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AM-10HD / Aug 2008
A M - 1 0 H D G U I
Gate Threshold
The AGC Gate Threshold control sets the audio level below which the audio
gain reduction values are held until audio returns. This control can be set to OFF or
adjusted over the range of ‑79.0dB to ‑20.0dB.
In each of the five bands there is also a Gate Threshold Trim control allowing
offsets of +/‑6dB to be made to each band referenced to the main Gate Threshold
setting. This allows precise Gate thresholds on a band by band basis as appropriate
for the program format requirements.
Example: Suppose the AGC Gate Threshold control is set to ‑40.0dB and the
controls for the individual bands are set as in the example below:
In this example, Band 1’s Gate Threshold has been offset by +3db, which means
its actual gate threshold is now ‑37dB, or 3dB less sensitive than band 3 (which is
still set at the “0” reference line). This will cause band 1 to need a higher audio level
before it will “un‑gate” and allow the gain to increase. Setting the gate this way pre
‑
vents unnatural increases in low frequency gain that might be undesirable. The Gate
Thresholds may be offset this way in any of the bands as the application warrants.
Band Coupling
The Coupling control has one specific purpose – to keep the gains of bands 1, 2,
4, and 5 from exceeding the gain of band 3 when those “outer” bands are “un‑gated.”
This prevents unnatural gain rush‑up by the bands at the extremes of the audio spec‑
trum when such behavior would be undesirable.
Without the “Coupling” feature the bands at the frequency extremes could increase
their gains when they shouldn’t and cause a spectrally incorrect sonic mixture at the
output of the five band section.
Band 3 was chose as the “master” band for the Coupling control simply because
that band is in the approximate center of the audio spectrum.
Five Band AGC Gate Offset Controls
