volume part 1

8/13/2019 Volume Part 1

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RECO RDIN G JUN E 2001

Vol ume, Par t 1 : Fiddl ing wit h Fader sB y A l ex Case

It is an a xiom of the rock and roll recording cra f t tha tlouder is bett er.The good old volume control is a pow-erful audio effectand every studio has at least one.

This and t he next e pisode of Nuts & Bol tswill explorethe ma ny applicat ions of t his humble effectsome obvi-ous, and some not so obvious.

A sense of balanceConsider the f irst step in

bui ld ing a mix . Ca refully, sys-t ema t ica ll y, an d i te r at ively youadjus t and readjust t he vol-ume and pa n position of eacht ra ck until the combinationstart s to ma ke musical sense.At tha t po in t the mix is ba l-ancedthe song can stand onits own, a n d ev ery track con-tribut es to the music withoutob lit era t ing o ther par ts .

In pop mu s i c , u sua l ly the

vocal and t he snare s i t pret t ylo ud in th e m ix , dead c en te r,wi th the o ther p ieces o f thea r r an gem en t (t r a ck s an d

e f fec t s ) f i l lin g in a rou n d an d u n dern ea t h . I f th e gu i t a ris louder tha n the vo c a ls , y ou re prob a b ly go ing to havet rouble se l l ing record s. I f y ou c an t h ea r th e p ian owh en th e s ax p lay s , th e son g lo ses m u s ic a l im p ac t . S oyou wo rk hard to f ind a ba lance th a t s fun to l is ten to ,supports the mu s ic , an d revea l s a l l t h e c o m p lexi ty an dsubtle ty o f t he song .

This first st ep of a mix session is rea lly a par t o f ever ysession. Fo r t ra cking and overdubb ing, th e players cantplay, the engineer can t hear , and the producer can t pro-

duce until the signals from all t he live microphones,re corded track s, and e f f ec ts are brought in to some kind

o f ba l an c e. R elying almost entire ly on volume controls,ba lancing a mix is one of the most importan t skills anengineer must ma ster.

On the level

If music is picked up w ith amicrophone, you l l need amicrophone prea mplif ier.Guess wha t? Mic preamps a renothing more than volumedevices. And weve got to setthe volume just right w hen were cord to tape or hard d isk(see sideb a r).

Because a l l equipment ha ssome noise , we na tura lly try tore cord music at as high a levelas possible so that the musica lwaveforms drown out thenoise f loor. So it seems truetha t louder is indeed bet ter.

The question is , how loud?There are two dif ferent

st rat egies for setting record -ing levels, depen d ing o n

whether the storage format is digital or analog.Youve undoubtedly heard t hat for digital recording,

the goal is to print the signal as hot a s possible withoutgoing over. Let s think a l i tt le bit about wha t that m eans.

P ressure in the air becomes volta ge on a wire ( thanksto the microphone), w hich then becomes numbers onta pe or d isk (thanks to the ana log-to-digital convert er).As the music gets louder in the a ir, the correspond ingvoltage get s higher on the mic cab le. But a t some poin tthe numbers getting stored by the digit al system cant

get a ny biggerit ma xes out in much the same way t ha ta child counting on his or her f ingers runs out a t t en.

In pop music, i f t he guit ar is

l ouder t han t he vocal s , your e

go ing t o have t r oubl e sel l ing

r ecor ds. You wor k t o f ind a

bal an ce t h at s f u n t o l is t en t o ,

yet suppor t s t he music and

r eveal s t he song s sub t l et ies .


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At tha t po in t the d ig i ta l da ta no longer follows the

musical wa veform (see Figure 1). This is a kind of distor-tion known a s hard clipping. The pea ks are clipped off ,gone forever.

Ob viously, the way t o prevent this kind of distortion is to

ma ke sure the a nalog levels going into the digita l recordernever force the system past its maximum. The met ers willhelp you here. Digital systems generally have meters thatmea sure the amplitud e of the signal in decibels below fulls c a le ,w h i ch is t he ten f ingers poin t a t which the d ig i ta lsystem has rea ched its maximum digital value.

I f you are intrigued by t he waveform shown in thelower part of Figure 1 and a re wondering wha t i t soundslike, you might want to overdrive the digita l system onpurpose. B e m y gu est , bu t be c a re ful. First , m o ni tor a t a

low level. This kind of d istortion is full of high fre q uencyenergy tha t can melt tweeters.

Second, listen care fully . This type ofdistortion is extremely ha rsh; i t s not apar t icu lar ly musica l e f fec t , so it s bes tused spar ingly i f a t a l l . But o f courseit s not strictly forbid denmusic

tends to rebel .On ana log magn etic re c o rd ing sys-

t e m s , y o u ty p ic a l ly re c o rd a s h o t a sp o s si b l e , and occas ional ly go ove r.U n l i k e d ig i t a l au d io , a na l og au d iod o e s n t typ ica l ly h i t such a hard andf a s t l im it ; in stead , i t d i s to r t s g r a d ua l-ly as you begin to exceed i ts comfo r tra ng e . Th is g r adu a l d i s to r t ion a t th epeaks is ca l led so f t c l ipping , s h ow nin Fi g u re 2.

At lo wer am p l itu des , th e an a logmagne tic s torage medium tra cks ve rya cc u ra t e ly wi t h the wave form. As t h e

audio s ignal s tar t s to ge t too loud,the ana log s torage format can t ke e pup . I t s t a r t s to re c o rd a s ign a l th a t sn o t q u i te a s lo ud . As i t ru n s ou t o fs t e a m , i t do es so g ra c e f u l l y. L oo kc a re f u ll y an d y o u m igh t n o t i c e th a toverdr iven analog ta pe looks a lo tl i ke compre s s i on .

A quick g lan ce a t my e f f ec ts ra ckreminds me: compress ion is an e f fec t .I ve b ought ra ck spaces a nd pul ld own me nus full of compres s io n . C a nyou ove rd rive ana log magneticre co rd e rs for a n e f fec t? You betch a .So w e f ind ours e lves using volume asan e f fec t s imply by se t t ing levels aswe rec o rd mus i c .

Ana log machines, w i t h f a in t t a p ehiss, prefer audio wave forms withoutquiet passages ( low volume). Whiledigital systems dont have t ape hiss,t hey do introduce other sonic artifa ct sat low levels, as well discuss in afut ure Nuts and B olts artic le.

S t ill, th is low noise f loor was a d r i-ving force in the t ransition from ana-log to d ig ita l a udio. Class ica l and jazzengineers have to record a coustic

music with a wide dyna mic ra ngemusic tha t sometimes

h as lon g , open, quie t spaces. For th is genre of record ing,the nea rly silent noise f loor of digital storage wa s ad ream come true.

R ock and roll, o n th e o th er h an d , ten ds to h ave a m uch

more narrow dynamic range. The song kicks in and ra relylets up; hiss cant raise its ugly hea d over the screa mingvocals and grinding guitars .

Moreover, as we know from listening to ra d io, listeningto great mixes, and experimenting in our own studios,ro ck and roll also loves a bit of compression. As a result ,even in this very d igi t a l age , ma ny pop records are sti l lre corded onto ana log ta pe .

Adding further irony, these days digita l audio devicesa re consistently less expensive to own and operate tha n

professional ana log audio ta pe machines. Today, we essen-t ia lly must pay ext ra for t he ta pe compression effect.


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G iven a choice , th e sou n d q u a l ityd if f erences between analog and digi-ta l recorders as they react t o wherethe volume knob is set are a key fa c-tor in selecting which format t o useon a recording project . And heresanothe r clear case of using the vol-ume knob as an effect.

Flavor

In the recording studio, we gener-a lly run into two ty pes of ana log vol-ume control: the var iable resistorand the voltage controlled amplif ier.

Electrical resistance is a propertyof all mat erials describing how mucht hey restrict the flow of electricity.Materia ls with very high resist a ncea re classif ied a s i nsulat or s; they pret -ty much d ont conduct electricity a ta ll. We appreciate t his property whenwe handle things like power cords.

At the other ext reme, devices wit hve ry low resista nce fall into the cate-

gory of conductor s. Copper wire is aconvenient exa mple. The copper

within that power cable conductselectricity from the wall outlet to thepiece o f audio equipment , ge t t ingthe LE Ds to f l icker, mot ivating themet ers to twitch , enab ling us toma ke and record music.

The volume knob on a homestereo , e lec tr ic gu i tar, or ana log syn-thesizer is (wit h a f ew m odel-specificexceptions) a var iable resist or. Se t toa high resist a nce, e lec t ri ci ty h ast rouble f lowing and the volume isa t tenua ted . To turn up t he volume,lower the resista nce and let the

audio waveform through. Also ca l ledpotent iomet ers, we typ ica l ly th ink o fthem as simple volume controls.

In the recording studio, we have tolook more closely a t our volume con-t rols because there is a second ty pe:volta ge controlled a mplif iers. H epcats resort to three letter acronymsVC A. The idea behind them is simpleand clever.

I f the fa der on an a nalog console isa potent iometer, i t ma kes sense to

Because al l equ ipment has no ise, we t r y t o

r eco r d mu s ic at a h ig h l evel so t h at t h e

mus ic d r owns ou t t he no ise f l oo r . So it

seems t r ue t hat l ouder is i ndeed bet t er ....

Excerpted fromthe June edition of RECORDINGmagazine.2001 Music Maker Publications, Inc. Reprinted withpermission.

5412 Idylwild Trail, Suite 100, Boulder, CO80301

Tel: (303) 516-9118 Fax: (303) 516-9119For SubscriptionInformation, call: 1-800-582-8326


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picture the fader as a va r iable resis-tor. But in the case o f a VC A, thefad er tha t sits on the console is sepa-rated from the audio by one layer.Instead o f having tha t s l ider on the

console physica lly adjust the re sis-tance in a potent iometer, i t adjus ts acont rol volt a ge. This control volt a gein turn adjus ts the a mount o f ga inon an a mplif ier.

Most compressors use VCAs, w hicha re capable of rea cting to volt a gechanges very q uickly. And for con-soles, the only o ther way to havesomething other than t he engineerad just the level would be to stick amotor on the fa der. This is a pricey,complicated option, but motorizedfa ders are certainly availa b lea ndat a n ever-decreasing price.

Automation

Mix automation can do manythings these days. I f you have a h ipdigital audio workstation or digitalconsole, y ou c an au to ma te i t so th a ti t wakes you to music first thing inthe morning (noon), start s the coffee

ma ke r, an d d raws a warm ba th .While this is all quite useful,

automa tion is almost always justused for two very simple processes:

fader r ides and mut es. The point ofpushing fa ders and pressing mutebutt ons? Controlling volume.

Not too long ago even the fa nciestconsoles o f fered the a bi l i ty to a u to-mate only the fad ers and the cu t(mute) buttons . S tudios spent a fe whundred thousand dol lars on a topof the line, stat e-of-the-art consoleand s t i ll couldn t au tomat e pan pots ,

aux sends , equal izers, compressors ,or reverbs.

. ..The quest ion is,

h o w l o u d?


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But a s we know f rom all the music released from thebeginning of time up to about 1995, extra ordina rily elabo-

rate a nd complicated mixes were built with t his rela t ivelylimited a mount of automation capabilit y. Clever volumeef fect smostly using VCA-ba sed a utoma tionare the key.

For exa mple, us ing the humble mute switch , t h e m ixengineer controls the mult it ra ck arrangement . C ut t h eba ss in the ext ra bar before the chorus, pul l the f lu te outof the horn part until the last chorus, et c. This sort of mixmove happens throughout pop music. B ut c heck out a nex t reme exam ple by listening t o U2s A cht ung Baby. Thealbum begins with some heavy cut act ivity a s the drumsand b ass en ter a t t he top o f the f i rst tune o f the a lbum, Zoo St a t ion .

Automat ing fader rid es in support of the arra ngementis a na tura l appl ica t ion of a u tomation. Maybe i t ma kes

sense to push the guita r up in the choruses, p ul l th eCha mberlin down during the guita r solo, and such.Idea lly, the band (maybe w ith the advice of a producer)

gets these dyna mics right in their performance. But in thestudio, the full arrangement of the song may not cometogether for several months as overdubs are gradua llya dded to the tune. Fader rides may be just the ticket tohelp this assembly of tra cks fa ll into a single piece of music.

Volume changes are a utomated just to keep the song inbal ance as mult it ra ck components of the song come a ndgo. But i t s usually a g ood idea t o keep these moves quitesubtle; theyre aimed a t t he musical interpretation of themix, t rying to ma ke the song feel right. With few e xcep-t ions, it should prett y much never sound like a fader wa smoved . Listeners want to hear the music, not the console.

Another a utomat ed volume effect is the Aut oma t edSend . So me very sophisticated m ix elements can be cre-at ed this way sends. Automat ion is employed to add rich

and spacious reverb to the vocal in the bridge only, int ro -duce rhy thmic delay to the ba ckground voca ls on keywords, increase the chorus effect on t he orchest ra lstrings in the verses, a dd distortion to the guita r in the

final chorus, et c.The a utomate d sendjust another volume effe ctoffers

a w ay to layer in areas of more or less effects, using noth-ing more tha n straight forw ard faders and cuts automation.

Well keep digging deeper into volume next month,moving beyond fa ders and exploring the f iner points ofcompression, e xpa nsion, ga t ing, a n d t remolo , an d h ow volume af fects the eq curve. St ay tuned.

Gettin g paid t o play the volume control i s why A lex Case

became a recordi ng engineer. He used t o do it f or free.Speakup t o case@record i ngmag.com .

Dynamic Range

Musical dynamics are so important to composition and performance that they are notat-edon every score and governed closely by every band leader, orchestra conductor, and

musicdirector. Making clever use of loud partsand soft partsis a fundamental part of com-position andarranging.In the studio we must concern ourselves with a different sort of dynamics: Audio

Dynamics. Followalong in Figure 3 as we keepcareful control over the rangeof ampli-tudes that we encounter when recording audio signals.

Exploring the upper limit of dynamicrange comes naturally to most of us. We turn itupwhatever it isuntil it hurtsour ears, our equipment, or the music. Cranking it tillit distorts. It seems to be the sole determinant for the position of the volume knob on mostguitar amps (including mine), car radios (at least for the car in thelane next to me),portablestereos(thejogger who just passed me), home stereos(my neighbor in my fresh-man year collegedorm) Herewe have encountereda basicproperty of all audio equip-ment: turn it uptoo loud, and distortion results.

At theother extreme (turning it down too much) lives a different audio challenge: westart to hear the inherent noise of the audio equipment we are using. All audio equipmenthas a noise floorequalizers, compressors, microphones, andeven patch cables. Yup.Even a cable madeof pure goldmanufactured in zero gravity during the winter solstice ofa non-leap year will still have a noise floor, however faint.

A constant part of the recordingcraft is using our equipment in the safe zone betweenthese two extremes. This is thedynamic range, anditsquantified in decibels (dB). The tar-get nominal level is typically labeled0 VU (thats a zero, not an O). At 0 VU the musicgetsthrough well above the self-noise of the equipment, but safely under the point where itstarts to distort.

If we recordedpure sinewavesfor a living, wedturn the signal upright to the pointof distortion, back off a smidge in level, and hit Record. However, the amplitudeof a reallife musical waveformraces wildly up anddown dueto both the character of theparticu-lar musical instrument and the way it isbeingplayed.

Electricguitars ampscranked to the limitat that much savored edge of becoming firehazardshavevery little dynamicrange. If you havent already witnessedthis yourself,record a guitar theway Spinal Taps Nigel Tufnel doeswith the amp set to eleven. Youll

observe the meters on your console and multitrack zipupat the downbeat. Andthey bare-ly move until the end of the song.

Percussion, on the other hand, can bea complicatedpattern of hardhitsand delicate taps.Such an instrument isa challengeto recordwell. The musical dynamicrange of theinstrumentmust somehowbe made to fit within theaudio dynamicrange of your studiosequipment.

Accommodating the unpredictability of all musical events, we record at a level wellbelowthe point where distortion begins. Theamplitude distance (expressedin decibels)between thetarget operating level0 VUandtheonset of distortion iscalledhead-ro om . This gives us a safety cushion to absorb the musical dynamics without exceedingtheaudio dynamicrange of the gear.

The relative level of thenoise floor comparedto 0 VU, again expressedin decibels, isthesignal-to-noise r atio. The trick, of course, isto sendyour audio signal through at a levelwell above the noise floor so that listeners wont even hear that hiss, hum, grit andgunkthat might be lurkingdown in the depths of each piece of equipment.

Makingeffective use of dynamicrange influences not just howwerecord to tape, buthowwe use a compressor, a de-esser, a reverb, or any other pieceof gear.

Look car ef u l l y and you might

n o t ice t h at o ver d r iven an al o g

t ape l ooks l ike compr ess ion .

volume part 1

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