XTA G2 User manual

Page 2G2 Operators Manual
G2 Quick Reference
THINGS YOU NEED TO KNOW…
üBOLD MEANS HOLD!
Any functions that would produce possible
unexpected level changes at the outputs are
protected by a ‘press and hold’ action and
printed in BOLD on the panel. These functions
are:
Changing MODE between Gate and Expander;
Enabling the sidechain LISTEN function;
Ganging the two channels together in STEREO
mode.
üThe main meters show level, in dB, from
the clipping point of the input of the unit
just after the analogue to digital
converter stage. As the unit is unable to
add any gain to the signal, there is no
need for an output meter.
üWhen in Expander mode, the Hold knob
has no effect.
üRemember that you won’t hear the
effect of the parametric sidechain band,
unless there is cut or boost applied –use
the GAIN switch to cycle through the
levels.
üThe Listen LED always flashes when
Listen is enabled. Listen is automatically
turned off if the unit is switched off and
on.
üRemember that the Range/Ratio control
applies to both modes of operation –the
values in the boxes are for Gate mode,
and are in dB, the other values are ratios
for Expander mode.

G2Operators Manual Page 3
Contents
G2 Quick Reference 2
Important Safety Information 4
Thanks 5
Unpacking the G2 5
Introduction 6
Features 6
Front Panel Familiarisation 7
Rear Panel Connections 9
Operating the G2 10
Switching the unit on and start-up procedure 10
Press-and-hold Keys 10
Minimum and maximum control positions 10
Noise Gate Know-how 11
Attack and Release Times. 11
Setting the Range Correctly. 13
Using the Hold Time. 13
Expanders and Expansion –the subtler approach 15
What does an Expander do? 15
Why are Expanders necessary? 15
How does a Expander work? 16
What is the difference between an Expander and a Noise Gate? 18
Sidechain Equalisation –How and When to Use it 19
When would Sidechain EQ be useful? 19
How would sidechain EQ normally be implemented? 19
Picking out instruments for gating. 19
Look Ahead Delay –Pre-emptive Action 21
Setting the Attack and Release times 24
Gate and Expand MODE 25
STEREO Linking 25
Operating Notes 26
Operating Level 26
Grounding 26
Specifications 27
Warranty 28
Options and Accessories 28

Page 4G2 Operators Manual
An example of this equipment has been tested and found to comply with
the following European and international Standards for Electromagnetic
Compatibility and Electrical Safety:
Radiated Emissions (EU): EN55013-1 (1996)
RF Immunity (EU): EN55103-2 (1996) RF Immunity, ESD, Burst Transient,
Surge, Dips &Dwells
Electrical Safety (EU): EN60065 (1993)
Important Safety Information
Do not remove Covers.
No user serviceable parts inside, refer servicing to qualified service personnel.
This equipment must be earthed.
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
DO NOT EXPOSE TO RAIN OR MOISTURE
ATTENTION
RISQUE DE CHOC ELECTRIQUE
NE PAS ENLEVER
NE PAS EXPOSER A LA PLUIE NI A L’HUMITE
It should not be necessary to remove any protective earth or signal cable shield connections.
Do not defeat the purpose of the polarized or grounding-type plug. A polarized plug has two
blades with one wider than the other. A grounding type plug has two blades and a third
grounding prong. The wider blade and the third prong are provided for your safety. When the
provided plug does not fit into your outlet, consult an electrician for replacement of the obsolete
outlet.
Only use this equipment with an appropriate mains cord.
In the USA the cord should comply with the requirements contained in the Standard for Cord
Sets and Power Supply Cords, UL 817, be marked VW-1, and have an ampacity rating not less
than the marked rating of the apparatus.

G2Operators Manual Page 5
Thanks
Thank you for choosing the XTA G2 Dual Gate/Expander for your application.
Please spend a little time reading through this manual, so that you obtain the best
possible performance from the unit.
All XTA products are carefully designed and engineered for cutting-edge
performance and world-class reliability. If you would like further information about
this or any other XTA product, please contact us.
We look forward to hearing from you in the near future.
Unpacking the G2
After unpacking the unit, please check it carefully for any damage. If any is found,
immediately notify the carrier concerned -you, the consignee, must instigate any
claim. Please retain all packaging in case of future re-shipment.

Page 6G2 Operators Manual
Introduction
The G2 is a powerful DSP based audio dynamics processor, ideally suited for live
sound applications, where it combines the accessibility and immediacy of a pure
analogue design with the quality and accuracy of a digital design in a compact 1U unit.
To achieve this, the G2 has an analogue control surface, following the ‘one control –
one function’ philosophy and a pure digital signal path, with 24-bit conversion, 40-bit
internal processing and a professional 48kHz sampling rate.
The G2 is also available with optional AES/EBU digital inputs and outputs.
Features
♦Look ahead attack for true ‘clickless’ operation and instantaneous opening of
the gate
♦Fully adjustable envelope controls, including hold time (in Gate mode) with
large, easy to see, metering
♦Sidechain EQ built-in including low and high pass filters, and an additional
parametric section with variable stepped gain and high-resolution
frequency adjustment
♦Expander mode –for more subtle gating applications, with gain reduction
metering and fully variable ratio control
♦Stereo link mode locks the sidechains together for perfect stereo tracking as
well as parameter matching
♦Threshold metering to allow accurate and repeatable triggering of the gate
♦AES/EBU Digital input and output interfaces are available as an option.
♦Input and output balancing transformers are also available as an option.

G2Operators Manual Page 7
Front Panel Familiarisation
Level Meter: this meter displays the
instantaneous available headroom available at
the input, just after the analogue to digital
converter.
Active Key: Switches the entire channel
on/off –LED illuminated when processing is
active. Note that the Listen mode may still be
active when the channel is bypassed.
Threshold Control: Set the threshold at which the gate will open, from -40dBu to
+22dBu (effectively off).
Threshold Meter: This meter display the closeness to the threshold, ranging itself
dependant on the setting of the Threshold control and the input level. The yellow
LED shows the point at which the gate will open.
Attack Control: Set how fast the gate will
open (the fade-in time) –the ‘60uS’ setting uses
look ahead delay to open the gate before the
main signal arrives, so preserving the entire
waveform.
Hold Control: Set how long the gate stays fully
open after the signal has dropped below the
threshold, and before entering the release phase.
Release Control: Once the signal has dropped below the threshold and the hold
time has expired, this control determines how quickly it is attenuated (the fade-out
time).
Gate and Gain Reduction Metering: The large green LED is only ever illuminated
when there is less than 6dB of attenuation on the channel (so effectively the gate is
fully ‘open’). As the attenuation increases, this LED goes off, and the red meter
begins to illuminate right to left. This shows increasing gain reduction, until the final
large red LED illuminates when there is more than 40dB of attenuation.
Range/Ratio Control: In Gate mode, this control sets the
maximum attenuation allowed (the Range) when the gate is fully
closed. Note that if the Range is set to less 40dB, the large RED
led may never illuminate. In Expand mode, this control
determines the degree of attenuation as the signal drops below
the threshold.
MODE Key: Switch the channel between Gate mode and
Expand mode. HOLD this key to change modes. Note that the
control markings for Gate mode range are boxed.

Page 8G2 Operators Manual
Sidechain PEQ Gain Key: Adjust the gain of
the sidechain filter to sensitise or desensitise the
gate to certain frequencies. +8/12/20(!) of gain
is available, as well as 0db (off).
Sidechain PEQ Type: Choose the shape of
the sidechain filter between, narrow ‘Q’
parametric and ‘wide ‘Q’ parametric.
Sidechain PEQ Frequency: Select the frequency range over which the sidechain
filter will operate.
High Pass Frequency Control: Cut low frequency content out of the sidechain
signal up to 5kHz.
Low Pass Frequency Control: Cut high frequency content out of the sidechain
signal down to 250Hz.
LISTEN Key: Switches the output of the sidechain filter into the main signal path,
so that the required range of frequencies may be more easily selected. LED flashes as
a reminder that this is selected. HOLD to engage this function.
STEREO Key: Enabling the ‘Stereo’ mode will disable the right hand set
of controls and force both channels to assume the parameter values of the
left channel. The sidechains are also linked so that the two channels track
perfectly, maintaining the stereo image.

G2Operators Manual Page 9
Rear Panel Connections
Power Switch: turns the units mains supply off
and on.
Mains Fuse: located in a finger-proof holder
adjacent to the mains inlet. A spare fuse is also
located in this holder.
Mains Inlet: connected via a standard IEC socket.
Audio In-Out: 3 pin XLR sockets are provided for each
channel. All are fully balanced, pin 2 hot, 3 cold, 1
screen.
Always replace the fuse with the correct type and rating as
shown on the rear panel legend.

Page 10 G2 Operators Manual
Operating the G2
Operation of the G2 is very straightforward, but there are a few points worth noting
which, once understood, will make using the unit even easier.
Switching the unit on and start-up procedure
After plugging in the power and switching the power on using the rear panel switch,
confirmation is quickly given that all is well by various status LEDs illuminating almost
immediately after power-up. These will include, as a minimum, MODE
(Gate/Expand); and Sidechain EQ Type (Wide/Narrow ‘Q’).
The gain reduction will animate and, after the bypass relays disengage, begin to ‘count
down’ accompanied by the output level fading up to normal operating level.
The entire process is complete when the input/output meters and gain reduction
begin to operate normally. This whole start-up procedure only takes a few seconds.
Press-and-hold Keys
The legending on the front panel alerts the user to
the fact that several keys require a ‘press and hold’
action to initiate them. These keys relate to
functions that could accidentally introduce large
changes of level at the outputs, causing undesirable
effects and possible damage. These keys have their
function marked in BOLD (and a different font) to
make it clear that they will only change state if the
key is held in for a time.
The keys in question are…
MODE –switching between gate mode and expand mode (See page 25)
LISTEN –switching the output to monitor the sidechain EQ signal (See page 19)
STEREO –linking the two channels together to operate in stereo (See page 25)
Minimum and maximum control positions To ensure that the G2 is 100%
accurate all of the time, and that what
it says on the front panel is exactly
what the unit is doing, it has been
necessary to introduce ‘end-stops’ on
the controls.
The extreme regions on each control
marked with the curved line designate
this entire region as relating to the parameter value shown. This is to compensate for
the mechanical tolerances of the potentiometers.

G2Operators Manual Page 11
Noise Gate Know-how
Most engineers know the principle reason for using a noise gate –to shut off the
output of some device that, in the absence of the desired output signal, produces (or
passes on) an undesirable level of background noise. The behaviour of the noise gate
is controlled by adjusting, principally, its threshold. This sets the point at which the
level of the desirable signal is deemed quiet enough to turn it off, thereby cutting off
all the background noise as well.
Considering the diagram
shown here, the desired
signal would be the high level
burst and, in between, low
level noise. An example of
this scenario might be the
signal from a bass drum
microphone –a burst of
signal, but perhaps with
unwanted pickup from
lighting dimmers producing a
background buzz.
Setting the threshold just
above the level of the buzz
would keep the gate closed
during periods were the bass
drum was not being played,
only allowing signal through
when the output would be
sufficient to mask the noise
anyway.
The output graph above highlights several other points that are particularly important
with noise gates.
Attack and Release Times.
As the gate opens, there will be a finite delay before the signal crosses the threshold,
cutting off part of the start of the desired signal’s envelope. Similarly, as the signal
drops below the threshold, the gate will close, cutting off some of the end of the
envelope. The diagram above is not truly representative of how the signal
approaching the threshold would be affected.

Page 12 G2 Operators Manual
Controlling the speed at which the gate opens (attack time) and closes (release time)
is crucial to providing transparent operation. Setting the attack time too fast on a
signal that naturally has a relatively slow attack will produce a click. Such a case often
occurs when gating the human voice. The attack time for typical speech or singing is
in the order of several milliseconds –setting the gate to faster than this will make the
voice ‘appear out of nowhere’ with an audible click. This is due to the sudden change
in level from the gate being closed to fully open. The fact that this is a large transient
change will make it sound
like a click. Changing the
‘distance’ between the gate
being closed and open will
remove this click, but also
defeat the purpose of the
gate in the first place –if the
range is set high enough to
prevent the click, it’s
probably not gating the
signal enough anyway.
As mentioned earlier, if the attack is set too slow, the gate will not open in time, and
part of the signal will be lost. For most musical instruments, the essential part of the
signal is the attack phase, as this part identifies the instrument to the human ear.
Hearing only the sustain or
release of a sound makes it
difficult to discern what type
of instrument is being
played, and sounds very
unnatural.
Sudden jump in level as the
gate opens appears as a
click at the start of the
signal.
Start of signal has been lost due
to slow opening of the gate.

G2Operators Manual Page 13
Setting a sympathetic attack time that is similar to that of the required signal will
produce the most natural and transparent results. As the diagram below
demonstrates, the gate opens at a similar rate to the signal, allowing the full attack
portion to be heard. The same rule applies to the
release of the gate –but for
slightly different reasons.
Too slow a release, and
some of the background
noise will be heard as the
gate closes; too fast, and the
signal will be prematurely
cut off, sounding unnatural.
Setting the Range Correctly.
The range control sets how much attenuation is applied to a signal once it drops
below the threshold and closes the gate. It is quite often overlooked when setting up
a gate, the temptation being to set the range at maximum and leave it. When the
gate is fully closed, no signal will be heard when the range is set like this. In some
situations, this much attenuation can sound quite unnatural, especially if the threshold
is set high to gate a loud signal, due to the stark contrast between the gate fully closed
and fully open.
It’s also worth remembering that if the background noise is quite severe, removing it
all will only highlight the noise more when the gate opens and the noise becomes
apparent again. It’s often better to set the range to around 25-30dB of attenuation so
that it can still be heard very slightly.
Using the Hold Time.
When the gate is being used with transient signals that require fast attack but
relatively slow decays, it can be beneficial to introduce a hold time into the gates
envelope. This has the effect of prolonging the time the gate stays open, after the
signal drops below the threshold. The diagram overleaf explains this concept.

Page 14 G2 Operators Manual
Adding some hold time to the envelope can help with tricky situations where the gate
might open and close erratically, such as when there is a lot of background noise.
This problem, coupled with a long release, can cause sporadic bursts of noise to open
the gate in situations when it would be better to hold it open slightly longer.

G2Operators Manual Page 15
Expanders and Expansion –the subtler approach
What does an Expander do?
An expander can be thought of as a complementary device to a compressor. Whilst a
compressor is designed to compress the dynamic range of a signal, an expander is
designed to expand it. The threshold at which the expander begins to operate sets
the point below which the signal begins to be attenuated by a certain amount. The
fact that signals are only ever attenuated defines the behaviour as ‘downward
expansion’ in nature. This distinction is important because if the expander was to
process the dynamic range at a certain threshold, attenuating below the threshold
and amplifying above, even with a low ratio of perhaps 3:1, a limited dynamic range
signal might well end up with a dynamic range well in excess of 120dB, which would
be impossible to utilise, even with the best equipment.
Why are Expanders necessary?
The main use for an expander is to improve the dynamic range of an instrument or
processing device. The dynamic range of any device is limited by two factors –it’s
minimum output, and it’s maximum. It would seem reasonable to assume that the
minimum output would be exactly zero, and that this level should be the same for all
devices. This is definitely not the case. Certainly, when the majority of instruments
and devices are turned off (assuming they are powered in some way) they will all
share a similar minimum output level. However, once on, it is the noise floor of the
electronics within that determines the minimum output. A signal that is below the
noise floor of any piece of equipment will not be resolved by that equipment.
The maximum output level is largely determined by the power supply capabilities of
the device. Many manufacturers (especially Far Eastern) tend to use power supplies
with lower voltage rails, resulting in a poor drive capabilities and limited maximum
output level.
As the expander functions below the threshold, it is in the area of minimum output
level that improvements can be made. Thinking laterally, the noise floor need not just
refer to the electronically generated variety. Noise can be thought of as any
“irregular fluctuations accompanying a transmitted signal but not relevant to it”1.
This may now include other sources of noise such as:
♦Hum due to poor power supply regulation or induced by an earth loop
♦Background interference from lighting dimmers
♦Stage noise picked up from a microphone or transmitted up a microphone
stand
♦Handling noise from a microphone
♦Overspill when ‘miking-up’ a drum kit
1Concise Oxford English Dictionary 2000 Definition 3.

Page 16 G2 Operators Manual
An expander can be used to improve the noise floor under all these circumstances, by
attenuating signals below a set threshold, thereby improving the clarity of the signal
fed to it.
One other area where expander can prove useful is in the control of feedback in a
live situation. In the case of a vocal microphone, leaving it ‘open’ all the time is likely
to cause problems not only with the pick-up of extraneous noise, but allowing
feedback paths to build up. Whilst the vocalist is actually using the microphone, their
voice effectively stops all other sounds from entering. By attenuating the output from
the microphone during pauses, the build up of feedback can be avoided.
How does a Expander work?
Consider again the signal burst shown below. Regions 1 and 3 are set to below the
threshold of the expander, and will consequently be attenuated by an amount
equating to the Ratio parameter. In region 2, the signal has risen to a level above the
threshold, and so the expander will stop attenuating, and allow the signal to pass
straight through. The difference between the attenuated signal when below the
threshold and the original signal level (i.e. the degree of attenuation) is set by the
Ratio. Continuing with the
compressor analogy
again –the ratio can be
determined by
considering the degree
of attenuation required.
If the signal drops to
6dB below the
threshold, and the
ratio is set to 2:1, then
the actual output will
be 12dB down.
The expander is equipped with a set of envelope controls, which allow adjustment of
how it reacts to the signal as it crosses the threshold.

G2Operators Manual Page 17
Examining the purple shaded area in region 3, this represents the release time of the
expander-that is the time for it to achieve full attenuation by the amount set with the
Ratio control, once the signal has dropped below the threshold. The orange shaded
area in region 1represents the attack time of the expander. This is the time period
for the expander to return to the unattenuated level again, the signal having risen
above the threshold. As with a compressor, the setting of the envelope controls is as
important as choosing the correct threshold.
Expanders are
susceptible to the same
abuse as compressors
as far as adjustment of
the envelope controls is
concerned. If the
attack time is too fast,
there will be an audible
‘click’ as the attenuated
signal rises above the
threshold and normal
(unattenuated) gain is
reapplied.

Page 18 G2 Operators Manual
What is the difference between an Expander and a Noise Gate?
In the same way as a limiter can be thought of as a compressor with an infinitely high
ratio, a noise gate is an expander with an infinite ratio. As the expander and noise
gate share similar controls and ultimately work in the same way, consider the burst
diagram below, which demonstrates the action of a noise gate.
As the signal in region
1, is below the
threshold set for the
gate to be ‘open’, the
output will be
attenuated. The
amount of attenuation
applied is not
dependant on a ‘Ratio’
this time, but on the
‘Range’ control setting.
This determines the attenuation in dB’s, which is applied to all signals below the
threshold irrespective of how far below the threshold they are. Whilst the expander
gradually applies attenuation to a greater degree as the signal falls further below the
threshold, the gate will ‘close’ below the threshold applying the number of dB’s of
attenuation set by the ‘Range’ control. If, for example, the threshold is set to 0dB,
and the level drops to –10, if the ‘Range’ is set to 20dB, then the output will be
-30dB: -10 with 20dB of attenuation.
The orange region represents the ‘Attack’ phase of the noise gate, as the signal rises
above the threshold and the gate ‘opens’. The green shaded section is the ‘Hold
Time’ parameter. This has been explained in the earlier section ‘Using the Hold
Time’ in the noise gate section on page 13.

G2Operators Manual Page 19
Sidechain Equalisation –How and When to Use it
When would Sidechain EQ be useful?
When it is necessary to adjust the sensitivity of the gate, tailoring the sidechain signal
with equalisation is the only way to achieve this without affecting the main signal path.
How would sidechain EQ normally be implemented?
Typically, sidechain EQ would be patched into the in/out external path as offered by
the dynamics processor. The G2 obviates the need for this external processing by
including both standard high and low pass filters, and a full frequency band of
parametric EQ in the side chain for each channel.
Picking out instruments for gating.
Sidechain EQ is most often associated with homing in on a band of frequencies to
improve the performance of a noise gate. Being able to exclude extraneous program
material will make the triggering of a gate much more reliable and easier to set up.
The G2’s noise gate (and
expander) offers not only
the high and low pass
filters, but an additional
band of fully parametric
EQ per channel.

Page 20 G2 Operators Manual
This allows the high and low pass filters to be used for the removal of extraneous
program material as normal, but also the parametric to ‘highlight’ any particular band
of frequencies. This can prove very useful in situations where there may
be limited difference between the wanted and unwanted signals.
Being able to accentuate
the wanted band at the
same time as attenuating
the unwanted material,
especially with the added
possibility of highlighting
an one area for triggering
could prove invaluable.