Vol ume, Par t 1: Fiddling with Fad e r s By Alex Case t is an axiom of the roc k and roll rec o r ding craft that of balance. Re l ying almost entirel y on volume control s , louder is better. The good old volume control is a pow- balancing a mix is one of the most important skills an Ierful audio effect—and ever y studio has at least one. engineer must master. This and the next episode of Nuts & Boltswill exp l o r e the many applications of this humble effect—some obvi - On the level ou s , and some not so obvi o u s . If music is picked up with a mi c ro p h o n e , you’ll need a A sense of balance mi c r ophone prea m p l i f i e r . Consider the first step in Guess what? Mic preamps are building a mix. Ca re f u l l y, sy s - In pop music, if the guitar is nothing more than vol u m e te m a t i c a l l y, and iterat i vel y you dev i c e s . And we’ v e got to set adjust and readjust the vol - louder than the vocals, you ’ r e the volume just right when we ume and pan position of each going to have trouble selling rec o r d to tape or hard disk tra c k until the combination (see sideba r ) . starts to make musical sense. records. You work to find a Because all equipment has At that point the mix is bal- some noise, we natural l y try to anced—the song can stand on balance that’s fun to listen to, rec o r d music at as high a level its own , and ever y trac k con- as possible so that the mus i c a l tributes to the music without yet supports the music and wavef orms drown out the ob l i t e r ating other parts. reveals the song’s subtleties. noise floor. So it seems true In pop mu s i c , u s u a l ly the that louder is indeed better. vocal and the snare sit pre t t y The question is, ho w loud? loud in the mix, dead center, The r e are two differen t with the other pieces of the st r ategies for setting rec o r d- a r rangement (tra cks and ing level s , depending on effects) filling in around and underneath. If the guitar whether the storage format is digital or analog. is louder than the vo c a l s , yo u ’ re pro b ab ly going to have You ’ v e undoubtedly heard that for digital rec o rd i n g , t rouble selling re c o rd s . If you can’t hear the piano the goal is to “print the signal as hot as possible without when the sax play s , the song loses musical impact. S o going over .” Le t ’ s think a little bit about what that means. you wo rk hard to find a balance that’s fun to listen to, Pre s s u r e in the air becomes voltage on a wire (thanks supports the mu s i c , and reveals all the complexity and to the microp h o n e ) , wh i c h then becomes num b e r s on subtlety of the song. tape or disk (thanks to the analog-to-digital conver t e r ) . This first step of a mix session is rea l l y a part of ev e r y As the music gets louder in the air, the corres p o n d i n g se s s i o n . For trac king and overd u bb i n g , the player s can’t voltage gets higher on the mic cabl e . But at some point pl a y, the engineer can’t hear, and the producer can’t pro- the num b e r s getting stored by the digital system can’t duce until the signals from all the live microp h o n e s , get any bigger—it maxes out in muc h the same way that rec o r ded track s , and effects are brought into some kind a child counting on his or her fingers runs out at ten. RECORDING JUNE 2001 Second, listen carefully. This type of distortion is extremely harsh; it’s not a particularly musical effect, so it’s best used sparingly if at all. But of course it’s not strictly forbidden—music tends to rebel. On analog magnetic re c o rding sys- t e m s , you typically re c o rd as hot as p o s s i b l e , and occasionally go ove r. U n l i ke digital audio, a n a l og audio d o e s n ’t typically hit such a hard and fast limit; instead, it distorts gra d u a l- ly as you begin to exceed its comfo r t ra n g e . This gradual distortion at the peaks is called soft clipping, s h ow n in Fi g u re 2. At lower amplitudes, the analog magnetic storage medium tra cks ve ry a c c u ra t e ly with the wave fo r m . As the audio signal starts to get too loud, the analog storage format can’t ke e p u p. It starts to re c o rd a signal that’s not quite as loud. As it runs out of s t e a m , it does so gra c e f u l ly. L o o k c a re f u l ly and you might notice that ove rd r iven analog tape looks a lot l i ke compre s s i o n . A quick glance at my effects ra ck reminds me: compression is an effect. I ’ ve bought ra ck spaces and pull d own menus full of compre s s i o n . C a n you ove rd r ive analog magnetic re c o rd e rs for an effect? You betch a . So we find ours e l ves using volume as an effect simply by setting levels as we re c o rd mu s i c . An a l o g machi n e s , with faint tape hi s s , pr efer audio wavef orms without quiet passages (low vol u m e ) . Whi l e digital systems don’t have tape hiss, th e y do introduce other sonic artifac t s at low level s , as we’ll discuss in a fu t u r e Nuts and Bolts article. St i l l , this low noise floor was a dri- ving for ce in the transition from ana- lo g to digital audio. Classical and jazz en g i n e e r s have to rec o r d acoustic At that point the digital data no longer fol l o ws the music with a wide dynamic ran g e — m usic that sometimes musical wavef orm (see Fig u r e 1). This is a kind of distor- has long, op e n , quiet spaces. For this genre of rec o rd i n g , tion known as hard clipping. The peaks are clipped off, the nearly silent noise floor of digital storage was a gone for ever . dr eam come true. Obv i o u s l y, the way to prevent this kind of distortion is to Ro c k and rol l , on the other hand, tends to have a muc h ma k e sure the analog levels going into the digital rec o rd e r mo r e narrow dynamic ran g e . The song kicks in and rare l y ne ver for ce the system past its maximum . The meters will lets up; hiss can’t raise its ugly head over the screa m i n g help you here. Digital systems general l y have meters that vocals and grinding guitars. me a s u r e the amplitude of the signal in decibels below full Mo re o ver , as we know from listening to rad i o , li s t e n i n g s c a l e ,w h i ch is the “ten fingers” point at which the digital to great mixes, and experimenting in our own studios, system has rea c hed its maximum digital val u e . roc k and roll also loves a bit of compres s i o n . As a res u l t , If you are intrigued by the wavef orm shown in the even in this ver y digital age, ma n y pop rec o r ds are still lo wer part of Fig u r e 1 and are wondering what it sounds rec o r ded onto analog tape. li ke , you might want to overd r i ve the digital system on Ad ding further iron y, these days digital audio devi c e s pu rp o s e . Be my guest, but be caref u l . Firs t , monitor at a ar e consistently less exp e n s i ve to own and operate than lo w level .