Recording - March 2015 - 48

Admittedly, this occurs at a really high
level, but it's even possible with something like a Shure SM57 close to a snare
drum. The solution here is to first recognize what's happening, and then put a
10 or 20 dB pad in line between the mic
and the input connector on the interface.
That way you won't clip the front end and
the input gain control can do its job.
And while we're talking about setting
input levels, you should try to keep the
eyeball average down around -20 dBFS
(again, reading the Pro Tools meters). This
should allow sufficient headroom for
nearly all voices and instruments, but do
a dry run first to make sure... and it's

does its arithmetic, you may indeed hear some loss of quality in the mix. Better to follow the rules than to push the arithmetic to the limit.
Clipping is only as bad as it sounds to you. If you can hear it, then you'd better figure out why and fix the problem. If it's just an occasional sample that hits full scale,
that's probably not going to be noticed by anyone not watching the red lights.
But there's some other evil lurking when you get a mix close to full scale, because a
digital-to-analog converter can produce a peak level analog between two adjacent
samples that are a little lower in level. It's possible that all of your samples are below
the clipping level but that what comes out of the converter may have a peak that's
clipped by the analog output stage. Generally these things are designed, on both the
front and back end of the chain, to have the analog stage crap out very close to fullscale digital, but it's something that gets cheated on occasionally.
For example, in this interface I was telling you about that could clip the analog input
and still not have digital clipping, when playing back a mix that peaked at 0 dBFS,
the headphone output would clip with the headphone volume control well below maximum with any headphone impedance that I tried. Mind you, it was pretty darn loud
before it hit clipping, but if you wanted it louder, you'd be listening to a clipped mix.
One final note: if you were to look at a lot of mixes of contemporary rock music,
you'd see a lot of clipping. They tolerate it in the name of loudness. Fortunately, that
trend is starting to go away. Don't contribute to it. If your mix isn't loud enough, turn
up your playback volume!-MR

"You ask if the direction is to avoid clipping at all costs, and I say YES!
It's easy to avoid (once you know how), so why not?"-Giles Reaves

always a good idea to record the dry run
anyway just in case it's the best take!
Your attempts to build up a strong vocal
track or drum submix aren't working out
because you're working backwards. You
should start with the output fader at unity
gain, which may be all the way up or
somewhere around 2/3 to 3/4 fully up-
there's probably a mark on the scale for it.
Then drop the level of the tracks going into
that auxiliary mix so that the level of the
mix stays down in the -20 dBFS range.
You can be a little less conservative here
since you can watch the meters; if you do
start creeping up too high, you can just run
through the mix again without doing any
harm other than wasting a few minutes.
Also, if there's a single track that at one
point makes the mix go into clipping, consider making a gain adjustment to the
blood curdling scream on that one track
to keep things in check.
Today, with 32-bit floating point and
24-bit fixed point arithmetic pretty common, you can "overload" a mix bus and
bring it down to under 0 dBFS peak with
its fader, but depending on how the DAW
48

RECORDING March 2015

Paul Vnuk Jr.
Hey Steve! You are describing very common gain staging issues. First off, it sounds
like you're trying to make your mixes compete with fully mastered CDs, and I can say
right away that you should never compare them side by side for loudness and presence. A favorite released track can serve as a reference point for EQ, compression,
panning, effects and such... but never for loudness.
Why? Because almost all professionally released tracks will have gone through the mastering process. In said process the mastering engineer will apply final EQ, compression,
and limiting to the finished mix, so that it competes favorably with other professionallyreleased products with respect to both level and overall sound. Your mixes can't compete
with that.
Taking a step back, let's look at levels and clipping while mixing. In the digital world, if
it clips, it's bad, period. You need to adjust your thinking from "How loud can I get each
track before it clips?" to "How much headroom can I give each track?" By headroom, I
mean the difference between your loudest peak and the unbreakable ceiling of 0 dBFS.
The best practice to get into is to look at your meters. Aim to have the average volume of your tracks hover around -12 dB, your quiet sections around -18 dB, and your
absolute loudest sections peak no higher than -6 dB. This then gives you an additional 6 dB of headroom just in case something gets out of hand in the mix.
Your final mix will not sound as loud as a finished CD-and it shouldn't; that's for
mastering. If you do need to compare the quality of your mix to a professional one,
turn the professional mix down until it is level-matched to your overall mix volume.
By adopting this workflow you should avoid clipping your mix, your plug-ins, any
inter-sample peaks you may get after D/A conversion, and more. In the end, you will
have a nicely dynamic, balanced and good-sounding mix... one that will sound even
better when mastered.-PV

Recording - March 2015

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