BSS Audio DPR 504, User Manual

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Control operations Control operations Control operations Control operations Control operations
7.1 Filter and Width
Operating Instructions
These two controls adjust the internal key side-chain filters, and a set of
response curves are given in
figure 7.1 . These filters are used to control the
frequency content of the signal being sent to the gate control circuitry and
allow the filtering-out of information not required to control the gating action.
They are not placed in the main signal path, and therefore have
no
effect
whatsoever on the program material. In use, the filters should be considered as
a pair of tracking high pass and low pass filters, with the space between them
controlled by the
width control. Thus it is possible to achieve a variety of key
side-chain filter responses from a very broad filter set giving a wide band
response, to a quite narrow set for a very selective response.
The frequency scaling around the key filter control knob is the approximate
value for the centre of the response, without regard to the octave value set by
the width control. In use, the user should commence with a fairly wide width
setting, and then progressively narrow the response down whilst sweeping the
frequency to isolate the dominant frequency of the program, thus rendering
the
threshold control sensitive only to the required signal.
This type of filter realisation not only allows band-pass filter configurations,
but also the conventional low pass or high pass configurations by the
appropriate setting of the
key filter
and
width
control. Experience will show
that this approach gives considerable operational advantages for the user over
the more elementary separate low/high pass filter approach.
In application, the frequency response of the filter is set to coincide with that
of the signal to be gated, or a smaller but stronger part of it that is always
present. This will ensure for example, on microphone signals, that out of band
information close in level to the required signal will not cause spurious
openings of the gate. Should this facility not be required then the controls
should be set as indicated in the
section 6.0 .
7.0 Operating instructions