Trident 500 Series - Lo-Cut Filter Functionality; The Lo-Cut Filter; Lo-Cut Dynamic Tracking

3 Trident Audio Developments | Hi-Lo Dynamic Filtering User Manual 4
Hi-Cut Dynamic Tracking continued
A LOW-CUT ENABLE switch allows each individual frequency band or
filter to be assessed,
while a red PEAK warning indicator will illuminate
at approximately +16dBu, approximately 12dBu below clip-ping. To allow
adequate headroom, avoid boosting the signal by more than an amount
which just causes this LED to flash on occasional peaks.
Lo-Cut Dynamic Tracking
Using the TRACK SIGNAL function, enables the Lo-Cut filter to be used
for dynamic hum or rumble reduction. This is a technique which relies on
the psychoacoustic eect of ‘masking’, in which a louder signal will cover
up a quieter signal of the same frequency. In this mode, the cut-o fre-
quency tracks dynamically the low frequency content of the music, with
the FREQUENCY control setting the frequency to which the filter will
open up in the absence of any low frequency content.
With a noisy signal applied (e.g. from a record deck or other material with
a high background noise content), start with the FREQUENCY control at
minimum (fully anticlockwise) and advance the control until the hum or
rumble just disappears.
In practice, this technique demands a trade-o between noise reduction and loss
of some low frequency content of
the program material. However,
using the steepest (24dB
per
octave) slope, maximises the
amount of low frequency content
retained. In addition, discreet
use
of the RESONANCE control
to
introduce a small peak of a
few
dB at the cuto frequency,
can
psycho acoustically enhance
the
apparent bandwidth of the
filtered signal. Use of higher
resonant settings will result
in
the movement of the filter
becoming audible and indeed,
combined with higher settings
of the FREQUENCY control, this can
be the basis of some
unique eects.
Use of higher resonant set-
tings will result in the move-
ment of the filter becoming
audible and indeed, combined
with the lower settings of the
FREQUENCY control, this can
be the basis of some unique
special eects.
Further possibilities —
The sweep range of the Hi-Cut
filter is extremely wide, from
effectively subsonic, right up
to full audible bandwidth. This
suggests the possibility of fad-
ing tracks in and out, not in the amplitude domain as is usual, but in the
frequency domain.
The Lo-Cut
This is a sweepable high pass filter with unity
gain in the selected pass band and selectable
(12dB per octave or 24dB per octave) roll-o
outside of the pass band. Cuto frequency can be
set manually, anywhere from 15Hz to 16kHz.
In addition, a RESONANCE control can be
switched into the circuit, to introduce a resonant
peak at the selected cuto frequency. The
size of this peak, which is dependant on the
elected frequency selected on the front panel,
can be varied from zero to approximately +12dB.
At maximum setting, RESONANCE stops just
short of self-oscillation.