Based on the Portico 5017 Mobile Pre, the 517 provides world-class transformer-coupled micpreamp, compressor and DI circuitry with Vari-phase, “Silk” and DI/mic blending capabilities – all in a single 500 series module.

Compression
For signals below the “threshold” level that has been set, a compressor provides a linear path allowing signals to be amplified without the gain being adjusted in any way. When signals exceed the “threshold” level, the gain is reduced in a controlled manner that depends on the Ratio that has been set.
Gain
GAIN range provided is from -6dB to +20 dB. As already noted, when compression has taken place, it may be necessary to increase the overall gain to restore the apparent program level
Peak
When engaged, the 543 uses a combination of peak and RMS (average) detection to determine level. When disengaged, it follows just RMS.
SC HPF
Introduces a HPF at 250Hz to the VCA side chain signal. This allows the compressor to disregard sustained low frequency content.
Ratio
Range from 1:1 to LIMIT (i.e. 40:1)
Threshold
Range from -30dBu to +20dBU
Attack Time
Range from 20 mS to 75 mS.
Release / Recovery Time
Range of RELEASE time is 100 mS to 2.5 Seconds.
Stereo Operation
When the LINK switch is engaged on two 543 modules and settings are approximately the same values, GAIN reduction on both channels will be the same to preserve stereo balance and position. This will work properly in link buss enabled 500 series racks, or by hardwiring two 543 modules link busses together in non-compatible racks.
Ducking
When the LINK switch is engaged on two connected 543 modules, the signal passing through the first module may be used to control the amplitude of a second module. For example, the level of music through channel A can be controlled by speech on channel B, i.e. reducing the music level to make a “speech-over” announcement.
Meters
Two Peak LED METERS are provided that show OUTPUT LEVEL and GAIN REDUCTION.
Output level meter covers the range from -10 to +22 dBu and above which is regarded as overload.
REDUCTION is calibrated in dB covering the range +1 to 22 dBu, reading from right to left,