTE frameratesetting
41 TheWord clockratesetting
Chapter5–
ExampleSetups
45 Overview
45 TheDigital Timepieceasmaster
46 Videoas timebasemaster
47 Devicesthat cannotactas aslave
48 Usingan AlesisBRCor TascamRC-848
Chapter6–
Converting/GeneratingTime Code
49 Overview
49 Startingplayback
49 Deferredplayback
50 Generatingor Convertingtimecode
Chapter7–
StripingTime Code
53 Overview
54 Generalprocedure
55 Stripingframe-locked LTContovideo
55 StripingSMPTE onamultitrack tapedeck
55 Regeneratingfresh timecode
56 Lengtheninga SMPTEtrack
57 Regenerationand timecodebits
57 RecordingVITC

4
58 Recordingburn-in & othergraphics
Chapter8– MIDIMachine Control
59 Overview
59 HowMMC works
59 Arecommended scenarioforMMC
60 MMCDevice IDs
62 Settingup MMCslaves
63 Settingup aMMCtransport master
64 MMCcontrol ofrecordfunctions
Chapter9– DigitalTimepiece &Performer
67 Overview
67 GettingtheDigitalTimepiecetoappearinPer-
former’sMMC window
67 SlavingPerformer
68 UsingPerformer astransportmaster
69 MMCrecord commands
71 Videostreamers
72 Controllinga DA-88/SY-88withPerformer
Chapter10– DigitalTimepiece &Other
Sequencers
75 Overview
75 Establishingcommunication
75 Slavingyour sequencer
76 Usingyour sequencerastransport master
77 MMCrecord commands
Chapter11– DigitalTimepiece &OMS
79 Overview
79 ClockWorksand OMS
81 PreparingClockWorks
81 PreparingOMS
81 Addingthe DTPtoyour OMSsetup
82 UsingAV Controls
Chapter12– DigitalTimepiece &ProTools
83 Overview
84 ProTools, ClockWorks,OMS& FreeMIDI
85 EnablingOMS emulationinFreeMIDI
85 PreparingOMS
86 ProTools asmaster
88 ProTools asslave
91 ProTools andTriple-sync
91 Transportcontrol
92 Lockuptime
Chapter13– AlesisLRC
93 Usingan AlesisLRC
93 LRCbutton functions
94 LRCCalibration
Chapter14– Troubleshooting
95 Commonproblems andsolutions
98 CustomerSupport
98 ReplacingDisks
98 TechnicalSupport

CHAPTER
5
1 AbouttheDigitalTimepiece
Thankyouforpurchasingthe Digital Timepiece™!
PACKING LIST
Your Digital Timepiecebox shouldhave the
followingitemsin it.If not,contactMarkof the
Unicorncustomerserviceat(617) 576-2760.
■
DigitalTimepiece
■
Power cord
■
DigitalTimepieceManual
■
ClockWorks™Manual
■
ClockWorks™softwareinstallerdisks
■
Registration card
ABOUT THIS GUIDE
Thisguide providesimportantinformationabout
installingand setting uptheDigitalTimepiece.
There isa companionguidefortheMacintosh
softwareconsolethatshipswiththeDigital
Timepiececalledthe
ClockWorksUser’sGuide .
REGISTER FOR TECHNICAL SUPPORT
Beforeyougoany further,takeamomenttofill out
andmailin theregistrationcard includedinthis
package.Doingsoentitlesyouto:
■
free,unlimitedtechnicalsupportvia email
■
free newsletters
■
newproductinformation
SinceMarkof theUnicorncan onlyprovide
customerserviceandtechnicalsupportto
registered users,pleasesendin thecardrightaway.
WHAT IS THE DIGITALTIMEPIECE?
Thinkof theDigitalTimepieceasthe synchroni-
zationhubforyourrecording studio.It provides
stable,centralizedsynchronizationservicesfor
mostanalog,digital audio,and video equipment
foundin today’srecordingstudio.Untilnow,
lockingtogetherADAT™,DA-88™,ProTools™,
wordclockaudiodevices,S/PDIFdevices,video
decks,SMPTEtimecodedevices,MIDIMachine
Control devicesandcomputershasbeendifficult
—if not impossible.TheDigitalTimepiece can
connect toallof thesetypes of devicesand
synchronizethemwithoneanother.
A computer is not required
You donotneeda computertouseaDigital
Timepiece.Essential settings areavailabledirectly
onthefrontpanel.Onceyouchooseanoperational
modewiththe TIMEBASEcontrols,the Digital
Timepiecewill generate or convertallformsof
synchronizationnecessaryto keepallconnected
devicessynchronizedwith oneanother.
Degrees of accuracy
Digital audiodevicesfoundintoday’sstudio
supportvaryingdegreesofaccuracywhenitcomes
tosynchronization.TheDigitalTimepiecesupplies
thebest possibleaccuracyforeachtype of device
thatitsupports.Mostdevicesfallintothefollowing
basiccategories of accuracy:
■
Sampleaccurate sync
■
Frame-accuratesyncwithphase lock
■
Frame-accuratesync withno phaselock
■
Frame-accuratetriggering

ABOUT THE DIGITAL TIMEPIECE
6
Synchronization firsts
TheDigitalTimepieceoffersseveralsynchroni-
zationfirsts.Forexample,youcannow
synchronizea stackofAlesisADAT™ recorders
witha stackof TascamDA-88™recorderswith
‘plug-and-play’easeandsample-accuratetiming.
TheDigitalTimepiecealso workswithother
devicesthatsupport theADAT andDA-88
proprietarysyncprotocols,suchas thePanasonic
MDA-1™,SONYPCM-800™andTascam
DA-38™.
The components of sync
TheDigitalTimepiecesuppliesall of thenecessary
componentsfor stable,sample-accuratesynchro-
nization:address(SMPTEtime codelocationand
audiosamplenumber),time base(wordclock),
andmachinecontrol(for transport andcueing).
You choosean externalsource —ortheDigital
Timepieceitself —as atime baseandaddress
master,and thenthe DigitalTimepiece
continuouslygenerates allothersynchronization
formats,locking togetherallconnecteddevices
withframe-accurate timing.Sample-accurate
timing is achieved with devices that allow it,such
asADATs andDA-88s.
The flexibility you need
TheDigitalTimepiece ismoreflexiblethanmost
synchronizersbecauseitallowsyouto choose
differentmastersourcesfortimebase,addressand
transport,as bestfitsyourstudiosetup.For
example,youcouldchoosehousesyncvideoasthe
mastertimebase,theDigital Timepieceasthe
address(timecode) master,and yourcomputer
softwareas thetransport master.
All standard digital audio sync formats
Digitalaudiosynchronizationformatssupported
includewordclock,Digidesign256x‘superclock’
andS/PDIF.Theseindustrystandardformatsallow
theDigitalTimepiecetosynchronizeawidevariety
of digitalaudiosystems,includingDigidesignPro
Tools™4.0,ProToolsProject™,stand-alonehard
diskrecorders,digital mixers,computer-based
digitalaudioworkstations,S/PDIFdevices(suchas
DAT recorders)andDigidesign’sAudiomedia™II
andIII cards.
Expensive add-ons are not needed
BecausetheDigitalTimepiecedirectly supports
third-partysynchronization formatslike
‘superclock’andADATSync,iteliminatestheneed
forexpensive synchronizationadd-onequipment
suchasDigidesign’s SMPTESlave Driver™,the
DigidesignVideoSlaveDriver™,Alesis BRC™,
Tascam SY-88™ synccardand others.TheDigital
Timepiecedramaticallyundercutsthecostand
setupoverheadof theseotherdeviceswhile
offeringmostof thesamefeaturesina compact,
efficient,singlerack-spaceunit.
All SMPTE time code formats
TheDigitalTimepiececan alsogenerateandslave
toall formsof SMPTEtimecode,includingLTC,
VITCandMTC(MIDITimeCode).AllSMPTE
frame formatsaresupportedwhengeneratingand
readingtimecode,including29.97 drop andnon-
drop forNTSCvideoapplications.TheseSMPTE
syncfeaturesallowtheDigitalTimepieceto
synchronizewith computers,analogtapedecks,
stand-aloneharddisk recorders,MIDIdevices,
andvirtuallyanythingthatcan eithergenerateor
slavetoSMPTE orMIDITimeCode.
MIDI Machine Control
TheDigitalTimepiecesupports MIDIMachine
Control(MMC)transport andrecordfunctions.
Thesefeatures allowyoutocontrolyourentirerig
fromasinglesource (suchasyourMMC-
compatiblecomputersoftware),eliminatingthe
needforexpensive,dedicatedhardwarecontrol
surfaceadd-onssuchastheAlesisBRC™and
Tascam RC-848™forbasicmachinecontroltasks.

ABOUT THE DIGITAL TIMEPIECE
7
SONY 9-pin machine control
TheDigitalTimepieceincludessupport forthe
SONY9-pinmachinecontrolformat.Youcan
connect aSONY9-pincompatible videodeck,
whichcan thenbe slavedto theDigitalTimepiece.
Thisallowsyou tocontrolthevideodeck,along
withall of yourothergear,fromyour favorite
MMC-compatiblecomputersoftwareorany
MMC-compatiblehardwarecontroller.
Conversely,theDigitalTimepiececanslave tothe
9-pinvideodeck.
Advanced video features
TheDigitalTimepieceprovidesmany other
essential videofeatures.The rearpanelhas two
BNCvideojacks (INand OUT)inadditiontoits
SONY9-pinconnector.Internally,the Digital
Timepiecehas abuilt-invideosync generator,
whichcan besynchronizedwiththeDigital
Timepiece’saudio phaselockengineorrun
independentlyof theDigitalTimepiece’s synchro-
nizationfeatures.TheVIDEOIN jackallowsthe
DigitalTimepiecetoslavetoany NTSCorPAL
video source,suchashousesyncvideoorVTR
output.TheVIDEOOUTjackcan display
whateverisbeingreceived onthe input,orit can
produceblackburst.Ineithercase,theDigital
Timepiececanoverlayuptotwelvelinesoftextand
informationonitsvideooutput signal,includinga
largeandsmallSMPTEtimecodeburn-in,status
information (e.g.the DigitalTimepiece’scurrent
samplerateoutput),MIDIsequencertriggered
streamerswith punch,andnumerouslinesof user-
programmed text(suchasclient andproject
names).Textlinescan be positionedverticallyas
desired.
44.1 and 48 kHz with pull up/down
TheDigitalTimepiecesupports 44.1kHzand
48kHzsamplingrates.Italsosupplies0.1%pull-up
andpull-downatbothrates,anessentialfeaturefor
thoseof youwho workwithfilm cuesthat have
been temporarilytransferredtovideoformusic
scoringoraudiopostproduction.Byusing apull-
down ratewhileworkingwithfilminvideoformat,
youcan easilyavoidsynchronization anddrift
problemsthatarisefromthe0.1%speeddifference
betweenthe filmtransferrateof 30fpsand the
NTSCvideoplaybackrateof 29.97fps.
Proprietary technology
TheDigitalTimepiecedeliverspristinesoundand
anextremely stable,high-resolutiondigital audio
timebasewithnodithering,rounding,orsoftware
delays.This levelof performanceismadepossible
by custom-designedVLSItechnology anda
proprietary high-frequencyphaseengine.
Fast lockup time
Dependingonthespecificscenario inwhichthe
Digital Timepieceisbeing operated,itslock-up
time canbeas fast asonesecond.Fastestlockup
timesareachievedbyslavingtheDigitalTimepiece
tohousesyncvideo(“blackburst”)orbyrunning
underitsown internal clock.Whenslavingthe
Digital TimepiecetoSMPTEorMIDItimecode
(withoutvideoas atimebase),lock uptime is
typically2-4seconds,dependingon theoverall
stability of theincomingtimecode.
Control track
Anew,proprietary Markof theUnicorn synchro-
nizationformat,called‘ControlTrack’,is supplied
via two8-pincircular DINsocketsontheDigital
Timepiece rear panel.Bymeans of high-resolution
sampleaddressinformation,ControlTrackcan
synchronizetwoDigital Timepieceswith sample-
accuratetiming.
Stand-alone and computer-based operation
TheDigitalTimepiececan be operatedin a
computer-based setuporasa stand-alone
synchronizer.Thefrontpanelsuppliesbuttonsand
statusLEDs formakingall of thenecessary basic
operationalsettings.Youcan choosetheoverall
operatingmode(calledthe‘timebase mode’),the
samplerate(44.1kHzor48kHz),sampleclock
pull-uporpull-down (0.1%),andSMPTEtime

ABOUT THE DIGITAL TIMEPIECE
8
codeformat(30,29.97,29.97drop,25and24).
Status LEDsarealso suppliedtoindicate
communication betweentheDigitalTimepiece
anddevicesconnectedtoit.AconvenientS/PDIF
THRUbuttonallowsyou toeasilybypass the
DigitalTimepiecewhentransferringS/PDIFaudio
from one device to another — without having to
swapcables.Thefrontpanelalsohasaquarterinch
phonejack foranAlesisLRC™orcompatible
controller.
The DigitalTimepiece rear panel
TheDigitalTimepiecerearpanelhasthreeinput/
outputpairsof BNCconnectorsforvideo,word
clock and Digidesign superclock.A pair of RCA
phonejacks supplyS/PDIFinputandoutput.
Otherrearpanel connectorsincludeapair of
standardADAT9-pinSyncIn andSyncOut
sockets,DA-8815-pinSyncInandSyncOut
sockets,a SONY 9-pinvideo syncjack,a pairof
quarter-inchphone jacksforSMPTE(LTC)input
andoutput,twopairsof MIDIINandOUT
sockets,anRS-422jack foroptionalconnection
directlyto aMacintoshcomputer,andtwo
additionalcircularDIN-8sockets fortheDigital
Timepiece’sproprietaryControlTrack protocol.
Convenient software included
TheDigitalTimepiece™shipswithMacintosh
console softwarethat provides accessto numerous
additionalfeatures.Forexample,theconsole
allowsyoutoprogram SMPTEtime codeoffsets
forindividual devicesconnectedtothe Digital
Timepiece,suchasasingleADATwithinachainof
ADATs.Youcanevenprogramindividualtrack
offsetsforADATsandDA-88s;trackoffsetscan be
specifiedas anumber of samples.The console
softwarealso letsyoucontrolthe Digital
Timepiece’svideographicsfeatures.

CHAPTER
9
2DegreesofAccuracy
BEFORE YOU GO ANY FURTHER…
Digital audiodevicesfoundintoday’sstudio
supportvaryingdegreesofaccuracywhenitcomes
tosynchronization.TheDigitalTimepiecesupplies
thebest possibleaccuracyforeachtype of device
thatitsupports.Hereis abrief overviewof several
basiccategories of accuracy to whichmostdigital
audiodevicesbelong,startingwith thehighest
(best).Afteryoulookthemover,think abouteach
deviceinyourstudioandthecategoryitbelongsto.
Doingsowillhelpyoumakebetterdecisionswhen
installingthe Digital Timepiece,whichsupports a
widerangeof synchronizationscenarios.
SAMPLE-ACCURATE SYNC
Whentwodevicesachievesample-accuratesync,
the master device and slave device are in
continuous,sample-accuratesynchronizationwith
eachother.Notonlyaretheirsampleclocks
continuouslyaligned(phase-locked),samplefor
sample,butthey alsolocateto—andstart playing
orrecordingon— exactlythe samesampleevery
time.Forexample,if themasterdevicecues to
samplenumber49,856,237inarecording,theslave
devicewillcuetoexactlythesamesample.
Resolutionis44.1or48thousandthsofasecond.A
slightbitof skew mightbeintroduceddueto
analogfilterdelays.Butif so,theskewwillbe
consistent,so itwillnot causephasing.
Anexampleof devicesthatsupport thislevel of
synchronizationis achainofADATtaperecorders
via theirproprietaryADATsyncprotocol.If you
record astereotrackpair fromoneADAT to
anotherintwo separaterecord passes,thestereo
imagewouldremaininperfectphase.TheDigital
TimepiecehastheabilitytodriveachainofADATs
atthislevel (sample-accuratelocatingwith
continuousphase-lock).Butevenmoresignifi-
cantly,theDigitalTimepiececan alsomakeastack
ofADATssynchronizewith astackof DA-88s
(whichalso support sample-accuratesync)atthis
level.TheDigital Timepieceisthefirst
synchronizertobeabletodothis.
FRAME-ACCURATE SYNC WITH PHASE-
LOCK
Whentwodevicesachieveframe-accuratesync
withphase-lock,masterandslavedeviceplayback
incontinuous phase-lock witheachother,sample
forsample,with nophasingor drifting over time.
However,thetimingresolutionatwhichthe
devices locate — and begin recording or playing
back— isequivalenttotheSMPTE timecode
frame ratebeingused (e.g.30framesper second).
Digidesign ProToolsis aclassicexampleof a
systemthatsynchronizesatthislevelof accuracy.
Whenslavingexternally,ProToolslocatesand
begins recordingor playingaccordingtoMIDI
TimeCode itreceives,whichhas a hasa quarter
frame resolutionof 30framesper secondtimes
four—orapproximatelya 120thof asecond(or
whatevertime codeframerateis beingused).
BecauseMTCsuffersfromgeneral MIDIdelays
andskewing,Pro Toolsand systemslikeitalso
employasoftwareaveragingschemewhichhelps
withaccuracyevenfurther.
Note,however,thatProTools—as aslave— also
requiresasampleclock(Digidesignreferstoitas
“superclock”or“slave clock”) to keep it phase-
locked withits masteronceitstarts.While
“superclock”maintainsphaselockatnormal
digitalaudiosamplerates(44.1 or48thousand
timesasecond),it doesnotprovidesingle-sample
locatingasdescribedin theprevioussection:it
simplykeepstheProToolssampleclockinphase

DEGREES OF ACCURACY
10
withthemasterdigital clockduringplayback or
recording,sampleforsample,toprevent phasing
(whichcausesdistortion)ordrifting(whichcauses
syncproblems).Butthehighestresolutionatwhich
Pro Tools canlocate— andbeginplayingor
recording— isone120th of a second(quarter-
frame resolution).If youtransferredastereotrack
pairin twoseparaterecordpasses intoProTools,
thestereoimagewouldnotbetransferredin
perfect phase.In otherwords,ProToolscannot
startatexactlythesamesampleasotherdigital
audiodevices,likeADATscan.(Futureversionsof
Pro Toolsmay providesampleaccurate synchroni-
zationcapability.)
FRAME-ACCURATE SYNC
Whentwodevicesachieveframe-accuratesync
withoutphaselock,masterand slaveremainin
syncwitheachother,buttheirdigital audioclocks
arenotkeptinphase.Instead,theystay in
continuoussyncvia time code,whichhas a
resolutionof athirtiethof asecond(oroneof the
otherstandardSMPTEtimecode frame rates).
Thisformofsynchronizationinevitablycausestwo
digitalaudiodevicestophasewithoneanotheras
theyplay,sincethe timingreference(30 frame per
secondtimecode)hassuchalowerresolutionthan
theirinternalsampleclocks.
Anexampleof thistypeof syncwouldbe astand-
aloneharddisk recorderslaved tothe Digital
TimepieceviaSMPTEtime codeonly,withno
wordclockconnectionbetweenthe devices.The
harddiskrecorderwouldreadtheincomingtime
codeandcontinuallyadjustitsdigitalaudiooutput
tostayin syncwiththetime code.
FRAME-ACCURATE TRIGGERING
Withframe-accuratetriggering,unlike anyof the
continuousformsof sync alreadydiscussed,the
masterdeviceonlytellsthe slavedevicewhereto
locate (ata specifictimecodelocation).Butwhen
theslavebeginsplayingorrecording,itrunsunder
itsown internal clock,inevitablydriftingoutof
syncwiththe master,givenenough time.Thetime
ittakesfordrifttobecomenoticeabledependson
thedevicesinvolvedandthe situationin which
theyarebeingused.Timingresolutionis
equivalenttoframeratebeingused(e.g.30 frames
persecond).
Mostdevicestodayuseoneof thecontinuous
formsofsyncdescribedearlier.Youprobablywon’t
encountera deviceof thistype inyour work with
theDigitalTimepiece.