dbx 160X - Page 15

OPERATING NOTES
dbx Professional Products
While it is true that all frequencies are lowered in level when the compres¬
sor is triggered, generally the “sss” sound occurs alone, before or after
the dominant tone in the voice.
Increasing sustain
To increase the sustain of a musical instrument (e.g., a guitar or bass),
use an equalizer in the level detector circuit and boost the EQ in the domi¬
nant frequency range of the instrument, along with a fairly low threshold
and a moderate compression ratio.
Using a Filter in the Level Detector Circuit
The results of inserting a filter in the level detector circuit are basically the
same as obtained with an equalizer, as previously described. Those fre¬
quencies passed by the filter are subject to compression (or at least they
are subject to considerably more compression than those frequencies out¬
side the passband). Because a passive filter can have insertion loss, it
may be necessary to lower the 160XT’s THRESHOLD setting to maintain
a given amount of gain reduction within the filter passband; this can be de¬
termined by monitoring the 160XT’s threshold indicator LEDs.
Multi-way speaker systems.
If a single compressor is to be used with a multi-way speaker system (i.e.,
before the crossover, after EQ), the system operator is faced with the
problem of keeping levels below the point of destruction of the most sensi¬
tive part of the system. If, for example, mid-range drivers are frequently
damaged, the whole system must be operated at a lower sound-pressure
level, or additional mid-range drivers must be added. By inserting an
equalizer in the detector path to the 160XT, it can be made more sensitive
to frequencies in the range handled by the sensitive drivers. The system
can then be run at higher levels and will only be dropped back when dam¬
aging signals are present.
Pre-emphasis for broadcast applications
By inserting a pre-emphasis filter network in the detector path of a 160XT
processing pre-emphasized audio, higher levels can be run within the
headroom limitations of the broadcast chain.
Anticipated Compression
By feeding the program directly to the 160XT’s detector input and sending
the audio signal through a delay line before the audio input, the unit can
anticipate the need for a gain change. See figure 7. With some experimen¬
tation, the effect can be that of zero attack time at a given frequency. Addi¬
tional signal delays beyond this zero time will then cause the compressor
to finish reducing the gain before the leading edge of the loud passage
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