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.
Warranty - This product is warranted free from defects in material or workmanship,
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-
turned, freight prepaid, in its original or similarly protective packaging, to a Trident
Audio Developments Service Center. Trident Audio Developments is not obligated
to provide the Purchaser with a substitute unit while repairs are carried out.
Environmental - This product complies with the RoHS directive and contains no
lead or other banned hazardous materials. In accordance with the WEEE directive,
this product must be disposed of responsibly at its end of life, by means of local
authority approved recycling systems.
For further information, or to register your purchase,
visit: www.tridentaudiodevelopments.com
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1845 W 169th Street, Gardena, CA 90247 | tridentaudiodevelopments.com
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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
Based on the CLM
Dynamics DB500
Expounder, Trident
Audio Developments have
brought to life the adaptive
filtering circuitry that
made the original a
classic, in a modern
500 series format.
—————————————————————————————————————————————————
Branded the Hi-Lo, the Trident 500 series Hi-Lo is an adaptive Hi-Cut /
Lo-Cut frequency filtering module which can respond dynamically to the
program material, providing the user with 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 selectable (12dB per octave or 24dB per octave) roll-o out-
side the pass band. Cut o frequency can be set from 75Hz to 24kHz.
In addition, a RESONANCE control can be switched into circuit, to intro-
duce a resonant peak at the selected cut-o frequency. The size of this
peak, which is independent of the selected cut-o frequency, can be var-
ied from zero to approximately +12dB. At maximum setting, RESONANCE
stops just short of self-oscillation.
A HI-CUT ENABLE switch allows each individual frequency band or filter
to be assessed, whilst a red PEAK warning indicator will illuminate at ap-
proximately +16dBu, approximately 12dBu below clipping. To allow ad-
equate headroom, avoid boosting the signal by more than an amount
which just causes this LED to flash on occasional peaks.

3Trident Audio Developments | Hi-Lo Dynamic Filtering User Manual 4Trident Audio Developments | Hi-Lo Dynamic Filtering User Manual
Hi-Cut Dynamic Tracking continued
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.
The Lo-Cut
This is a sweepable high pass filter with unity
gain in the selected pass band and select-
able (12dB per octave or 24dB per octave)
roll-o outside of the pass band. Cut o fre-
quency can be set manually, anywhere from
15Hz to 16kHz.
In addition, a RESONANCE control can be
switched into circuit, to introduce a resonant
peak, which is independent of the selected
cut-o frequency, which can be varied from zero
to approximately +12dB. At maximum set-
ting, resonance stops short of self-oscillation.
A LOW-CUT ENABLE switch allows each indi-
vidual frequency band or filter to be assessed,
whilst a red PEAK warning indicator will illuminate at approximately
+16dBu, approximately 12dBu below clip-ping. To allow adequate head-
room, avoid boosting the signal by more than an amount which just caus-
es 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
min-imum (fully anticlockwise) and advance the control until the hum or
rumble just disappears.
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
eectively 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.
Connecting two Hi-Lo filter modules in series, via an external linking system
such as on the Trident Deca Dent, permits filter slopes of up to 48dB per
octave to be realised(!).

3Trident Audio Developments | Hi-Lo Dynamic Filtering User Manual 4Trident Audio Developments | Hi-Lo Dynamic Filtering User Manual
Lo-Cut Dynamic Tracking continued
In practice, this technique de-
mands 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 cut-o 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 be-
coming audible and indeed,
combined with higher settings
of the FREQUENCY control, this
can be the basis of some unique
eects.
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 sug-gests the possibility of fading tracks in and out, not in the ampli-
tude domain as usual, but in the frequency domain.
Again, connecting two Trident Hi-Lo modules in series, via an external
linking system such as on the Trident Deca Dent, permits filter slopes of
up to 48dB per octave to be realised(!).
Dynamic Linking Linked Stereo Tracking
Two Trident Hi-Lo modules can be employed for linked stereo tracking,
when used via an external stereo linking system, such as on the Trident
Deca Dent.
This is achieved by enabling both Hi-Lo modules TRACK SIGNAL switches
and setting the FREQUENCY controls to identical positions. The track signal
is generated by the sum of the left and right signals, and the automatic tracking
follows both the left and right signal sources.
— 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