BSS Audio DPR-402 Owner's Manual - Manual (Page 32)

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15.0 Applications using the Barrier Strip
Control Side Chain
A very common requirement is to make the threshold of the compressor
frequency conscious by inserting a graphic or parametric equaliser into the
control side chain. The input of the external equipment should be connected
to one of the send outputs of the unit, and the output of the external
equipment connected to one of the return inputs, as required. Care should be
taken to avoid introducing earth loops when the external equipment is mains
powered, as all inputs and outputs on the barrier strip are unbalanced. A signal
0v ground is provided at pins A and J for connection to the screens of one or
both of the connecting cables, as neccesary.
All external equipment should be capable of operating at general line levels
(Max +20dBv), have unity gain, and have high input impedance (>10k) and a
low output impedance (>1k).
In order to preserve the THRESHOLD control calibration, it is essential that
unwanted frequencies are attenuated rather than wanted frequencies boosted
by the external filter. For example, if compression is to be controlled by a
narrow mid-band of frequencies, then the low frequency and high frequency
sliders should be pulled down, and the mid-band sliders left at 0dB.
15.1 Patching of
External Equipment
Subtracting Side Chain
Inserting an external equaliser into the subtract side chain has the effect of
modifying the tonal balance of the processed signal by adding or subtracting a
specific band of frequencies. The external equipment should meet all the
requirements specified in the control side chain section (above) and be
operated in a similar manner. The adding or subtracting process requires that
all signals are appropriately phased and the gain be unity. Any errors may
lead to unexpected results. Figure 15.1 shows a typical transfer response
obtained because of the phase shift associated with standard filters.
For the units DE-ESS HF function, the internal filters have been phase and
amplitude corrected to achieve the required response.
Fig 15.1
Uncompensated
External Filter in
Subtract Side Chain
Barrier Strip Applications