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Ariane
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range of control is usually less than 15 dB, but for the purpose of a modern AGC this range is too ‘limited.’ A
“Feedforward” (or “open loop”) detector analyses the signal before the variable gain element and creates a con-
trol signal that can accurately mirror level variations in the incoming audio. With a feedforward system the effec-
tive range is many decades of decibels, and its linearity of control is virtually perfect from one extreme of gain
to the other. For an initial AGC for audio of an unknown level, a feedforward system makes great sense. In the
Ariane, the control range is well over 40 dB, and the control characteristics are the same at both extremes.
Introducing The Ariane
The Ariane is a:
• High-quality digital,
• Two-channel,
• Multi-band,
• RMS-derived,
• Windowing release,
• Feedforward control…
automatic levelling processor for general purpose audio level management.
Each of these features of the Ariane were chosen to solve a particular problem that has manifested itself in
previously available levelling solutions. Processors with one or more of the above features have long been avail-
able, but the Ariane is the first leveller to bring this unique and significant combination of features together in a
unified design.
The above waveform chart demonstrates the peak level of a piece of typical music audio, in blue, superimposed
with its RMS energy value, the black line. Note that the RMS level does not closely follow the peak level but,
rather, represents the short-term average density of the audio. Now let’s superimpose the Ariane control system
upon that same RMS waveform.
The horizontal red, dashed line represents the Gate threshold. Whenever the RMS energy goes below that level
(numbers 1 through 7, above), the release is gated, and the Ariane’s gain holds steady, with no change. When
this is true, the broad horizontal band is red (the vertical dimension of the multi colour band represents the
Ariane’s “window”).
When the audio’s RMS energy drops below the window, but still remains above the Gate threshold, the window
releases (numbers 8 through 13), and the window band is green, indicating an increase in gain.
Whenever the RMS energy stays inside within the range of the window, the band is Yellow, and the audio level
is unchanged, just as it was when it was gated.
In both charts, time goes from left to right, and higher amplitude is upward; in the lower chart, the broad multicol-
our band’s position vertically indicates more gain the lower it goes.
It’s easy to see that the Ariane can be adjusted to spend most of its time holding steady, with no level change.
This is the little bit of ‘magic’ that makes the Ariane sounds so good!