Trident 500 Series User manual

DYNAMIC RESONANCE ADAPTIVE TRACKING FILTER
Hi-Lo Dynamic Filtering User Manual
Safety - This product is intended for professional use only and it is assumed
that the user is familiar with the 500 Series Modular Rack system. Always
switch o the rack power before inserting or removing this (or any other)
module or damage may occur. Do not expose this product to direct heat,
moisture or mechanical shock.
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for a period of one year from date of purchase. During this period, Trident Au-
dio Developments will repair or replace this product by prior arrangement free
of charge, providing the product is determined to be defective and has been re-
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1Trident Audio Developments | Hi-Lo Dynamic Filtering User Manual 2Trident Audio Developments | Hi-Lo Dynamic Filtering User Manual
Trident
500 Series
Hi-Lo
Dynamic
Filtering
No Ordinary
Filtering
—————————————————————————————————————————————————
The Trident Hi-Lo, an adaptive Hi-Cut/Lo-Cut frequency filtering module
that responds dynamically to program material, providing a high degree
of control and signal enhancement, unavailable in any modern day 500
series package.
—————————————————————————————————————————————————
— OVERVIEW —
The Hi-Cut
This is a sweepable low pass filter with unity
gain in the selected pass band and a select-
able (12dB per octave or 24dB per octave) roll-
o outside the pass band. Cuto frequency
can be set from 75Hz to 24kHz.
In addition, a RESONANCE control can be
switched into circuit, to introduce a resonant
peak at the selected cuto frequency. The size
of this peak, which is dependant on the elect-
ed frequency selected on the front panel, can
be varied from zero to approximately +12dB.
At maximum setting, RESONANCE stops just
short of self-oscillation.
A HI-CUT ENABLE switch allows each individ-
ual frequency band or filter to be assessed, while a red PEAK warning indi-
cator will illuminate at approximately +16dBu, approximately 12dBu below
clipping. To allow adequate headroom, avoid boosting the signal by more
than an amount which just causes this LED to flash on occasional peaks.
Hi-CUT Dynamic Tracking
Using the TRACK SIGNAL function enables the Hi-Cut filter to be used
for dynamic noise 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 cuto frequency
tracks dynamically the high
frequency content of the music, with the FRE-
QUENCY control setting the frequency to which the filter will close down
in the absence of any high frequency content.
With a noisy signal applied (e.g. from analogue tape or other material
with a high background noise content), start with the FREQUENCY con-
trol at maximum (fully clockwise) and back o the control until the noise
just disappears.

3Trident 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.

5Trident Audio Developments | Hi-Lo Dynamic Filtering User Manual 6Trident Audio Developments | Hi-Lo Dynamic Filtering User Manual
Lo-Cut Dynamic Tracking continued
Further possibilities — The sweep range of the Lo-Cut filter is extremely
wide, from eectively ultrasonic to right down to full audio bandwidth.
This suggests the possibility of fading tracks in and out, not in the ampli-
tude domain as usual, but in the frequency domain.
Hi-Lo Peak Indicators
The Trident Hi-Lo includes LED peak indicators on the outputs of both
the Hi-Cut filter section and the Lo-Cut filter section. Since the filters are
in series (the Hi-Cut circuitry before the Lo-Cut), the Hi-Cut Peak LED
monitors the Hi-Cut filter stage only, and the Lo-Cut Peak LED monitors
signal thru both stages, and as such, the output of the unit. This gives the
most flexibility for clip monitoring in the unit. The Output of the Hi-Lo
can drive approximately 27.5 dB into a 600 Ohm load. The clip levels are
approximately 12 dB below actual signal Clip (so we have this occur at
+16dBu) and allows for tweaks in resonance which may exceed that but
allow for headroom after the clip indicator has just reached active.
It should also be noted, that if neither the Hi-Cut or Lo-Cut switches are
enabled, the peak LED indicators are actively monitoring the incoming
signal level.
Dynamic Linking Linked Stereo Tracking
The Trident Hi-Lo module also oers the option of linked stereo tracking
when paired with a second Trident Hi-Lo module. Ordinarily, most 500
Series racks oer paired slots by default. The Trident Hi-Lo provides an
on-board stereo link switch (S9) for use in this instance. With both mod-
ules stereo link switches selected to on, and the modules fitted in the pre
paired slots, the modules are now paired together.
By enabling both Hi-Lo modules TRACK SIGNAL switches, and setting
the FREQUENCY controls to identical positions, the left and right signals
are now summed together, and the automatic tracking follows both the
left and right signal sources.
When using a 500 Series rack with selectable stereo pairing on the rear
of the rack, such as with the Trident Deca-Dent, by releasing the on-board
stereo link switches, both modules can be used as separate mono units
without the need to access the rear of the rack.
API Radial Workhorse
An on-board jumper is available for use when the Trident Hi-Lo is used in
conjunction with the API Radial Workhorse. When selected, this allows the
Hi-Lo to send its output to the Workhorse mix bus (pin 11), which is fed to
the Workhorse mixer section. This can be used in conjunction with the on-
board stereo link switch, thus enabling stereo use on the Workhorse.
— SPECIFICATIONS —
Input Impedance 10 kilohms
Max Input +27dBu
Max Output +27dbu (Into 600ohms)
Distortion (+10dBu Out) 0.0031% (20Hz to 20kHz)
(Hi Enabled Max Freq)
(Lo Enabled Min Freq)
Distortion (+20dBu Out) 0.0069% (20Hz to 20kHz)
Frequency Response 15Hz to 60kHz (-3dB)
Noise (20Hz to 20kHz bandwidth limited)
No Filters in circuit (Residual Noise) -95dBu
High Cut Enabled
Freq Max -83.5dBu
Freq Min -90dBu
Freq Max – 24dB/Oct Slope Enabled -80dBu
Freq Min – 24dB/Oct Slope Enabled -90dBu
Freq Max – Res Enabled, Resonance Min -83.5dBu
Freq Max – Res Enabled, Resonance Max -72dBu
Freq Max – 24dB, Res Enabled, Res Max -71dBu
Freq Min – Res Enabled, Resonance Min -90dBu
Freq Min – Res Enabled, Resonance Max -90dBu
Freq Min – 24dB, Res Enabled, Res Max -90dBu
Low Cut Enabled
Freq Max -83dBu
Freq Min -86dBu
Freq Max – 24dB/Oct Slope Enabled -83dBu
Freq Min – 24dB/Oct Slope Enabled -90dBu
Freq Max – Res Enabled, Resonance Min -84dBu
Freq Max – Res Enabled, Resonance Max -72dBu
Freq Max – 24dB, Res Enabled, Res Max -73dBu
Freq Min – Res Enabled, Resonance Min -86dBu
Freq Min – Res Enabled, Resonance Max -87dBu
Freq Min – 24dB, Res Enabled, Res Max -84dBu
Up to 48dB Per Octave Slope (Wired In Series)
When two Hi-Lo modules are connected in series, slopes of 12, 24, 36 and
48dB can be achieved, in any combination, by selecting the appropriate
SLOPE buttons on the front of each Hi-Lo module. For example, by en-
gaging both of the Hi-Lo modules Hi-Cut filters, and setting both mod-
ules to 24dB slope, the program material will be subject to a 48dB slope.
By adjusting one of the Hi-Cut filters to 12dB, the program material will be
subject to a 36dB slope.
The introduction of a third Hi-Lo in series with the first two Hi-Lo mod-
ules, would provide for yet steeper slopes, again in increments of 12dB. If
fact, because they can be connected in series, you’re only limited by the
number of Hi-Lo’s that you have to hand.