RECORDING September 2022 - 58

INSIDE
THE BOX
with Joe Albano
ince the dawn of digital recording, recreating
the sound of analog has almost ironically been
a big part of modern mixing. This includes
emulating the unique character of analog tape.
S
Back to Analog
When digital audio emerged,
people celebrated the clean
sound. Gone was the distortion,
saturation, noise and hiss of analog
circuitry and media. But
we quickly realized that those
flaws-nonlinearities
in
the
recording
process-contributed a
desirable warmth, presence and
vibe to recorded music. Without
them, digital audio seemed too
clinical and lacked the character
that listeners had come to value.
DSP designers quickly turned to digital modeling to recreate
and reintroduce those aspects of analog equipment, including
the subtle saturation of analog tape.
Tape defined the sound of recorded music for decades, and
while it proved difficult to emulate at first, eventually, DSP designers
got the hang of it. Nowadays, many plugins provide
convincing simulations of the distinctive character of analog
tape and the very machines themselves.
The Mechanics of Tape
Analog tape is made up of magnetic particles suspended in
a slurry on the surface of the tape. On a blank tape, these particles-magnetic
domains-are arranged in random polarities,
but magnetic flux from the tape machine's record head realigns
them to follow the changing polarity of the voltage of an audio
waveform, tracing the shape of that waveform, resulting in a
magnetic recording of the audio wave across the length of the
tape. The physical nature of that process and its inherent limitations
produce the distinctive sound of analog tape.
58 RECORDING September 2022
Tape Saturation
At a certain point, higher-level (loud) signals will have realigned
all the magnetic particles, and any further increase in
signal level results in a flattening of the tops and bottoms of
the recorded wave. As with any audio signal, this clipping of
the wave generates harmonic distortion. With tape, this is
gradual. The signal is both slightly distorted and the level of
the loudest parts of the wave is reduced, causing compression.
This combination of gentle distortion and compression is
referred to as tape saturation, and it's the hallmark of analog
tape recording.
In just the right amount, tape saturation can make the recorded
signal sound bigger, fuller, and denser-analog engineers
deliberately ran hot signal levels to tape to create a small
amount of saturation, warming up the recordings in a highly
desirable way. All the plugins that emulate analog tape strive to
reproduce this, usually providing an input drive (gain) control
to adjust the strength of the effect, adding the character analog
engineers took for granted back in the day.
Bias
Low-level signals on tape also suffer from undesirable nonlinearities.
When quieter parts of the audio don't generate
enough magnetism at the recording head to overcome the inherent
inertia of the magnetic particles, the result is an inaccurate
waveshape and undesirable distortion.
An inaudible ultrasonic signal-called a Bias frequency-
was recorded along with the audio signal to guarantee enough
consistent sound to provide accurate recording at those low
levels. Many full-featured tape emulations offer the same user
bias adjustments found on professional tape machines.
TAPE
SEPTEMBER 2022 ISSUE
RECORDING September 2022

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