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VP-8IP / Sep 2013
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P R O C E S S M O D E S
FM Look Ahead Limiter
If desired, the FM output may be peak controlled by a special high-speed, feed forward
limiter with a 0.5 millisecond (500 microseconds) 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 within the control sidechain is better peak control
through finer definition of the audio waveform to be analyzed for limiting. Therefore,
oversampling of the audio signal itself is not only unnecessary, but wastes DSP resources.
The graphic below illustrates why control signal oversampling is 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 audio peaks could still be missed because their relative time alignment
would be identical!
FM Look Ahead Limiter Controls
The graphic on the right shows the
controls available for the look ahead
limiter. The following text describes
each control according to function.
Look Ahead Limiter Enable
When this check box is checked
the look ahead limiter is enabled. Note
that the look ahead limiter can be used
simultaneously with the main clipper
and precedes it. This feature allows for
a very powerful limiter/clipper behavior
tuning capability.
L/R Linked
When this box is checked the limiter’s left and right channel control signals are made
common. This prevents unnatural stereo image shifts when one channel needs to reduce
the signal in order to control peak excursions.
Lim/Clip (Limiter/Clipper) Drive
This controls the amount of drive to the following distortion-controlled clipper and/or
look ahead limiter, as chosen. The gain range of this control is +12dB/-18dB. The resolution
of this control is 0.01dB, fine enough for the most exacting drive level adjustments.
FM
