The Spirit Guideto Digital Mixing

Cover.qxd 2/3/99 12:04 pm Page 1

SECTION 1:THE BASICS OF DIGITAL MIXING

A. Analogue & Digital - 3What�s the Difference?

B. Bits and Sample Rates 4C. The Question of Levels 5D. The Future 5

328 Focus: Audio Quality

SECTION 2: THE BENEFITSOF DIGITAL MIXING

A. Keep Music Digital 7B. Take Control Of Your Mix 7

328 Focus: Digital Interfaces, Use with PCI Cards, Snapshots Versus Dynamic Automation, E-Strip, Query System, Fader Laws

SECTION 3: WORDCLOCK

A. Choosing a Wordclock Master 10B. Where Does Timecode Fit In? 10

SECTION 4:FROM CONCEPT TO CD

A. Connecting to Multitrack Recorders 11B. Using the 328 with Analogue Recorders 11C. Using Tape and Group Outputs 12D. Recording Instruments 12E. Electric Guitars 12F. Recording Vocals 12G. Keyboards and Stereo Recording 13H. Mixing Down 13I. Using Effects 14J. Using Dynamics 14K. Using Automation 14L. Stereo Outputs 15

328 Focus: Mixer Maps, Linking Consoles

CO

NTE

NTS

2

THE SPIRIT GUIDE TO DIGITAL MIXING - CONTENTS

SECTION 5: 328 FAQ�s

Digital 328 FAQs 16

SECTION 6: DIGITAL TROUBLESHOOTING

Troubleshooting 18

Guide.qxd 02/03/1999 11:25 Page 2

molecules a series of pressure waves are created.As long as the frequency of these vibrations is with-in the range of human hearing (roughly 20 to20,000 cycles per second, depending on your age),we hear them as sound waves, and when theyreach our ear drum we hear the cymbal. But if wewant to do anything more with this sound � recordit, for example � we need to turn it into somethingthat we can manipulate more easily than pressurewaves in air.

In analogue audio circuits, sound waves are rep-resented by continuous electrical signals. At oneend of a typical audio chain, a microphone usesthe vibrations of air against its diaphragm to gener-ate a varying electrical current, and at the other aspeaker uses a varying electrical current to producevibrations in the air next to its cone.

Analogue electronics are always prone to noise �at the very least because the the random thermalmotion of electrons in components will producesome noise � though this can be minimisedthrough good circuit design, the use of high qualitycomponents, and good construction.

In digital equipment, the audio waveform is rep-resented by a series of numbers. An analogue sig-nal can be turned into digital form with an ana-logue-to-digital converter, which measures an ana-logue input voltage at regular intervals and gener-ates a sample (a number that represents theinstantaneous strength of the signal) each time. Aconverter that runs at a sampling rate of 44.1kHzsamples the signal 44,100 times per second, and ina well-designed converter the size of the samplesshould be in direct proportion to the input voltage.

A 16-bit converter can resolve 65,536 levels.A 20-bit converter can resolve 1,048,576 levels.A 24-bit converter can resolve 16,777,216 levels.

Because numbers can be described and copiedwith absolute precision, digital audio signals can bepassed from one machine to another, or from onepart of a digital mixer to another, with no change tothe sound. An analogue signal, on the other hand,cannot be passed through any component without

SEC

TIO

N1:

The B

asi

cs O

f D

igit

al

Mix

ing

3

THE BASICS OFDIGITAL MIXING

Welcome to the Spirit Digital Mixing Handbook �the essential guide to the world of digital mixing.Over the years it has become increasingly easy forthe solo musician, producer or small band toassemble a small studio, and with the advent ofaffordable digital technology, many of us now haveaccess to our own sophisticated recording facilitiescapable of producing release-quality material. Asthe central, and perhaps the most complex, singlepiece of equipment in the studio, the mixer hasalways been the most important item to get togrips with. Hence this guide, which helps youunderstand the principles and practice of digitalmixing. Enjoy!

A. Analogue & Digital �What�s The Difference?

The move from analogue to digital technology inthe world of audio is a revolutionary one, not justa small step. The technology is fundamentally dif-ferent, hence many of the the advantages of digitalover analogue. Although most practical aspects ofrecording and mixing are unchanged, some arenot, and it helps greatly to understand some ofthe principles of digital audio.

Whereas analogue electronics deal with contin-uously variable quantities (such as voltages andcurrents), digital electronics deal with discrete val-ues - numbers that can take only one of a prede-fined set of possibilities. Digital circuits do this bydealing with 1s and 0s, represented by the differ-ence between a switch being on or off, or a voltagebeing present or not.

This difference means that digital and analoguesystems represent sound in very different ways.What we perceive as sound is in fact a vibration inthe air. Hit a cymbal and it vibrates, transmittingthe movement to the air around it, and as thevibrations are passed on to more and more air

Guide.qxd 02/03/1999 11:25 Page 3

affecting it slightly. An analogy might be building amodel out of clay or out of Lego� bricks. You canmake copies of both, but even with the best cast-ing methods, you won�t be able to make a perfectcopy of the clay model. No matter how manytimes you make copies, or copies of copies of theLego � model, each can be exactly like the origi-nal.

One of the first areas of the audio to benefitfrom the introduction of digital technology wasrecording and playback equipment, and digitalrecorders have now almost entirely replaced ana-logue recorders in every application. Apart fromthe fact that a well-designed recorder with goodconverters offers very high audio quality, they offertwo distinct advantages. Firstly, the quality of digi-tal recordings remains unchanged even afterrepeated playback. Analogue tape recordings, onthe other hand, shows a progressive drop in quali-ty after repeated passes. Secondly, digital recorderscan use random-access rather than linear record-ing media, which allows them to play back record-ed material in many ways other than simply �asrecorded.� You can repeat sections (for choruses,for example), perform cut-and -paste editingoperations, and so on.

328 FOCUS: CONVERTERS

Converting between analogue and digital is one ofthe most critical stages of an audio signal path.Once a signal is in digital form, it�s fairly robust,but converting to and from analogue offers achance for audio quality to degrade significantly.In order to capture input signals as faithfully aspossible, analogue-to-digital converters shouldoffer high bit resolution � 16 or 18-bit convertersare looking rather outgunned in these days of 20and even 24-bit converters. The Spirit Digital 328has 24-bit 128-oversampling A-to-D and D-to-Aconverters, with considerably greater resolutionthan established media such as CD and DAT (16-bit), and allowing use with 24-bit systems such asnewer PC-based recording platforms.

At the output stage, the 328�s conversion is also24-bit with 128-times oversampling.

SEC

TIO

N1:

The B

asi

cs O

f D

igit

al

Mix

ing

4

B. Bits and Sample Rates

The two most important factors determining thequality of a digital audio system are sample ratesand bit resolution. A properly designed digitalrecording system can reproduce audio frequen-cies up to half of its sampling rate. So, in order tocover the full range of human hearing, a samplerate of 40kHz is required � hence the two mostcommon sample rates of 44.1kHz (the CD stan-dard) and 48kHz.

Bit resolution, on the other hand, determinesthe signal-to-noise ratio of the system - that is,how much difference there is between its quietestand loudest output. You may have heard that digi-tal systems can achieve a performance of 6dB ofsignal-to-noise per bit, so a 16-bit system (CD orDAT, for example) manages 96dB. A 20-bit systemcan in theory manage 120dB, though in higherresolution systems it becomes harder and harderto achieve theoretical performance.

328 FOCUS: USING DITHER

When you take a 24-bit audio signal down to 16-bit resolution, you inevitably lose quality. Whereasthe 24-bit signal could have a signal-to-noise ratioof 144dB, the 16-bit version of it has a signal-to-noise ratio of 96dB. The Spirit Digital 328�s stereodigital outputs, both AES/EBU amd SPDIF, use atechnique called dithering to preserve as muchquality as possible when going down to lower-res-olution media, such as DAT, which have poorersignal-to-noise performance than the mixer�sinternal signal path. Dithering involves adding asmall amount of noise to the 24-bit signal at justabout the theoretical noise floor of a 16-bit signal.Odd though it may sound, this trick means thatyou can hear low level sounds (reverb tails, forexample) well down below the noise floor, and the16-bit signal actually achieves a dynamic range ofaround 115dB. This improvement is audible nomatter what DAT player the recording is played on- it does not require any special decoding.

Guide.qxd 02/03/1999 11:25 Page 4

SEC

TIO

N 1

: Th

e B

asi

cs O

f D

igit

al

Mix

ing

5

C. The Question Of Levels

In the world of digital recording, you have to treatlevels with a little more respect than in analoguesystems in order to avoid distortion. This isbecause of the very different ways in which ana-logue abd digital systems work.

We know distortion when we hear it, but howdoes it arise? Put simply, distortion is an unwant-ed change in the audio waveform, usually causedby the clipping of the audio waveform. As youcrank up input levels, you reach a point where thesystem cannot recreate at the output the extremepeaks and troughs at the input � and that�s distor-tion. In analogue circuits distortion tends to comeon gradually, increasing in severity as input levelsare increased. Because it can sound good to thehuman ear, some types of analogue distortionhave long been exploited in the studio � to warmup drum sounds by recording �hot� to tape, byusing tape saturation characteristics. So, althoughthe point at which distortion begins can usually bequite well identified, you can generally �push� thislevel a little without ruining your recording.

Digital electronics, on the other hand, deal witha precisely defined range of levels. As you increasethe level going into an analogue-to-digital convert-er, the numbers coming out get bigger and bigger� until you run out of resolution at the convert-er�s maximum input level, and you have the sud-den onset of distortion. For reasons which are tootedious to go into, digital distortion doesn�t soundat all pleasant, and it�s therefore very important toavoid exceeding maximum levels.

Metering also works differently. In analoguemixers and recorders, equipment is designed tooperate at various operating levels, such as+4dBV (most �professional equipment) or -10dBU, and the relationship between 0dB onmeters and the point at which distortion starts isnot fixed. Also, because distortion comes in gradu-ally, you can almost always get away with pushingyour meters some way into the red.

In a digital system, metering is relative to0dBFS, which is the point at which the system hasrun out of numbers and you cannot go any higherwithout creating distortion. There is no LED on abargraph meter above this, because there isn�tanywhere else to go. Because distortion occurs assoon as you exceed these levels, whenever you�resetting levels bear in mind that even peaks shouldnot light the red LEDs at the top of the 328�smeters, though this might feel right if you�re usedto working with analogue mixers.

D. The Future

Because digital audio technology rides benefitsfrom progress in the very fast moving area ofcomputer technology, things are always movingahead. From 16 bits and 44.1kHz, we�ve movedon to a point where 20 and 24-bit recorders are inuse, some with 96kHz sampling. The need tomove greater amounts of data around means thatnew interface standards will appear. Firewire(IEEE1394) is already establishing itself as a use-ful transfer protocol in digital video, though it maysoon also be used in audio. Another trend that isis likely to continue is the use of cheap, powerfulconsumer or business computers to run increas-ingly powerful audio software, software that cantake over more functions previously performed bydedicated hardware.

Guide.qxd 02/03/1999 11:25 Page 5

SEC

TIO

N1:

The B

asi

cs O

f D

igit

al

Mix

ing

6

FIG 1.1

Waveforms as represented in analogue and digitalsystems

FIG 1.2

Distortion in analogue and digital systems.

328 FOCUS: AUDIO QUALITY

Spirit has earned a reputation over the years forvery high audio quality at affordable prices, andthe Digital 328 carries on that tradition. As well asits high-quality converters � see �Using Dither�on this page � the Digital 328 also offers very highresolution (56 bits) in its internal processing. Thisis important because everything that happensinside a digital mixer � combining two signals,changing a level, deriving a feed to an external Auxor internal FX send � involve making calculations,and these calculations must be carried out with ashigh a degree of precision as possible. Each time acalculation is performed, you need a longerwordlength to store the result without �roundingoff � the result, and thereby losing precision thatcarries valuable information about the sound. So,although the Digital 328 starts with 24-bit num-bers at one end, and ends up with 24-bit numbersat the other, using 56-bit precision for the pro-cessing along the way means that repeated pro-cessing steps can be applied without adding noiseor distortion.

Guide.qxd 02/03/1999 11:25 Page 6

Although on the inside the way that a digital mixerworks is quite different to the way that an ana-logue mixer works, they do the same job � com-bining your various audio sources, mixing andcontrolling them on their way to whatever outputsyou need. In some applications, the advantages ofa digital mixer are directly connected with the waythat it works inside, in other applications theadvantages are less obviously connected to its digi-tal nature.

A. Keep Music Digital

In a typical audio chain, the sound of an instru-ment or voice may pass through a mixer severaltimes before it makes it way to a pair of speakersor headphones � once on its way to a digitalrecorder, then back through the mixer again dur-ing mixing, out and back in via an effects loop,and so on. Now that so much of the equipmentaround the mixer is digital, if the mixer offers onlyan analogue signal path then the audio may gothrough many steps of conversion between ana-logue and digital, losing a little quality each time.With a digital mixer, however, you can transferaudio to and from your digital multitrack, and toand from digital effects units, entirely in the digi-tal domain. Many synths and samplers now offerdigital outputs, and a digital mixer can also addeffects, and perform dynamic processing, all with-in going back out to analogue. By cutting outunnecesary conversion steps, your recordings canstay in the digital domain from the moment theycome into the desk to the moment they come outof a CD player, ensuring the best possible quality.

B. Take Control Of Your Mix

One of the basic features of analogue mixer con-struction is that all of the hardware controls arealso audio components. When you move a chan-nel fader, you�re changing the resistance in an

SEC

TIO

N2:

The B

enefi

ts O

f D

igit

al

Mix

ing

7

audio component in the signal path. When youmove an EQ knob, you�re tweaking a variable potthat is part of a channel strip�s EQ circuitry. Witha digital mixer things work completely differently.The audio processing takes place in chips that arenot directly linked to any controls, which presentsa great opportunity for designers to create newinterfaces for their products, freed from the slav-ery of one-control-per-function. Because theaudio handling and control aspects of the desksare now separate, each can be made to work aswell as possible, rather than there being any com-promise. And contrary to popular belief, there�sno need for a digital mixer to behave like a com-puter, relying on menu-driven interfaces ratherthan intuitive controls.

Although it would be possible to create a digitalmixer with a control for every parameter, such adesign would be much more expensive than onein which fewer assignable controls are used. TheSpirit Digital 328, for example, uses clearly laid-out assignable controls, and behaves like a tradi-tional mixer rather than a computer. All majordesk operations can be achieved with a few simpleand intuitive control inputs, and you hardly everneed to refer to the LCD screen. Nonetheless, youhave the flexibility that comes with controls thatcan change at the touch of a button � one minuteyou�re adjusting levels, the next you're sendingout MIDI controller messages. And if you want togo beyond the 328�s own control surface, you canuse any major sequencer program running onany computer platform to map the Spirit 328 con-trols to on-screen graphic controls.

Because a layer of software sits between thephysical controls and the audio processing of adigital mixer, it is relatively easy to add advancedfeatures such as automation and remote MIDIoperation, all of which gives you more mixingcontrol. The two types of automation that you findon digital mixers are �snapshots� � which store allthe desk�s audio settings and can be recalled atthe touch of a button or against timecode � anddynamic automation, in which you can recordand playback any and all of the fader and othercontrol changes that you make.

THE BENEFITS OFDIGITAL MIXING

Guide.qxd 02/03/1999 11:25 Page 7

SEC

TIO

N2:

The B

enefi

ts O

f D

igit

al

Mix

ing

8

328 FOCUS: DIGITAL INTERFACES

The Spirit Digital 328 has both stereo and multi-channel digital interfaces, enabling you to connecta wide range of digital equipment to its inputs andoutputs. There are two sets of 8-channel ins andouts, using on-board ADAT optical and TDIF(Tascam) format interfaces, for group/tape out-puts and tape returns. Both AES/EBU and SPDIFinterfaces are also supported, allowing FX sendsand returns, the stereo mix output, and 2-trackreturns (for DAT machines or other stereo mas-tering media) to be carried by digital as well asanalogue connections.

328 FOCUS: USE WITH PCI CARDS

More and more studios, especially small personalfacilities, exploit the power of PCI cards installedin personal computers to provide cost-effective yethigh quality and sophisticated recording and pro-duction. A fairly standard PC or Mac, equippedwith a suitable £500 card, could offer multi-trackrandom access digital recording and playback,replacing a studio multitrack tape recorder. Withthe right card and software, you could add sampleplayback and sophisticated effects, putting manyof a studio�s electronic instruments inside thecomputer. This technology has become very cheapbecause of the falling price and easy availability ofchips and other components. Also, the adoption ofmulti-channel digital interfaces like the ADAT opti-cal system means that the ability to handle multi-ple channels of audio input and output can beeasily included on these cards, but a good mixerfront end is essential to exploit this kind of tech-nology to the full. The Digital 328 interfaces easilyand effectively with these cards and the systemsthat they are intended to support. A typical setupmight involve a Mac or PC with a Korg 1212 card,running Steinberg�s Cubase Audio VST software.Using the ADAT optical connections, the 328�seight group outputs feed the Korg 1212�s eightADAT inputs, and the �tape� returns go from com-puter to the 328 also via an ADAT optical inter-face. (If the computer is fast enough to allow

more than eight tracks of playback, the internalpre-mixing abilities of Cubase Audio can be usedto pre-mix several tracks to each of the eight avail-able output busses).

328 FOCUS - SNAPSHOTS VERSUSDYNAMIC AUTOMATION

Depending on the nature of a project, either the328�s snapshot or dynamic automation, or a mix-ture of both, may be most appropriate. For exam-ple, you might use snapshots to store basic mixersetups for several different songs that you areworking in, or for sessions for different artists,and then use dynamic automation for mixdown. Ifyou�re working to picture, snapshots can be par-ticularly useful. By recalling snapshots againsttimecode, changes in the mix can be easily madeto happen in precise sync with picture edits, and ifthe picture is re-cut, you simply need to changethe timecode values for the audio cues ratherthan rebuild a whole dynamic mix.

328 FOCUS: E-STRIP

The key to the Spirit Digital 328�s user interface isthe E-strip, a row of 16 rotary encoders above the16 motorised channel faders. Its primary functionis to operate exactly like a regular analogue mixerchannel, only rotated through 90 degrees, with thefamiliar 3-band EQ controls, four aux sends, twoeffects sends (to the two internal processors), andpan control. As well as being familiar, it�s easy touse: just hit the select button for the channel youwant, and the E-strip�s continuous rotary con-trollers put all the channel EQ, aux and pan facili-ties at your fingertips. A ring of LEDs around eachcontroller shows you the current setting for eachparameter. Channel features that are used lessoften, such as bus routing and phase reverse, arecontrolled via the master section, while the chan-nel�s analogue controls (100Hz high-pass filterand channel input gain) are found at the top ofthe front panel. The second function of the E-stripis to give simultaneous control of a set of 16 Level,Pan, or send controls for FX1 or 2, or Aux 1 to 4,for channels 1-16 or 17-32.

Guide.qxd 02/03/1999 11:25 Page 8

SEC

TIO

N2:

The B

enefi

ts O

f D

igit

al

Mix

ing

9

328 FOCUS: QUERY SYSTEMBecause the Spirit Digital 328 is a very flexible andfully-featured mixer, it�s simply not possible toshow all desk parameters simultaneously in orderto let you see how everything is routed or switched� that would produce a very confusing front panel,whereas the 328 design approach has been to cre-ate an uncluttered, easy-to-navigate interface. Onan analogue desk, you can quite easily check thedesk state �at a glance�, because there�s one con-trol per function � the trade-off is that you can endup with a huge number of controls on a frontpanel. The idea behind the query system on theSpirit Digital 328 is that it allows the user to ask asimple question and get a simple answer. The key isthat it uses the same intuitive means to check rout-ing as to make the routing assignments. To routechannels 3 and 4 to the stereo mix bus, for exam-ple, you do the following: Press the Select buttonfor channel 3, and see if the Route To Mix button islit. If not, then press the Route To Mix button toassign the channel to the mix bus; the button lightsup green to indicate that this has been done. Nowpress the select button for Channel 4, and repeatthe procedure. If you now want to check whichchannels are routed to the Mix bus, press and holdthe Route To Mix button; all channels which arerouted to the mix will be shown by their illumiin-taed Select buttons, while all channels that are notwill remain dimmed. With this one button push,you can check all 32 mono channels and tapereturns, both stereo inputs, eight groups and bothFX returns � and to make routing assignments eas-ier still, you can add more channels to those routedto the mix by hitting their dimmed Select buttonswhile you keep the Route To Mix button held down.

328 FOCUS: FADER LAWSAnother aspect of a digital mixer�s user interface that can be more easily modified or controlled than

on an analogue console is the fader laws � that is, exactly how your control inputs translate into anaudible effect in the signal. For example, on thechannel, master and group faders of most mixers� including the 328 � movements in the top halfof the fader produce less audible change in levelthan the same movement lower down, whichmeans that in the crucial area around 0dB gain,where you effectively do most of your mixing, youhave most control.

On the 328, the response of all controls is care-fully tailored to suit the parameter you are chang-ing. When you adjust the internal FX sends, forexample, you find that the first 180° of travel ofthe rotary encoders takes you from -fdB to -18dB,which is quite a jump, whereas the last 180° givesyou a much more sensitive control over the tran-sition from here to 0dB - appropriate to an effectsend, where you almost invariably want to max-imise the level going to the effect, to give the bestpossible signal-to-noise ratio at the other end.Although rotary encoders, as used on the 328 andmany other digital mixers, are essentially lineardevices � part of their value as controllers is thatthey have no centre position � part of the secret togood design in a digital mixer�s user interface ismakng the controllers feel right.

Another respect in which the �feel� of the con-trols has been carefully looked at is the low andhigh EQ bands behave when you turn the Shapeknob to take the EQ from parametric to shelvingmode. When you do this, you�ll find that thesound changes smoothly, and the centre/cutofffrequency as displayed on the mixer�s LCD, doesnot change � this bends the rules on how the cut-off frequency of a shelving filter is defined, but itfeels right. And since you should mix with yourears, not by looking at a display, we think theworld of audio will forgive us�

FIG 2.1

E-Strip

Guide.qxd 02/03/1999 11:25 Page 9

Wordclock is the glue at the heart of digital sys-tems, and understanding a little about it will avoidthe frustration of not being able to solve somebasic and simple problems. Symptoms of word-clock-related problems include unwanted pops orclicks, and a metallic edge or other distortion ondigital sources.

In any situation where several digital audiodevices are connected via their digital rather thantheir analogue audio connections, all the devicesmust be wordclock synchronised to avoid datatransfer problems. This means not only that thedifferent devices send and receive their data at thesame sample rate � 48kHz, for example � butthat their internal clocks run precisely in sync.This ensures that all units send, receive andprocess their data streams in a precisely simulta-neous manner, avoiding a major source of distor-tion and poor audio quality. To understand howthis distortion arises, consider a simple situationin which a DAT recorder�s digital output feeds amixer's digital input. They are both using a44.1kHz sampling rate, but their clocks are notsynchronised. The mixer�s input should have44,100 �slots� every second that have to be filledby samples, and the DAT recorder should be send-ing it 44,100 samples every second. But if there isonly a slight drift in one of the clocks, some ofthose samples will be missed or will �jump� aplace, and that means distortion.

So, in any system that sends digital audiobetween several different devices, one unit shouldbe the wordclock �master�, and the others shouldbe �slaves�. Setting this up is usually very easy, asthe slaves can generally derive their wordclocktiming from their digital audio inputs � SPDIF,AES/EBU, ADAT or whatever. Wordclock can alsobe carried via a separate connection. In eithercase, the wordclock signal is present whetheraudio is sent or not.

SEC

TIO

N3:

Word

clock

10

WORDCLOCK A. Choosing a Wordclock Master

If you are using several digital connections atonce, you may not be left with much choice as towhich device should be your wordclock master. If,for example, you are using a sampler with a digi-tal output, you may find that it does not have anyfacility to slave to an external wordclock input,and must therefore be the wordclock master. Onthe other hand, any digital recorder in the systemshould be the master, though some recorders arequite happy to slave to external wordclock. As arule, PCI cards installed in computers behave bestwhen they are wordclock masters rather thanslave. Trial and error will tell you whichmaster/slave combinations works best.

B. Where Does Timecode Fit In?

Timecode synchronisation is different to word-clock synchronisation, but equally important inanother way. While wordclock enables digitalaudio to be transferred without problems, bykeeping the various audio inputs and outputs run-ning at the same frequency, timecode enablesrecording and playback devices to run in syncwith one another, and with sequencers and deskautomation. Timecode is a signal that carries aregular series of absolute time values(hrs:mins:secs:frames). There are different framerates (hinting at timecode�s origins in the need fora means to synchronise film equipment), of 24,25, 30 (drop and non-drop) frames per second.As in wordclock, one device is defined as the mas-ter, and its timecode keeps every other recorderrunning along in synchronisation. The two timingsystems are quite independent, and a recorderthat is the wordclock master in a system could bethe timecode slave of another device (the 328, forexample, which can generate all timecode framerates).

Guide.qxd 02/03/1999 11:25 Page 10

SEC

TIO

N4:

From

Conce

pt

To C

D

11

FROM CONCEPT TO CDnections are made, hit the Menu button, scrolldown to Tape Machine Setup, and select �TascamDA88/38�. You will now be asked to choose a time-code source. Choose LTC, unless there�s somereason why you need to use MIDI timecode. Nowgo the Clock Source Select menu, and choose�Intenal 48kHz�. Now you�re ready to roll�

In another setup, based around a computerrather than tape machines, you might use aDigidesign ProTools system with its ADAT BridgeI/O, making a 16-channel connection using twosets of ADAT optical connections. With a systemlike ProTools, the 328�s powerful mixing front endis a perfect complement to advanced and veryhigh-quality digital recording and editing facilities.

B. Using The 328 With AnalogueRecorders

You can connect an analogue multitrack recorderto the 328 with optional breakout boxes connect-ed to the TDIF ports. Each breakout box gives you8 analogue inputs and outputs, so with two break-out boxes you can connect a 16-track analoguerecorder, such as a Fostex G16, to the 328. In thiscase, you could remote control the recorder fromthe 328, and use snapshot automation slave totimecode from the recorder.

The small studio probably benefits more than anyother area from the advent of digital mixing. Thissection takes a look at typical small studio setups,and how to set about recording a typical track onyour 328-based studio.

A. Connecting to MultitrackRecorders

Before you can record anything, you need to getconnected to your multitrack recorder. Straightout of the box, the Spirit Digital 328 is ready toconnect directly to a wide range of digitalrecorders � 16 channels of multitrack outputsand returns are available, in two 8-channel blockscorresponding to channels 17-24 and 25-32. Eachblock has both TDIF and ADAT optical interfaces. See below for a typical setup, in which two TascamDA88 recorders provide 16 channels of record andplayback. Audio connections are made via TDIF,and the recorders are slaved to the desk�s word-clock. The tape transports are remote controlledfrom the 328 via MIDI � once the physical con-

FIG 4.1

Connection Diagram

Guide.qxd 02/03/1999 11:25 Page 11

SEC

TIO

N4:

From

Conce

pt

To C

D

12

samples into your sampler, or selecting the rightkeyboard sounds.

E. Electric Guitars

You should�nt plug electric guitars or bass guitarsstraight into a mixer. If you want to record a cleanguitar sound, then use a DI box to get a good levelinto the desk. Some DI boxes require phantompower, and should be connected to the channel�sXLR inputs (make sure the 328�s +48V phantompower is switched on). If it�s a distorted guitarsound you�re after, you can either mic up the gui-tar cabinet, pointing a mic right at the speakercone, or use a multi-effects processor. If you haveenough tracks to take advantage of it, you canrecord the multi-effects in stereo � the processorsalmost invariably have stereo outputs, and flang-ing, chorus and delay efects sound better instereo. See below for tips on using stereo chan-nels.

Try applying compression while recording gui-tar tracks to keep levels under control. Using thecompressor/gate algorithm on the 328 will allowyou to gate out the unwanted buzz and hum thattends to come with distorted guitar settings, andwhich you�ll only have to remove before mixinganyway.

F. Recording Vocals

The Spirit Digital 328 has high-quality mic pre-amps on channels 1-16, which are vital to record-ing good vocals. A good condensor mic will gener-ally give the best results, as they are more sensi-tive and revealing than dynamic mics. Condensorsrequire +48V phantom power, which the 328 canprovide via the XLR channel input sockets. If youhave the luxury of a choice of mics, be openminded about what to use � try them all beforedeciding what to use.

Set your mic up around 9 inches from yoursinger, with a pop shield (nothing really worksbetter than the old stocking-and-coathanger trick)between singer and mic to avoid problems with

C. Using Tape & Group Outputs

There are two approaches to using outputs totape. The first is to use your mixer�s group facili-ties to combine several channels together forrecording � the outputs for the eight groupsappear at the 8 TRK A outputs on TDIF and ADAToptical outputs. The second is to route channelsdirectly to tape. (In an analogue mixer, this hasthe advantage of a cleaner signal path, though in adigital mixer like the 328, you can route throughgroups without adding any noise or distortion.)

The first approach is suitable for recording sev-eral instruments together onto one or two tracks� a multi-miked drum kit, for example. Thismakes sense when you don�t have enough tracksto record every instrument to its own track. Thesecond approach is suitable where you need torecord more than eight tracks at once, perhaps ina live situation, and is simpler. Channel 1 alwaysfeeds track 1, channel 2 feeds track 2, and so onup to 16.

When you play back your recorded tracks, theycome in on channels 17-32. Although they�recalled Tape Return channels, they have exactly thesame facilities as channels 1-16.

D. Recording Instruments

Let�s assume that you want to put together a trackthat uses live vocals and guitar with programmedkeyboards and drums. You�ve programmed thebasic song structure on your sequencer, andyou�re using two DA88s as above for your record-ing medium.

The first thing you�ll need is a guide for every-one to play along to. As you already have drumsand keyboards programmed, you could run yoursequencer in sync with the tape transports as yourecord vocals, guitar and percussion. Alternatively,you could record a rough stereo mix of keyboardsand drums to two tape tracks, which means thatin future sessions you can get your guide tracksup without having to worry about loading the right

Guide.qxd 02/03/1999 11:25 Page 12

�plosive� sounds. Remember that making yoursinger as comfortable as possible will help to get abetter vocal performance, so be sensitive to theirneeds. You may find that the 100Hz high-pass fil-ter is useful to cut out rumble, though this is gen-erally more of a problem live than in the studio.Avoid EQ�ing vocals when recording, as it will tendto make them sound artificial, and you�ll regret itlater.

Set up a vocal monitor mix on headphonesusing one of the Aux sends � a quick way to dothis for, say, Aux 1, is to hit the Aux 1 button abovethe E-strip, so that the 16 rotary controls let youset Aux 1 send levels for channels 1-16, then hitAux 1 again to set the send levels for channels 17-32.

Because vocal levels tend to vary widely, it�sadvisable to use compression to level things out.Try using one of the internal dynamics processors,using the compressor algorithm (with a 10msattack, around half a second release, and ratio of4:1 and 8:1). Alternatively you could use afavourite outboard compressor, plugged into thechannel insert point.

G. Keyboards and StereoRecording

Although one of the advantages of using MIDI isthat you can record keyboards and samplers on asequencer, and play them �as live� into the mixwithout ever going down to tape or disk, you mayinstead want to record keyboard parts to multi-track. One reason is that it forces you to committo a certain sound or version, rather than leaveeverything in a half-finished state. Also, it meansthat if you plan to take your project from your stu-dio into a larger room for final mixing, you cantake ADAT or DA88 tapes, or a computer with allyour tracks recorded on HD, rather than a rack ofkeyboards.

But whether you do this, or leave the electronicinstruments to be played via MIDI at mixdown,you�ll want to use stereo inputs on the Digital 328

SEC

TIO

N4:

From

Conce

pt

To C

D

13

to get the benefit of all those stereo samples andstereo outputs. There are two stereo input chan-nels on the 328, with all the the EQ, Aux and FXfacilities of the mono channels. You can go direct-ly into these via stereo digital interfaces � eitherSPDIF or AES/EBU � or use analogue inputs as onthe mono channels. Remember that if you use thedigital inputs you should take care with word-clock, as an unsynced audio source will show dis-tortion of some kind, which will negate the bene-fits of using the digital inputs. If you have morethan two stereo sources, you can link adjacentmono channels to behave as another stereo chan-nel, with all EQ and Aux settings shared betweenchannels.

H. Mixing Down

When you�ve recorded everything you need foryour track, it�s time to mix everything down to astereo master recording prior to CD mastering, orplayback on any other stereo medium. Whetheryou�re using a sequencer or not, the 328�sautomation features make this much easier thanwith a non-automated desk.

The first step when preparing your mix is to setthe desk in a neutral state. For all tape returns,check that EQ is off, and all sends are set to 0. Ifyou are working in a MIDI-based studio, you mayhave used EQ and effects quite heavily on some ofthe synths and samplers, and now is the time torethink what is essential to the sound, and what iscluttering up the mix and should be removedbefore proceeding. Mute all inputs that aren�tbeing used, and for any analogue inputs, set thegain as high as possible without clipping � use thechannel metering to check this. You can now startworking up a mix.

Begin with the basics of the track � probablybass and drums. Set their relative levels so thatneither dominates the other, and keep them inthe centre of the stereo image. Use the eight inter-nal groups to group together instruments that youwill want to fade up and down together, such as

Guide.qxd 02/03/1999 11:25 Page 13

SEC

TIO

N4:

From

Conce

pt

To C

D

14

backing vocal parts, drum and percussion parts,string arrangements and so on.

Try using EQ to boost each instrument in aslightly different band, preferably the frequencyrange that carries most of the character of thatinstrument. This will help to distinguish themfrom one another, and make them sit apart in themix. Using a little reverb on each channel tends tobring everything back together, creating theimpression that the various sounds are all playingin the same acoustic space.

I. Using Effects

With two Lexicon effects processors inside the328, it�s easy to add a wide range of high qualitystudio effects. As well as a full selection of classicstudio reverb and delay-based algorithms, eachprocessor has more distinctive off-the-wall effectssuch as Resonant that are worth trying out. Whensetting up your effects mix, remember that you�llget the best signal-to-noise ratio, and therefore themost professional sounding mix, by keeping thesend levels high and the return levels low.

You can also use external processors, using oneof the Aux sends to take a signal to the processor,and bring the effect back on stereo inputs orlinked stereo channels. If your processor has digi-tal inputs and outputs, by assigning an Aux sendand stereo return to the 328�s stereo digital inputsand outputs, you can keep the whole effectsend/return loop in the digital domain.

J. Using Dynamics

As well as the two internal Lexicons, the 328 alsohas two internal digital dynamics processors.These let you apply compression and limitingwhile track-laying, to avoid clipping and distortonand get a good level down to your recording medi-um. Gating any mic�d sources will keep unwantedbackground noise out of your mix. Because youcan select the source for each dynamics processor(the source that determines gain change) inde-pendently of the destination (the channel or chan-

nels whose levels are changed), you can get cre-ative with the dynamics section. Try using a gate,keyed from a rhythmic sound such as a hi-hat, tomodulate the volume of a continuous sound suchas a keyboard pad.

K. Using Automation

Once you have set up a basic mix � instrumentssitting in the right place in the mix, the righteffects balance � think about where you want tochange this through the mix. By using snapshotautomation, running against timecode, you canchange fader levels, effects and aux sends, EQ andbus routing, wherever you need. Store the varia-tions on the basic mix in different snapshot loca-tions, and give them names if you like. Now givethe snapshots timecode locations that correspondto the point in the song where you want thechange to happen. (Stop the song at whateverpoint the change needs to happen, such as whena solo starts, or an instrument drops out and youwant to mute its track, and give the snapshot thistimecode value.) If you�re anticipating a solo, setthe snapshot to change just a little ahead of thefirst note that it will affect, in order that you don�tcut off the start of anything � and if you�re mutingafter an instrument has finished playing, be care-ful not to mute before the last note has died awaycompletely.

If you�re using a MIDI sequencer, then you canuse dynamic automation and moving faders tomix in a different way. If you are using MIDI toplay instruments as well, and you have a multi-port MIDI inteface, it�s good practice to dedicateone MIDI port to the automation data rather thanmix note and automation data. By recording pro-gressive fader and other changes, you can set upperfect fades at the end of your song, or to takeinstrument parts up and down. Remember thatyou can also automate EQ and other changes � infact, almost every parameter on the desk, apartfrom the analogue controls, such as control roomlevels, can be automated and therefore used tocreative effect in a mix.

Guide.qxd 02/03/1999 11:25 Page 14

SEC

TIO

N4:

From

Conce

pt

To C

D

15

Use automation to give your track the dynamicsthat it needs. Try having some instruments that sitback in the mix for much of the time, then sit up� higher volume, less effect � at key moments.But remember above all that it�s your track, andyou�re the best judge of how it should sound. Adigital mixer such as the 328 gives you an amaz-ing degree of production power, and it�s up to youto decide how to use it.

L. Stereo Outputs

When you master your recording, you can recordto both digital and analogue media � balancedanalogue outputs are available alongside unbal-anced phonos. If you�re using the digital outputsto DAT, MD or an MO recorder, use the highestresolution avaialble to you. If your media allows it,make your recording at 20 or 24 bits rather than16 � both the SPDIF and AES/EBU outputs can beset to run at any of these wordlengths.

328 FOCUS: MIXER MAPS

In a studio based around a computer and PCIcard, you can extend the integration betweensequencer and the 328 beyond audio. CubaseAudio VST, Emagic Logic, and Cakewalk all allowcustom mixer maps (on-screen MIDI faders) tocontrol and be controlled by the 328�s dynamicautomation. By integrating sequencing and mixingto this degree, you have still more flexibility inyour writing and mixing techniques. Mixer mapscan be downloaded free of charge from the Spiritweb site.

328 FOCUS: LINKING CONSOLES

If you�re working on a project that grows andgrows, you can cascade two 328s via a special digi-tal link, to create what is in effect a single auto-mated digital mixer with 32 moving faders and 84inputs on mixdown.

Guide.qxd 02/03/1999 11:25 Page 15

How does the reliability of the Digital 328 com-pare to an analogue console? Traditionally, ana-logue consoles have been constructed using a sin-gle printed circuit board for each channel, plusone board for each function in the master section.Each circuit board uses conventional electroniccomponents, and the boards are linked togetherby ribbon cables. The Spirit Digital 328, on theother hand, uses 'surface mount' technology andhigh density printed circuit boards. Surface-mount technology has been widely used in thecomputer industry, improving reliability andspeed.

IS THE OPERATING SYSTEM UPGRADEABLE?

Yes: newer versions of the 328 Operating Systemwill be made available through the Digital 328 website (www.digital328.com), or as an upgrade kitfrom Spirit distributors. These updates will beaccessible as soon as new versions are released,and (internet updates only) available at any timeof the day. All software upgrades are provided freeof charge by Spirit.

WHAT DIGITAL INPUTS AND OUTPUTSARE FITTED AS STANDARD?

* 2x8 track inputs Alesis ADAT optical format* 2x8 track outputs Alesis ADAT optical format* 2x8 track inputs TDIF format* 2x8 track outputs TDIF format* 1x8 track variable outputs Alesis ADAT optical

format* 1 AES input on XLR* 1 AES output on XLR* 1 S/PDIF input on RCA* 1 S/PDIF output on RCA* 1 MIDI In 1 MIDI Out 1 MIDI Thru* Wordclock input on BNC* Wordclock output on BNC (TTL level)* 1 SMPTE input on quarter-inch jack* Sony 9 pin for Machine Control ( RS-422 )* Cascade Port on 26 way HD D-type connector

HOW MANY EXTERNAL DIGITALRECORDERS CAN BE USED AT ONCE?

Two. The Spirit Digital 328 has two Alesis Opticaland two Tascam TDIF interfaces located on theback panel, one of each for each set of eight tapeinputs (17-24, 25-32). The front panel includestransport controls, with locator points, and theability to arm (and indicate arming) any of the 16tracks for recording. If two 328s are linked viathe cascade facility, up to four recorders (with 32tape channels) can be used.

ARE THERE ANY DIGITAL AUX SENDS?

Yes. A third Alesis ADAT format Optical output(labelled Aux) is located on the back panel. Thesource for the eight channels of this Aux OpticalOutput can be set to come from the AUX bus, FXbus, MIX output or Group buses. Companies suchas Alesis and TC Electronics are already designingeffects units with Optical In/Out, as well as stan-dard quarter-inch jacks.

CAN A CD OR DAT MACHINE BE CON-NECTED DIGITALLY?

Yes. Most professional, and some consumer, audioDAT and CD-R machines include stereo digitalinput ports. Simply assign the MIX Outputs to thedigital AES/EBU or SPDIF outputs, and send thatsignal in the digital domain to the Input of theDAT or CD-R recorder.

WHAT TYPE OF MIC PREAMPS DOESTHE DIGITAL 328 HAVE?

The Digital 328 incorporates Spirit's own UK-designed-and-built UltraMic Plus+ mic preampson channels 1-16. This acclaimed preamp designhas the ability to handle a wide range of signals,with a massive 66dB of gain range and +28dBumaximum input level. This caters for virtually allhigh level outputs that are likely to be passedthrough the preamp.

HOW DO GROUP ASSIGNMENTSWORK?

Simply select the channel you wish to assign, thenchoose the group(s) to which you wish to assign

SEC

TIO

N5:

Dig

ital

328 F

AQ

s

16

DIGITAL 328 FAQS

Guide.qxd 02/03/1999 11:25 Page 16

SEC

TIO

N5:

Dig

ital

328 F

AQ

s

17

them by pressing the button corresponding tothat group in the Select panel on the right side ofthe console. Alternatively, you can press and holdany one of the Group assign buttons and selectthe channel(s) you wish to assign to that GroupOut. You can also query which channels areassigned to specific Group Outs. Simply press andhold one of the Group assign buttons to seeinstantly which channel(s) are assigned to a spe-cific Group at any time.

WHERE DO THE GROUP OUTPUTSROUTE TO?

You can assign the Group Outputs the ADAT opti-cal outputs or the TDIF connectors, or to the addi-tional optical output (this is the how the Groupsare routed on power-up). The groups can also berouted to the Mix by holding down the Route toMix button and selecting the Group Select buttons

ARE ROUTING AND BUS ASSIGNMENTSSTORED IN SNAPSHOTS?

Yes; every digital function within a channel, suchas EQ, Pan and Group Output assignments can bestored internally using the Snapshot function.

WHAT ARE THE EQ FREQUENCYRANGES?

40Hz to 800Hz for the low frequency band, 200Hzto 8kHz for the mid band, and 1kHz to 20kHz forthe high frequency band.

HOW DOES THE SOLO/PFL SYSTEMWORK?

Each channel has its own Solo button - press onceto solo the channel, and again to clear it. In theSolo Control panel you can switch globallybetween PFL (Pre Fade Listen) and AFL (AfterFade Listen), and select SIP (Solo-In-Place). Thereis a Clear Solo function which will clear the solofrom all 16 channels. There is also also a trimadjust for the Solo system, which is the final faderon the masters bank.

HOW DO I SET THE AUXES TO BE PRE-/POST- FADER?

Hold down the Aux/FX Pre switch located on theright hand side of the console, and select which ofthe Aux and FX sends you want to be globallyPre/Post fader by using the Aux Select switcheslocated in the Rotary Controls section.

WHICH PARAMETERS CAN BE AUTO-MATED?

Snapshot Automation allows every function andparameter on the desk to be instantly recalled,except those associated with analogue controls eg.TRIM, HP Filters, C/Rm + phones output levelcontrols. Dynamic Automation allows for individ-ual control of each function and parameterthrough MIDI. All non-analogue functions of theconsole - including level, pan, EQ, and dynamics,aux level, and effectsparameters - have been assigned MIDI messageswhich allow software control through almost anyMIDI sequencing package.

HOW DO THE UNDO AND REDO FUNC-TIONS WORK?

Spirit Digital 328 offers non-destructive editing byusing the Undo/Redo function. This is useful forcomparing new EQ settings or FX settings.Whenever functions have been updated, you canpress the Undo button to return to the originalsettings. To return to the new settings, press Redo.There is only one level of Undo/Redo to avoid con-fusion. Snapshots can be used if multiple levels ofcomparisons are required.

Guide.qxd 02/03/1999 11:25 Page 17

SEC

TIO

N6:

Trouble

shooti

ng

18

I CAN'T HEAR ONE OR MORE INPUTCHANNELS AT THE MIX OUTPUT, EVENTHOUGH THE FADER IS UP AND THECHANNEL IS NOT MUTED...

Check that the channel is routed to the mix bus,either directly or via the groups. Hit the select but-ton(s) for the channel in question, and seewhether the Route To Mix button or any of theRoute To Group buttons are lit. If it's routed to agroup but you still can't hear it, check thegroup's level, and that it isn't muted. To do this,select the Master Fader bank, and check faderpositions and mute buttons for the eight faders onthe far left.

ONE OR MORE CHANNELS SOUNDVERY ODD - I KNOW THE INSTRUMENTSHOULDN'T SOUND LIKE THAT.

First check whether you've applied radical EQ tothe channel - press and hold the EQ In button inthe Select panel, and see whether the select but-tons on the channels in question are lit. If you'reusing two mono channels to record a stereoinstrument, check that both channels are inphase, and that the channels are panned left andright. (If you have copied settings from one chan-nel to the other, to give them the same EQ andFX/Aux settings, then you may have copied thepan settings as well. In the Chan Copy Setupmenu you can disable the copying of pan settingsbetween channels.)

I'M HEARING UNEXPECTED POPS ANDCLICKS, OR DISTORTION, ON DIGITALINPUTS.

This is almost certainly a wordclock problem. Ifyou are using an ADAT withyour 328, and using the optical interface, checkthat the ADAT is set to receive wordclock. Ensure

that wordclock is being properly distributed, andwhere appropriate that all devices are set to slaveto timecode from the appropriate inputs. Trymaking a different device the master - some DATrecorders, for example, must be the wordclockmaster when or changing the clock frequency ofthe wordclock master. Try turning everything off,and turning them on again in the order they areconnected in the wordclock chain, starting withthe master.

I CAN'T WORK OUT HOW TO ROUTECHANNELS IN STEREO THROUGHGROUPS TO THE MIX.

In order to use groups in stereo, you must firstlink adjacent pairs - 1&2, 3&4, 5&6, or 7&8. Ifgroups are not linked in this way, they are auto-matically routed in mono to the Mix. (Note thatthis applies to 328 software V1.1 and later). Tolink two groups, press and hold the Group Linkbutton in the bottom right hand corner of thefront panel, and press the select button for theodd-numbered Group. All channel pan settingsare now preserved when you route channelsthrough linked groups to the Mix. To route thegroups to the Mix, press and hold the Route ToMix button, and press either of the select buttonsfor the paired Groups.

MY SEQUENCER ISN'T RECORDING MYFADER MOVES AND OTHER CONTROLMOVES.

Check how the sequencer is set up - it is probablynot recording MIDI controller data, which is usedfor the 328's dynamic automation. Change yourrecording preferences to allow this to be recorded.Make sure MIDI Automation is switched on in the328 Automation Setup menu.

WHEN I USE DYNAMIC AUTOMATION,THE FADERS ARE JUMPING AROUNDINSTEAD OF MOVING SMOOTHLY.

This is caused by a MIDI loop via your sequencer.Turn off MIDI Thru so that data from the 328 isnot re-sent to its MIDI input.

TROUBLESHOOTING

Guide.qxd 02/03/1999 11:25 Page 18

For further information please contact us at thedetails overleaf, or alternatively visit our website:www.digital328.comYou will find information on the brochure, user guide,interface options, mixer maps, latest software andmuch more.

All contents © 1999 Spirit by Soundcraft. No part ofthis publication may be copied, transmitted or storedelectronically or otherwise for commercial gain,although the copyright holder will allow copying anddistribution for personal or non-profit use.

This guide has been written and compiled by PaulIreson, Shoot That Camel Inc., ex-editor Sound onSound magazine.

FURTHER INFORMATION

Spirit by Soundcraft TM,

Harman International

Industries Ltd.,

Cranborne House,

Cranborne Industrial Estate,

Cranborne Road, Potters Bar,

Herts EN6 3JN, England.

Tel: +44 (0)1707 665000

Fax: +44 (0)1707 665461

USA Distributors:

Spirit by Soundcraft TM Inc.,

4130 Citrus Avenue #9,

Rocklin, California 95677,

USA.

Tel: (916) 630 3960

Fax: (916) 630 3950

Part # ZL0502 E&OE.Spirit by Soundcraft reserves the right to alter specifications without prior notice.

www.spirit-by-soundcraft.co.uk

www.digital328.com

The Spirit Guideto Digital Mixing

Cover.qxd 2/3/99 11:58 am Page 1