LA Audio Electronic EQX20 User manual

Dual 3 Band, Mono 6 Band
Parametric Equaliser
OPERATION MANUAL

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Version - V1 April 2000

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CONTENTS
1. Introduction Page 3
2. Installation Page 4
2.1 Inspection and un-packing
2.2 Operating environment
2.3 CE standards
2.4 Power requirements
2.5 Signal levels
2.6 External connections
3. Warranty Page 7
4. Description of controls Page 8
4.1 Channel 1 Page 8
4.2 Channel 2 Page 10
5. Applications Page 11-12
5.1 Setting up and using the EQX20
Audio sweetening and Precision equalisation
Removing subsonics
Making compressors frequency conscious
Special effects
Enhancing the EQ on a mixing console
6. Circuit description Page 13
7. Specifications Page 14
6. Blank panel drawings Page 15

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1.0 INTRODUCTION
The EQX20 is a two channel 3 band Parametric Equaliser which can also
be configured as a single channel 6 band unit. Each band offers variable
Frequency, 15dB cut and boost and variable Q (Bandwidth).
Having all parameters fully variable makes the EQX20 a powerful tool
capable of a range of effects from subtle fine tuning through to radical tonal
changes.
Each channel has a high pass filter switch intended to remove subsonics
such as stage noise and tightening bass sounds.
The facilities provided by the EQX20 are summarised as follows -
• 2 Channel 3 band or single channel 6 band parametric EQ
• Wide frequency sweep (40:1) on each band
• Q variable between 12 (1/12th octave = 1 semitone) to 0.3 (3 octaves)
• ±15dB gain on each band
• High pass filter on each channel
• Bypass switching on each channel
• Balanced inputs on XLR and TRS jack
• Balanced impedance, ground compensated outputs on XLR and TRS
jack
• +4dBu and -10dBV input and output levels
• Low noise and distortion
Typical applications for the EQX20 include -
• Audio sweetening
• Precision equalisation
• Feedback elimination
• Hum, subsonic and noise removal
• Making a compressor frequency conscious
• Special effects
• Enhancing the EQ on a mixing console

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2.0 INSTALLATION
IMPORTANT: PLEASE READ THIS SECTION BEFORE USING THE EQX20
2.1 INSPECTION AND UNPACKING
The EQX20 has been carefully packed at our factory in a carton designed
to withstand handling in transit. Should the unit appear to have been
damaged in transit notify your dealer immediately and do not discard any of
the packing. The carton should contain -
• The EQX20 unit
• Power cord
• Operator Manual (this book)
2.2 OPERATING ENVIRONMENT
The EQX20 is designed to operate between 0 and 50°C (32-122°F) with
relative humidity no more than 80%. Should the unit be installed in an
equipment rack, ensure that the environment conforms to these levels.
2.3 CE STANDARDS AND THE LOW VOLTAGE DIRECTIVE (LVD)
The EQX20 has been designed to meet the latest Electromagnetic
Compatibility (EMC) regulations. However we recommend you do not
operate the unit close to strong emitters of electromagnetic radiation such
as power transformers, motors, mobile telephones or radio transmitters.
The unit should only be connected to a power supply of the type described
in 2.4 POWER REQUIREMENTS or as marked on the unit. The unit must
be earthed for safe operation. Disconnect the mains supply before
removing any cover.
2.4 POWER REQUIREMENTS
There is a mains fuse located inside the unit which is accessed by
removing the cover. This fuse is for protection against unit faults and as
such will not normally need replacing. If you think you have a power related
problem please refer to your dealer.
The voltage and fuse rating have been factory set for -
230V 50mA UK
220V 50mA Republic of Korea
115V 100mA North America
• The correct voltage and fuse rating is indicated on the rear panel.

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• Please check that your unit is correctly rated for the voltage of
the country of operation.
If the fuse requires changing at any time please ensure the correct fuse is
fitted. An incorrect fuse could cause damage to the unit and may constitute
a fire hazard.
If you carry your EQX20 from one country to another it is very important to
ensure the voltage is compatible.
For your information the unit can be internally rewired for use in 230V, or
110-125V countries - contact your dealer for information. A special 100V
version is available for Japan and a 220V, 60Hz version for Republic of
Korea.
The mains lead connections to the appliance are coloured in accordance
with the following code:
Green-and-Yellow Earth
Blue Neutral
Brown Live
• WARNING: THIS APPLIANCE MUST BE EARTHED
2.5 SIGNAL LEVELS
The EQX20 will accommodate both -10dB and +4dB operating levels
without the need for level switching.
PLEASE NOTE: the XLRs are set for +4dBu and the TRS jacks for -10dBV
operating levels. Use the appropriate connector/level to interface between
your equipment and the EQX20.
Using the TRS jack input with +4dB signal levels in some set-ups will over
drive the EQX20 and cause distortion.
Signals in excess of +20dB will cause the unit to distort.
2.6 EXTERNAL CONNECTIONS
Fig 2.6.1 EQX20 rear view showing Input and Output connections

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The input and outputs of the EQX20 are balanced on both XLR and 1/4"
TRS jack connectors. For balanced input and outputs, connections to the
unit should be wired as follows:
TRS jack-10dBV Tip Hot (signal +)
Ring Cold (signal -)
Sleeve Screen (signal ground)
For un-balanced operation join Ring and Sleeve on input, output or both
Sleeve
Screen
Ring
Cold (-)
Tip
Hot (+)
XLR +4dBu Pin 1 Screen (Signal ground)
Pin 2 Hot (+ve)
Pin 3 Cold (-ve)
For un-balanced operation join pins 1 and 3 on input, output or both
Pin 1 = Screen
Pin 2 = Hot (+)
Pin 3 = Cold (-)
PUSH
The 20kΩinput impedance of both inputs is suitable for most types of
equipment.
Plugging a mono jack lead into the TRS input will effectively un-balance the
signal connection.

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3.0 WARRANTY
Your LA Audio EQX20 has been manufactured to a high standard using
quality components. If correctly installed and operated the unit should give
years of problem free operation.
However in the event of a defect in material or workmanship causing failure
of the unit within five years of the date of original purchase we will agree to
repair, or at our discretion replace, any defective item without charge for
labour or parts. To receive service under this warranty it is necessary to
return the unit to an LA Audio authorised service centre or to the factory
with a dated receipt as proof of purchase. After repair the unit will be
returned to you free of charge.
Limitations:
This warranty does not cover damage resulting from accident or misuse.
The warranty is void unless repairs are carried out by an authorised service
centre. The warranty is void if the unit has been modified other than at the
manufacturers instruction. The warranty does not cover components which
have a limited life, and which are expected to be periodically replaced for
optimal performance. We do not warrant that the unit shall operate in any
way other than as described in this manual.

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4.0 DESCRIPTION OF CONTROLS
4.1 CHANNEL 1
LF control
This control sets the amount of cut or boost for the LF (Low Frequency)
section. Gain range on the EQX20 is ±15dB. The following diagram shows
the effect of different cut and boost settings.
Maximum cut or boost occurs at the centre frequency set by the
FREQUENCY control.
Qcontrol
Varies the 'Q' (bandwidth) of the cut or boost region. A low Q, CW (clock
wise) affects a wide band of frequencies whilst a high Q, CCW affects a
very small band. The Q control on the EQX20 has a range of 0.3 (3
octaves) to 12 (1/12th octave). The following diagram shows the effect of
different Q settings.

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In general lower Qs are used when boosting and higher Qs when cutting -
see applications
FREQUENCY control
This control adjusts the centre frequency for LF cut or boost
The LF FREQUENCY control has a 40:1 range and is adjustable from
20Hz, CCW to 1kHz, CW. The following diagram shows the effect of
changing the centre frequency.
MF control
Sets the amount of cut or boost for the MF (Mid Frequency) section.
FREQUENCY control
This control varies the cut or boost centre frequency for the MF (mid
Frequency) section. Control range is 200Hz, CCW to 8kHz, CW.
Qcontrol
Varies the 'Q' of the cut or boost region for the MF section.
HF control

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Sets the amount of cut or boost for the HF (High Frequency) section.
FREQUENCY control
Adjusts the cut or boost centre frequency for the HF section. Control range
is 500Hz, CCW to 20kHz, CW.
Qcontrol
Varies the 'Q' of the cut or boost region for the HF section.
CLIP led
The CLIP led monitors the last stage of the EQ section and indicates signal
levels approaching clipping. The led lights at 3dB before clipping so
momentary peaks are monitored but are not necessarily audible.
Excessive amounts of boost will cause the EQX20 to clip. Remember that
overlapping boost from two sections can also accumulate and cause
overload.

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BYPASS switch
Pressing BYPASS switches the EQ out of the signal path and allows A/B
comparison.
Remember if you are using any amount of boost, BYPASSing the EQ will
cause a noticeable drop in signal level.
In MONO mode Channel 2 BYPASS is inoperative and Channel 1 BYPASS
now switches the whole EQ in and out of circuit.
75Hz switch
Pressing this switch inserts a 75Hz, 12dB/Octave slope high pass filter into
the signal path before the EQ section. Primarily intended to remove
subsonic frequencies such as stage noise the filter can be used in
conjunction with the LF EQ section to tighten a flabby bass sound - see
applications.
In MONO (6 Band) mode only the filter switch on Channel 1 is enabled.
MONO led
Pressing the MODE switch on the rear of the EQX20 lights the MONO led.
This puts the two EQ channels in series to form a single mono 6 band unit.
In this mode the BYPASS and 75Hz filter switches on Channel 2 are
disabled. Channel 1 BYPASS now switches the whole EQ in and out of the
signal path.
Your input signal should now go to Channel 1's input and the output taken
from Channel 2's output. Channel 1 will still output signal but Channel 2's
input is disabled - see applications
5.1 CHANNEL 2
Channel 2 is similar to Channel 1 except for the Input, BYPASS and 75Hz
filter switch when used in MONO mode.
POWER indicator
The green POWER led is lit whenever mains power is supplied to the unit.

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5.0 APPLICATIONS
5.1 Setting up and using the EQX20
Refer to Section 2.6 External connections on page 5 for connecting to and
from the EQX20.
Now unless you are familiar with operating parametric equalisers a good
starting point will be .....
Set all Q controls to 12 o'clock, this gives a Q of around 0.5 (2 octaves)
which is similar to that found on mixers fitted with fixed Q, swept frequency
mid range controls. Use maximum (or nearly) boost so the effect of the EQ
can be clearly heard and now sweep through the frequency range to find
the area that needs attention. This is good practise even if the final solution
involves cutting rather than boosting as boosting produces a more
apparent effect of highlighting the hum, noise, boom or whatever. Gain and
Q should then be adjusted to give the best subjective result.
In general low Qs (wide bandwidth) are useful for boosting without
producing too much peaking or phasing effects. High and Low shelving
type equalisation can be simulated by setting the HF and LF section Qs
fully CW (0.3) and sweeping their associated FREQUENCY controls out
towards the high and low frequency extremes.
High Qs are normally used for cutting sounds such as mains hum or
certain feedback frequencies. In this application Q should be set as high as
possible (narrow bandwidth). Lower Qs and cutting can be used for
reducing boominess found with some acoustic guitars.
A good example of low Q cutting is reducing the 1kHz content of guitars
and snare drums to leave a 'space' for the vocals to sit in. Often cutting in
this way gives a better result than trying to boost the vocals to cut through.
This usually has an added bonus that guitars can stay louder in the mix.
A compressor such as the LA GCX2 may also be used together with
equalisation to bring a hidden vocal forward in the mix.
AUDIO SWEETENING and PRECISION EQUALISATION
The following are a few practical examples which should be treated as
clues, with personal taste, source sounds and material you are creating
deciding the final settings. There are no hard and fast rules, the most
important tools in any equalisation process are your ears.
INSTRUMENT BOOSTING CUTTING

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Kick drum Slap at 3-5kHz Floppy around 600-650Hz
Bass at 40-125Hz Boomy below 80Hz
Snare drum Crack at 2-3kHz 'In the way' 1kHz
Body at 125Hz to 300Hz
Bottom 80Hz

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INSTRUMENT BOOSTING CUTTING
Hi-Hat and Sparkle above 5kHz 'In the way' at 1kHz
Cymbals Ring around 250Hz
Toms Slap at 3.5-5kHz Boomy around 300-350Hz
Bass 60-250Hz
Bass guitar Slap at 1kHz String noise at 1kHz
Bite at 2.5kHz Boomy at 125-220Hz
Bass 40-100Hz
Acoustic guitar Sparkle above 4kHz Boomy at 200-250Hz
Body at 125Hz Tinny at 2-3.5kHz
Electric guitar Sex 600-900Hz Boomy below 80Hz
Bass 125-250Hz 'In the way' 1-3kHz
Bite 2.5kHz
Sparkle at 3-5kHz
Piano Bass below 125Hz Tinny around 1-2kHz
Presence at 5kHz Boomy at 320Hz
It's a sample above 6kHz!
Vocals Presence 3-5kHz Nasal at 1kHz
Cut through 8kHz Sibilance 7-10kHz
Body 150-400Hz Popping below 80Hz
Those who have been paying proper attention will have noticed that on the
same instrument there are suggestions for both cut and boost at the same
frequencies! Well there's no accounting for taste.
REMOVING SUB-SONICS
The 75Hz high pass filter is useful for removing subsonics such as wind
and stage noise and will often help produce a much tighter bass and vocal
sound.
MAKING A COMPRESSOR FREQUENCY CONSCIOUS
Inserting the EQX20 into the side chain of a compressor such as the GCX2
will make the compressor more sensitive to certain frequencies. Examples
of this technique are De-Essing and De-Popping.
SPECIAL EFFECTS
A passable telephone voice can be created by cutting frequencies below
300Hz and above 3kHz. Use the LF and HF sections, lowest Q (CW)
setting and adjust their respective FREQUENCY controls accordingly.

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Adding a high Q peak around 1kHz with the MF section will further
enhance this effect.
ENHANCING THE EQ ON A MIXING CONSOLE
Patch the EQX20 into the insert points on your console to add further
equalisation capabilities when treating individual sounds. Or patch into
Group inserts for equalising sub-mixes or into the Stereo inserts for overall
mix EQ.

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6.0 CIRCUIT DESCRIPTION
Audio
input
High pass
filter
Audio
output
Clip
Equaliser
Bypass
Bypass
Fig: 6.0.1 Block diagram of the LA EQX20 showing the main signal paths
AUDIO PATH
The input signal first passes through the electronically balanced input stage
which provides RF filtering and rejection of common mode noise signals.
The signal then passes through the High pass filter and equalisation stages
and is output via the ground compensated output amplifier.
FILTER
The filter section is a standard 2 pole, -12dB/octave high pass design
optimised for minimum ripple in the pass band. The -3dB frequency for this
filter is 75Hz.
EQUALISER
The equaliser section is based on a State Variable Filter which provides
variable Gain, Frequency and Q with very little interaction between the
controls. There are 3 stages in series for each channel.
OUTPUT
The output stage is a balanced impedance, ground sensing amplifier which
provides level matching and a low impedance output. The outputs are also
RFI protected.
MONO mode
In MONO mode the output of Channel 1, pre output stage is fed directly
into the EQ section of Channel 2.
Signal is still output from Channel 1 but has not been affected by the EQ
settings of Channel 2.
BYPASS and 75Hz filter switching is controlled by Channel 1, Channel 2's
switches are disabled. Only one filter is used in this mode.

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7.0 SPECIFICATIONS
INPUTS
Type electronically balanced
XLR-F +4dBu, wired pin 2 = hot (signal +)
1/4' TRS jack -10dBV, wired Tip = hot
Impedance 20kΩ
Maximum input +20dBu
OUTPUTS
Type Ground sensing, balanced impedance
XLR-M +4dBu, wired pin 2 = hot (signal +)
1/4" TRS jack -10dBV, wired Tip = hot
Impedance 100Ω(+4dBu output)
Max. output +20dBu
PERFORMANCE
THD < 0.01%, +4dBu output
Noise < -86dBu (20Hz to 20kHz)
Frequency response ±1dB, 20Hz to 20kHz, EQ 'in'
CONTROLS
GAIN ±15dB
FREQUENCY LF = 20Hz to 1kHz
MF = 200Hz to 8kHz
HF = 500Hz to 20kHz
Q 0.3 (3 octaves) to 12 (1/12 octaves)
CLIP led lights 3 dB before clipping
HIGH PASS FILTER -3dB at 75Hz, -12dB/Octave
POWER SUPPLY
Mains voltages 230VAC, 50Hz, 6VA Europe
115VAC, 60Hz, 6VA North America
220VAC, 60Hz, 6VA ROK
Mains connectorStandard IEC receptacle
MECHANICAL

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Dimensions 1.75" (44mm)H x 19" (482mm)W x 6.5" (165mm)D
Weight Unit = 2.2kg, Shipping = 2.85kg
LA Audio reserves the right to alter any feature or specification without prior notice E&OE

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