Chapter 8: Getting In Deeper: Recording; Watch Your Levels While Recording - Alesis iO14 Reference Manual

Getting In Deeper: Recording
8

Watch Your Levels While Recording

A basic principle in digital recording is that you want to capture the
loudest signal you can, but at the same time you never, ever want
to exceed the maximum digital threshold. If you do, you'll
introduce the nasty distortion known as "digital clipping" into your
recording.
Your Alesis io provides a number of methods to help you avoid
digital clipping:
1. 24-bit recording - Operating at 24 bits, the io offers 256
times more resolution than that of 16-bit compact disks.
One result of that increased resolution is that you have far
more headroom to work within. You can easily record such
that your loudest peaks for an unpredictable player are no
greater than -12dBfs to -18dBfs. ("dBfs" stands for "decibels
at full scale". In digital, once you reach full scale, you're using
all of the available resolution. Attempting to record at
greater than 0dBfs results in digital clipping.)
2. Dedicated hardware metering of digital signal - The
meters on the front panel of the io show your audio signal as
it is seen by the digital converters. In other words, they're
totally accurate, unlike analog meters which only approximate
the digital signal strength.
3. Dedicated input monitoring panel - In the HDM
application, there is a special tab for Input Monitoring. This
tab provides an uncluttered view of the strength of your
incoming signals. (Note that the tab is always in "narrow"
view to provide a quick overview of all the channels.)
4. Pre-fader level monitoring - Again in the HDM application,
all metering is always "pre-fader." That means that the
metering shown to you is independent of how you set the
volume sliders. This allows you to see your actual signal
strength even as you're creating various custom mixes for the
people you are recording.
If you haven't experienced
digital clipping before, spend
a moment to learn what it
sounds like. Plug a
microphone or line level
source into your io. In the
HDM panel, turn up the fader
for that channel in an
appropriate output tab. Be
sure that the "Direct Mon"
slider towards the right is
turned up as well. You want
to hear your audio.
Watch the HDM panel
metering, and turn up the io's
preamp until you're
registering signals near the
top of the scale. Then, go just
a bit further. Notice the
harsh, buzzing kind of
distortion that appears. This
distortion is digital clipping.
It can ruin your recordings
and should be avoided at all
costs (unless you want it as a
special, unmusical effect).
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