Section 28: Inputs Tab
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Page 252
T E C H N O L O G Y
28.4.
Phantom Power
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codecs also have the ability to supply 15 volts of phantom power to the
microphone inputs. Simply check the
Enable Mic phantom power
box to switch
this function on.
WARNING:
Please check the powering specifications of the microphones you
are using with your codec to ensure they will operate effectively and
to avoid
damaging them.
28.5.
Intelligent Gain Control
All codecs also have the
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Intelligent Gain
Control (
IGC
)
system, which makes controlling
levels a simple non-technical exercise.
IGC
was
developed to enable announcers to forget about
panel controls and to focus on program content.
28.5.1.
How it works:
The microphone input level is controlled by the input level digipot on the
codec. All analogue audio inputs are digitized by a high quality stereo 24-bit
analogue-to-digital (A to D) converter. This serial data stream is then fed to an
extremely fast 32-bit Digital Signal Processor (DSP) that encodes the audio
data.
The DSP measures the amplitude of incoming signals and if the levels exceed
acceptable limits, the DSP will automatically control the digipot to decrease
the level of the incoming signal back to an acceptable level. This
IGC
is
enabled almost instantaneously.
28.5.2.
IGC Enable Mode
IGC
has two operational modes. In
IGC
Enable
mode, audio levels will be
automatically adjusted downwards until they are acceptable. The input level
will remain at this point until the input digipot is adjusted again by the user. In
addition, the channel on light will flash until the input pot is adjusted. The
flashing button notifies the codec operator that
IGC
has been initiated.
28.5.3.
IGC Auto Level
In
IGC Auto Lvl
mode (the default setting for manual default profiles), audio
levels are automatically adjusted downwards until they are acceptable.
However, once the codec detects that the incoming audio levels have reduced
sufficiently, the input level will be returned to the previous setting before
IGC
Auto Lvl
control was enabled. The codec takes just 250 milliseconds to detect
audio levels have returned to normal (after
IGC Auto Lvl
has been initiated)
and will then return the digipot levels to the previous setting in half a second.
This response is linear. The channel on light will flash while
IGC Auto Lvl
is
activated.
