Symetrix 528 - Parametric EQ in the Sidechain; Usiq Sidechain EQ to Enhance Expander Action

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Step 4. Increase aain aaain to find the third most prominent feedback
frequency. Repeat Step 2 usina yet another of the EQ sections.
Step S. Reduce system gain to normal operating levels.
4.7 Parametric EQ in the Sidechain
The EQ/Notch Filter can be placed in the sidechain of the dynamic range processor to
make compression, limiting, or expandina action frequency sensitive. The equalizer is
patched into the sidechain, so the audio signal that will ultimately become the VCA's
control voltaae can be equalized before beina fed to the detector circuitry (see Section
1.10).
If the 528 has been wired to a patch bay, interconnect:
1. C/L-EXP SIDECHAIN OUT to EQ IN
2. EQ OUT to C/L-EXP SIDECHAIN IN
3. CL-EXP OUT to LINE DRIVER IN
If the unit has not been wired to a patch bay, the shortina connectors between terminals
9/10 on barrier strip TBl, and 1/ 2 and 4/5 on barrier strip TB2 must be removed. Then ,
connect:
1. TBl/9 to TB2/2
2. TB2/4 to TBl/10
3. TB2/l to TB2/5
To make the 528's comp/limiter more sensitive to hiah frequencies, boost the hiah
frequencies on the equalizer. This increases the sensitivity of the control circuits to
those particular frequencies, so the comp/limiter responds more to those frequencies than
any others. If the offendina frequencies produce a control signal of greater amplitude
than the desired frequencies, they will control how the comp/limiter behaves with the
rest of the signal as well. However, if the offendina signals are of significantly greater
amplitude than the rest of the signal, careful adjustment of the COMP THRESHOLD
(combined with the boost provided by the EQ in the loop) will make the comp/limiter
respond only to the boosted frequencies.
Keep in mind that the COMP THRESHOLD becomes a function of the amount of overall gain
throuah the equalizer , including the boost. This technique can be used with any
frequency that can be controlled by the equalizer.
Cuttina a frequency will create the inverse effect, making the 528 Jess sensitive to
frequencies that are cut from the control signal.
4.8 Us in g Si dechain EQ to Enhance Expander Action
Since the expander can only discriminate between different levels (not different sounds),
it can be fooled by signals whose levels are nearly the same, even if the frequency
content of those signals is fundamentally different. When the 528's expander is used to
shut out unwante d sounds, any signal that exceeds threshold will trigger the expander.
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