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FM-531HD / May 2013
F M - 5 3 1 H D P R O G U I
The automatic gain control (AGC) itself operates in five frequency bands, and its
medium‑term operation is a special derivative of the type of program‑related processing
occurring in the Compressor algorithms. While the SST section operates in Left/Right
mode, the AGC and Compressors operate on the program content’s Sum and Differ‑
ence – the highest signal, whether it’s in the sum or difference channel, determines the
amount of processing to be applied to both channels.
SST Controls Overview
SST Drive
The SST Drive control adjusts the amount of signal fed to the algorithm that mea‑
sures the dynamic behavior of the five band AGC. The higher the SST Drive setting the
deeper the control depth in the algorithm – which allows it to operate over the widest
possible program dynamic range.
A typical amount of SST control depth that affords the best tradeoffs in operation
will be somewhere between ‑12 and ‑15dB as seen on the gain reduction display. Note
that there is no harm in generating more or less control depth as long as one understands
that more control depth affords greater long term control of audio levels and less control
depth affords less. The overall control range is +30.0dB to +40.0dB.
SST Gate Threshold
The SST algorithm has been provided its own Gate Threshold so that its operation
may be optimized when it is combined with the five band AGC. Typically the SST Gate
Threshold will be set several dB higher (less negative) than that of the five band AGC.
The overall control range is ‑60.0dB to ‑35.0dB.
The SST Gate Threshold control sets the audio input level where SST correction is
turned off and its gain is frozen.
Ramp Rate
In order for the SST to behave with all types of program requirements it must have
its speed of correction tailored for the application and this is what the Ramp Rate control
does. The control is calibrated in units of time, and therefore describes the rate at which
the SST causes more or less activity to occur within the five band AGC/Compressor.
A good typical starting value for SST Ramp Rate is 4.000 seconds. The full control
range is 2.000 to 7.000 seconds.
Summary of Contents for FM-531 HD
Page 2: ...Technical Manual Wheatstone Corporation May 2013 FM HD Digital Audio Processor FM 531hd...
Page 122: ...page A 2 FM 531HD May 2013 A P P E N D I C E S Appendix A General Specifications A 3 Contents...
Page 128: ...page A 8 FM 531HD May 2013 A P P E N D I C E S Appendix B FM 531HD GPI Interface A 9 Contents...
