Introduction
The legendary A-Range® equaliser holds a unique place in audio history, with a
stunningly musical sound that resulted from its all-discrete transistor circuitry and
the use of inductors in the upper and lower mid bands. The A-Range® s a faithful
re-creation of the original four band Trident A-Range® equaliser in a 500 module
format, that will add the unique Trident signature to any programme material.
The mid frequency EQ sections are “peaking”, while the high and low frequency
sections are “shelving”. A distinguishing feature of both the original A-Range® console
and this module, is the use of faders for level adjustment, rather than rotary potentiometers.
These faders feature a useful centre detent at mid travel to denote zero boost or
cut of the selected frequency. The use of faders makes it very easy to see not only
how much equalisation is being applied. Each band is rotary-switch-selectable to
one of four frequencies, while individual push buttons engage the three high pass
and three low pass filters. An LED peak level indicator is included to warn when
levels get too high. The Line level input and output are balanced for maximum
signal integrity & high output levels with minimum distortion.
The difference between shelving and peaking equalisers are as follows. A shelving
equaliser boosts or cuts all frequencies equally, above or below a certain frequency,
usually the point where it effectively reaches its “shelf” state. A “high shelf” EQ
boosts or cuts high frequencies and a “low shelf” type boosts or cuts low fre-
quencies. This type of circuit is very popular in hi-fi systems but is also actually
highly musical when applied in a recording environment. In contrast, a peaking
equaliser is one that, as its name implies, has a centre frequency that is boosted
or attenuated more than others. The frequency range over which it reaches its
peak and then falls down is known as the bandwidth (or “Q”). Because this type
of design reaches a peak and then falls away, it is possible with this type of circuit
to “home in” on particular frequencies and make adjustments without affecting
those around them. This can be particularly useful when working with instruments
such as bass guitars and snare drums. By incorporating both shelving and peaking
equalisers into the design of the versatile A-Range®, it is possible to get the best
of both types of design.
Operating the Equaliser
Begin with all boost/cut faders set to their mid way (‘0’) positions. Adjust the low
and high mid frequency controls to their minimum positions (fully anticlockwise).
The high and low pass filter switches should be in their out positions. Set the fre-
quency select switchescontrolling the high and low shelving sections, to 150Hz and
12kHz respectively. Lastly,press the ‘IN’ switch (the associated green LED will light).
Pushing up any of the four faders beneath its associated frequency select switch,
will result in the chosen frequency being boosted. Moving the faders below cen-
tre will result in the chosen frequency being cut. Operating the frequency select
switch in the high section (8kHz to 15kHz shelving) will introduce a subtle change
of emphasis. Operating the frequency select switch in the upper mid section (3kHz
to 9kHz peaking) will introduce a distinct difference according to the frequency
selected, since it is now peaking rather than shelving and also due to the charac-
teristics of the inductor-based circuitry. Operating the frequency select switch in
the ‘lower mid’ section, 250Hz to 2kHz peaking, will also introduce a distinct differ-
ence according to the frequency selected, again because of its peaking nature and
the use of inductors in this part of the circuit.
Operating the frequency select switch in the low section, 80Hz to 150Hz shelving,
will introduce an effective change of emphasis to the low frequencies.
Finally, the three shelving ‘low-pass’ and ‘high-pass’ filter sections are employed to
introduce a roll-off of either high frequencies or low frequencies respectively, ac-
cording to which of the three push buttons are selected in each section. The high-
pass filters are useful for the minimization of extraneous low frequency ‘rumble’
caused, for example, by someone’s feet moving about near a microphone stand,
nearby traffic noise, AC systems, etc. Additionally, a high-pass filter can be used
effectively during recording to reduce the accumulation of low frequency sounds
that can adversely affect a mix. The three high-pass corner frequencies are 25Hz,
50Hz and 100Hz. The low-pass filters are used to minimize high frequency noise
that may cause ‘harshness’ in a vocal, or to tame the output of a violin or guitar
amplifier, etc. Low-pass filtering is often employed on kick and snare drums and
bass guitars, as well as a means of reducing ‘hiss’. The three lowpass filter frequen-
cies on the A-Range® are 9k, 12k and 15k. Filters can also be used in combination
for greater effect.
The amount of boost or cut required for any particular programme material is a
very subjective matter and is usually found by experiment. Use the ‘IN’ switch to
make comparisons between EQ’d and non-EQ’d signals. Keep an eye on the red
“PK” LED: occasional flashes are OK but if it is on all the time, turn down the input level
to the A-Range® module. using whatever modules precede it in the signal chain.
Extended Function
If you have a Radial Workhorse™ or compatible rack, you can send the output of
the A-Range® to the rack’s internal mix buss. To do this, locate jumper J1 on the
main circuit board near the edge connector. Move the jumper onto the two pins
nearest R53.
Technical Specification*
Input impedance
10kohm balanced
Common mode rejection
70dB
Equivalent input noise
-85dBu (unweighted,
no
boost
or
cut)
Distortion
0.05% (+4dBu output, 1kHz)
Frequency response
20Hz to 20kHz (-1dB)
Boost / Cut range
+/-15dB (variable)
Filter Q value
1.3 (1 octave)
Maximum input level
+22dBu
Max output before clip
+28dBu (10k load)
Nominal output level
+4dBu (electronically balanced)
Output impedance
100 ohm
Output noise floor
-85dBu (typical, unweighted)
Peak LED threshold
+16dBu
I/O connections
XLR: pin 2 +, pin 3 -, pin 1 ground
Current requirement
130mA (maximum) per rail
*In the interests of product development, Trident Audio Developments
may change technical specifications without notice.
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Trident Audio Developments
| A-Range® 500 User Manual
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Trident Audio Developments
| A-Range® 500 User Manual
