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VP-8IP / Sep 2013
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P R O C E S S M O D E S
AM Look Ahead Limiter
If desired, the AM output may be peak controlled by a highly oversampled feed forward
limiter with a 0.5 millisecond look ahead time. The control path (not the audio path) is
highly oversampled in order to achieve extremely precise peak control. The primary goal
of oversampling the control sidechain is better peak control through finer definition of the
audio waveform. Therefore, oversampling of the audio signal itself is not only unnecessary,
but wastes DSP resources. The graphic below illustrates why control signal oversampling
is more effective.
By sampling the audio waveform with finer resolution we can detect peak excursions that
would be missed otherwise. In fact, if both the audio and control signals were oversampled
peaks would still be missed because their relative time alignment would be identical!
AM Look Ahead Limiter Controls
The graphic below shows the controls
available for the look ahead limiter. The
following text describes each control
according to function.
Look Ahead Limiter Enable
When the
Look Ahead Limiter Enable
is checked the look ahead limiter is
enabled. Likewise, when
this check box is
not checked, final peak limiting is via the
distortion cancelled clipper only.
The look ahead limiter and distor-
tion cancelled clipper
may
be used simultaneously if desired, though precisely how to
adjust everything when both are operating simultaneously becomes “artistically-driven.”
Adjustment can get tedious and how to do it is even harder to explain in writing. Therefore
we feel it is not only beyond the scope of this manual, but also falls into the realm of “if
you really want to do this please call us for advice.”
L/R Linked
When this box is checked the look ahead limiter’s left and right channel control signals
are common. This prevents unnatural stereo image shifts when one channel needs to reduce
the signal in order to control peak excursions.
AM
