Automatic Gain Control (AGC) Component
The purpose of the Automatic Gain Control is to control the overall dynamic range of the Output when the Input level changes.
The AGC can be adjusted from unity (1:1) with the Input, to an almost flat (100:1 - very little amplitude variation) Output. The AGC automatically adjusts the Gain to compensate for high or low Inputs. The control settings for the AGC Component affect all the Input Channels based on calculations made using the highest Input level. If you want to separately control the AGC for multiple Channels, simply add more AGC Components.
Inputs and Outputs
Note: The number of signal pins is variable and set in the component's Type Property.
Input Pins
Input
Audio signal pins are represented by a (
) circle, and traditional wiring is represented by a thin black line.
By default, the Automatic Gain Control component is set to a Mono channel, which provides one input. Additionally, you can set the Properties to allow for Stereo, which gives you 2 inputs (Right and Left for each input); or you can choose Multi-Channel, which will allow you to choose between 2 and 256 inputs.
Output Pins
Output
Audio signal pins are represented by a () circle, and traditional wiring is represented by a thin black line.
By default, the Automatic Gain Control component is set to a Mono channel, which provides 1 output. Additionally, you can set the Properties to allow for Stereo, which gives you 2 outputs (Right and Left); or you can choose Multi-Channel, which will allow you to choose between 2 and 256 outputs.
Schematic Example
In this example, we have the phone in our conference room routed through an Automatic Gain Control before reaching our Line Out component. The Automatic Gain Control will control the overall dynamic range of the Output when the Input level changes.
Properties
Automatic Gain Control Properties
Side Chain Input
Provides one Side Chain input per Channel. The Side Chain allows you to filter a signal before using it to control the Gain of the unfiltered audio Input.
In Gain is always applied to the Side Chain input signal, regardless of the state of Bypass.
Note: If you select Side Chain Input = Yes, and don't use the Side Chain Inputs, you will not have any AGC.
Detector Time
Sets one of four pre-set times, or enables the Detector Time control in the Control Panel. If one of the four pre-set times is chosen, the control is not available in the Control Panel.
Adjusts the time constant that determines the rate of change of the Detector level in response to changes in the Input signal. This adjustment is to prevent changes (spikes, low frequency signals) in the Input from causing unwanted, momentary output. A fast Detector Time may result in an Output that rapidly fluctuates.
Bypass Gain Meter
When set to Active, the Applied Gain meter is active regardless of the state of the Bypass button. This means you can adjust the AGC in Bypass mode.
When set to Inactive, the Applied Gain meter is inactive to indicate that the component is in Bypass mode.
Channels
Type (Channel)
Determines the Crossover Component's channel type - Mono, Stereo, or Multi-Channel. (Stereo = two mono channels)
Count (Multi-Channel)
When you choose Multi-Channel, you can specify from 2 to 256 for the Count.
Graphic Properties
Label
Use the Label property to change the name of the component in the schematic. The Label property defaults to the component name. To learn more about renaming schematic elements, see Organizing Your Design.
Position
The coordinates reference a specific place in the schematic - for example,"100,100" (horizontal, vertical). 0,0 is the upper left corner of the schematic.
Fill
Sets the fill color of the component in the schematic.
Script Access Properties
Code Name
Displays the currently assign name for control access. You can use the auto-assigned name or customize it. Q-SYS will automatically check all Code Names in the design to ensure name is unique.
Script Access
Defines whether the component will be accessible by script and/or externally, or not at all. Choices include All, External, None (default), and Script.
- None (default) - Not accessible by any script, plugin, or by Q-SYS Remote Control Protocol (QRC).
- Script - Can be accessed by scripts, such as Text Controller, Block Controllers, and plugins only.
- External - Can only be accessed by 3rd party controls systems using component commands from the Q-SYS Remote Control Protocol (QRC).
- All - No restrictions, can be accessed by 3rd party control systems via Q-SYS Remote Control Protocol (QRC), or script objects or plugin objects.
Tip: Use Script Programmer Mode to quickly view the Script Access setting directly on the component in the design schematic without the need to disconnect from the Q-SYS Core processor.
Controls
General Controls
In Gain (dB)
The Input Gain adds to the level of the Input source.
Detector (dB)
Graphically and numerically displays the RMS level of the highest Input.
Response Panel
Graphically represents the Gain Calculations for the Channel having the highest Input RMS level.
X axis represents the Input
Y axis represents the Output
The red dot represents the Output Level. Below the Threshold Level the Output is equal to the Input, above the Threshold level it is adjusted by the AGC.
Bypass
Bypasses the AGC functionality.
Applied Gain (dB)
Graphically and numerically displays the amount of Gain applied to the Channel with the highest RMS Input level. The same amount of Gain, calculated on the highest Channel, is applied to all other channels that are above the Threshold Level regardless of their relation to the Target Level.
Graphically the meter starts in the middle, displaying attenuation in red going down from center, and gain in green going up from center.
Out Gain (dB)
Controls the output level.
Gain Calculations
Threshold Level (dBFS)
The level at which the AGC Component becomes active. This should be set at a level so that the anticipated background noise does not activate the AGC. When an Input exceeds the Threshold Level, the Gain for that input is adjusted to calculated level based on the Ratio and the Target Level.
If there is more than one Input that exceeds the Threshold Level, the Gain is calculated using the Channel with the highest RMS level. The other Channel(s) have the same amount of Gain applied to them as the Channel with highest RMS Input level.
Ratio
The ratio between the Input and the Output as measured from the Target Level. The closer the Ratio is to 100, the closer the Output will be to the Target Level, which also means smaller dynamic changes in the Output level.
When the Input is below the Target Level and the Gain applied by the Ratio setting is greater than the Maximum Gain setting, the Output is clipped per the Maximum Gain setting.
Target Level (dB)
Sets the point from which the Gain is calculated based on the Ratio setting. Assuming only one Input, a level below the Target Level has a positive Gain applied, a level above the Target Level has a negative Gain (attenuation) applied.
If the
- Target Level is -15 dB
- Ratio is 2.5
- Input level is 10 dB
- Adjusted Output is
(((Input level - Target Level) / Ratio) + Target Level) = Output Level
((10 dB - (-15 dB) / 2.5) + (-15 dB)) = -5 dB
Maximum Gain (dB)
Sets the maximum amount of gain provided to an Input when the Input is above the Threshold Level, but below the Target Level. The Maximum Gain is not used when the gain applied by the Ratio setting is less than the Maximum Gain setting.
Ratio calculation used
- Threshold Level is -50 dB
- Target Level is -15 dB
- Ratio is 2 (2:1)
- Maximum Gain is 10 dB
- Input is -20 dB
- Adjusted Output is -17.5 dB
((( Input level - Target Level) / Ratio) + Target Level) = Output Level
((-20 dB - (-15 dB) / 2) + (-15 dB)) = -17.5 dB
The applied gain is 2.5 dB, which is less than the 10 dB Maximum Gain.
Maximum Gain used
- Maximum Gain is 10 dB
- Input is -40 dB
((( Input level - Target Level) / Ratio) + Target Level) = Output Level
((-40 dB - (-15 dB) / 2) + (-15 dB)) = -27.5 dB
would be a gain of 12.5 dB based on the Ratio - Adjusted Output is actually -30 dB a gain of 10 dB, which is equal to the Maximum Gain setting of 10 dB. The same calculation is used, but the Output is clipped at the Maximum Gain setting.
Time Constants
Detector Time (milliseconds)
Available only when Detector Time Property is set to Use Control.
Adjusts the time constant that determines the rate of change of the Detector level in response to changes in the Input signal. This adjustment is to prevent changes (spikes, low frequency signals) in the Input from causing unwanted, momentary output. A fast Detector Time may result in an Output that rapidly fluctuates.
Response Time (seconds)
Adjusts the time constant that determines the time it takes for the Gain to go from its current level to the new level when there is a change in the Input RMS level.
Hold Time (seconds)
When the Recovery button is engaged, Hold Time sets minimum time the applied Gain stays at the calculated level after the RMS Input level drops below the Threshold Level. This is to prevent the Output from fluctuating due to momentary pauses in the Input.
If there is another Channel in use with a lower RMS Input level, above the Threshold Level, the Hold Time does not apply. The applied Gain changes to the proper level for the new Channel based on the Response Time.
Recovery Time (seconds)
When the Recovery button is engaged, Recovery Time sets the time it takes for the applied Gain to return to zero.
If there is another Channel in use with a lower RMS Input level, above the Threshold Level, the Recovery Time does not apply. The applied Gain changes to the proper level for the new Channel based on the Response Time.
Recovery Enable
Turns on and off the Recovery Time Enable functionality. In the Off position, the Hold Time and Recovery Time do not apply.
If there is only one Channel above the Threshold Level, and the Recovery button is in the Off position, when that Channel drops below the Threshold Level, the Gain stays at the last calculated level before the Channel dropped below the Threshold Level.
Control Pins
The available Control Pins depend on settings in Properties.
|
Pin Name |
Value |
String |
Position |
Pins Available |
|---|---|---|---|---|
|
Applied Gain |
-20 to 20 |
-20 dB to 20 dB |
0.000 to 1.00 |
Output |
|
Bypass |
0 1 |
active bypass |
0 1 |
Input / Output |
|
Detector Level |
-100 to 20 |
-100 dB to 20 dB |
0.000 to 1.00 |
Output |
|
Detector Time |
0.100 to 60 |
100 ms to 60 s |
0.000 to 1.00 |
Input / Output |
|
Hold Time |
0.000 to 10 |
100 ms to 10 s |
0.000 to 1.00 |
Input / Output |
|
Input Gain |
-20.0 to 20.0 |
-20.0 dB to 20.0 dB |
0.000 to 1.00 |
Input / Output |
|
Maximum Gain |
0.000 to 20.0 |
0 dB to 20.0 dB |
0.000 to 1.00 |
Input / Output |
|
Output Gain |
-20.0 to 20.0 |
-20.0 dB to 20.0 dB |
0.000 to 1.00 |
Input / Output |
|
Ratio |
1.00 to 100 |
1.00 to 100 |
0.000 to 1.00 |
Input / Output |
|
Recovery |
0 1 |
active bypass |
0 1 |
Input / Output |
|
Recovery Time |
0.100 to 10 |
100 ms to 10 s |
0.000 to 1.00 |
Input / Output |
|
Response Time |
0.100 to 10 |
100 ms to 10 s |
0.000 to 1.00 |
Input / Output |
|
Target Level |
-60 to 20 |
-60 dB to 20 dB |
0.000 to 1.00 |
Input / Output |
|
Threshold Level |
-60 to 20 |
-60 dB to 20 dB |
0.000 to 1.00 |
Input / Output |
