Buzzaudio REQ-2.2 User manual
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Welcome…
Thank you for choosing the Buzz Audio REQ-2.2 Resonance Equalizer. In this
manual you will find important information regarding the use of the REQ
and we suggest you do read it before using the unit to become familiar
with all the controls and their function.
If after unpacking the REQ you find any damage to the unit you should
contact your dealer or supplier immediately for advice on what to do.
We also suggest you retain the original packaging at least during the
warranty period in case you need to return the unit for service, however we
are confident this will not be necessary!
Contents…
Page
1] Installation Precautions.......................................................3
2] The Mains Input ..................................................................3
3] Audio Connections.............................................................4
4] Overview............................................................................5
5] Controls..............................................................................6
6] Specifications.....................................................................8
7] Warranty/Service Information..............................................9
8] Recall Sheets ...................................................................10
9] Graphs ............................................................................12
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1] Installation Precautions
The REQ-2.2 uses discrete Class A audio amplifiers and these along with the
power supply generate a fair amount of heat. Whilst the casing has many
ventilation holes, care should be taken to avoid racking the REQ along side
other units that run hot. If possible, allow ventilation space between the
REQ and other hot running boxes.
If the REQ becomes too hot, internal parameters may change and this may
show up as clicks when switching the EQ bands in and out.
The REQ also uses wound chokes (inductors) and because these are coils of
wire with many turns, they are prone to picking up mains hum and other
noise in the environs. The REQ chokes are contained within steel housings
to minimize hum induction, however avoid mounting the REQ next to
devices with large unshielded power transformers or switching power
supplies.
2] The Mains Input
As a safety precaution your REQ maybe shipped without a mains fuse fitted.
Before use, you must select the correct mains voltage for your local supply
on the rear panel and fit the correct mains fuse type into the fuse draw for
that voltage.
The factory or your dealer may have already set all this up for you but it
pays to check it before powering up the REQ.
Setting the Voltage Selector…
You will need a medium size flat blade screwdriver.
If your local mains voltage is 100V to 120V set the rear panel voltage
selector to 110V.
If your local mains voltage is 220V to 240V set the rear panel voltage
selector to 220V.
PLEASE NOTE - POWERING UP THE REQ WITH THE WRONG VOLTAGE SETTING
MAY CAUSE SEVERE AND PERMANENT INTERNAL DAMAGE!
Selecting the Correct Fuse…
In the supplied accessories bag you will find;
2x 1 Amp slow blow fuses, FIT for 220V to 240V.
2x 2 Amp slow blow fuses, FIT for 110V to 120V.
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Slide out the fuse draw below the IEC power inlet using a small flat blade
screwdriver and insert the appropriate fuse into the carrier clip. Note there
is also a position in the carrier for a spare fuse (the square tube bit) and we
suggest you store the second supplied appropriate fuse here.
Fitting the wrong fuse may result in the fuse blowing on power up or
inadequate protection. Fitting a fast blow type fuse may also result in the
fuse blowing on power up.
3] Audio Connections
All the XLR connectors on the rear of the REQ-2.2 are balanced and wired
as follows;
Pin 1 = Chassis Ground
Pin 2 = Signal Hot (+)
Pin 3 = Signal Cold (-)
The REQ will accept both balanced and unbalanced inputs, however we
do recommend the use of balanced lines where ever possible. The REQ
has a “looping” input, allowing you to daisy chain it with another device. It
also has two output connectors (paralleled) enabling you to feed two
separate devices if desired.
The REQ output is designed to
drive balanced loads and
each output leg is driven
directly. If you wish to drive
an unbalanced load, you will
need to use a special
connection whereby only Pin
2 and Pin 1 are used and Pin
3 is left floating, ie, no
connection. In this mode the
signal will be 6dB lower than
in balanced mode.
Alternatively an external
audio transformer could be
used to match the REQ into
the unbalanced load.
PLEASE NOTE: A LONG TERM SHORT CIRCUIT ON PIN 2 AND/OR 3 MAY CAUSE
DAMAGE TO THE REQ OUTPUT STAGE.
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4] Overview
The REQ-2.2 is a stereo audio equalizer with four “eq” bands per channel
plus a high pass filter and unique “saturation” module. Front panel controls
allow you to adjust each eq band centre frequency, filter bandwidth (or Q)
and the amount of cut/boost. Each element has it’s own on/off switch
which removes it from the signal path when off.
The high and low bands can be switched from a bell filter to a shelving
filter, and the bandwidth control reverts to a shelf slope control when in
shelf mode. The mid bands can be switched between two frequency
ranges as indicated on the front panel.
There are two versions of the REQ, the standard version and a mastering
version. The differences between the two versions are the high pass filter
turn over frequencies (see graphs at the end of this manual), and the
cut/boost controls. The mastering version utilizes a 23 position stepped
attenuator (+/-8dB range) for the cut/boost control, whilst the standard
version offers a continuously variable +/-16dB range with centre detent.
The REQ uses real chokes and capacitors in a parallel resonant circuit
configuration to generate the eq shapes, and this is why it is called the
Resonance Equaliser. Whilst difficult to implement with adjustable
bandwidth, the sound of these passive resonate circuits is far superior to
that of electronically simulated filters.
Unique to the REQ-2.2 is the saturation module which when engaged, adds
subtle amounts of harmonic distortion to the signal and also alters the low
frequency response (see graphs for detail). The saturation module utilizes a
steel core transformer driven by a “single ended” amplifier to achieve this
effect, and is useful in creating a more “vintage” sound. The effect of the
saturation is dynamic in that the higher the signal level, the greater the
effect will be.
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5] Controls
EQ Band Controls
FREQUENCY – each band has a 12 position frequency control which sets
the centre frequency of the filter. The two mid bands have two ranges of
frequency, and the blue lettering applies when the FREQ x2.5 switch is
illuminated. Please note that if the FREQUENCY switch is parked between
clicks (or detents) the ON and FREQ x2.5 pushbuttons will not function.
BANDWIDTH (low mid and high mid) – a 12 position switch to set the width of
the bell filters ranging from 2 octaves to 0.25 octaves wide. See the graphs
at the end of this manual for more detail.
BANDWIDTH/SLOPE (low and high bands) – the low and high bands can be
switched into shelf mode (BELL/SHELF switch illuminated), and the bandwidth
control reverts to a shelf slope control in this mode. Position 2 is a steep
slope whilst position 13 is a more gentle curve. See the graphs at the end
of this manual for more detail.
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CUT/BOOST – adjusts the amount of eq applied to the signal. The above
drawing shows the standard version with +/-16dB range. The mastering
version of the REQ has a stepped +/-8dB range.
ON – when this switch is illuminated, the associated eq band is engaged
into the signal path. When switched off, the eq band is completely
removed from the signal path.
PEAK – this red LED will illuminate when levels within the REQ circuitry
approach +22dBu warning of possible internal overload. Levels are
monitored at critical points throughout the REQ signal path.
Master Section Controls
HIGH PASS FILTER – a 6 position switch to select roll off frequency of the high
pass filter (HPF). The associated ON switches engages the filter when
illuminated. The drawing above shows the HPF frequency choices for the
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standard version. The mastering version has a different set of frequencies
optimized for stereo program equalisation. See the graphs at the end of
this manual for more detail.
SYSTEM – these switches are used to completely bypass the REQ. When not
illuminated, the REQ input XLR connectors are directly connected to the
output XLR connectors providing a hard wire bypass. Note that the REQ still
does receive signal at it’s input when bypassed.
SATURATION – this 6 position switch selects the type of saturation applied to
signal. The associated ON switches engages the saturation circuit when
illuminated. The saturation control changes the low frequency response of
the REQ as well as introducing low frequency harmonics generated by the
steel audio transformer. See the graphs and specifications for detail.
SWITCH LINKING – from REQ serial number Q1115, a new system control
board has been fitted which allows the HIGH PASS FILTER, SYSTEM and
SATURATION in/out switches to be linked. Once linked, you only need to
push either the A or B channel switches to change both channels together.
To link the functions, press and hold down any of the six switches for 4
seconds. To un-link, press and hold down again any of the six switches.
6] Specifications
Frequency Response
Measured with all eq bands ON set flat, Saturation and HPF OFF........5Hz to 125kHz +0.2/-3dB
See graphs for typical eq and HPF frequency response measurements.
Harmonic Distortion
At +10dBu, Saturation OFF .......100Hz 0.007%...1kHz 0.004%...10kHz 0.007%...100kHz 0.013%
Saturation ON POS-1 ........................................20Hz 1.5%...100Hz 0.07%...1kHz and up 0.01%
Saturation ON POS-2 ........................................20Hz 1.5%...100Hz 0.14%...1kHz and up 0.01%
Saturation ON POS-3 ........................................20Hz 1.5%...100Hz 0.16%...1kHz and up 0.01%
Saturation ON POS-4 ........................................20Hz 1.6%...100Hz 0.17%...1kHz and up 0.01%
Saturation ON POS-5 ........................................20Hz 1.7%...100Hz 0.18%...1kHz and up 0.01%
Saturation ON POS-6 ........................................20Hz 2.0%...100Hz 0.22%...1kHz and up 0.01%
Maximum Input Level.....................................................................................................+25dBu
Input Impedance ...........................................................................................approx 20k ohms
Maximum Output Level............................................+32dBu balanced…+26dBu unbalanced
Output Impedance...........................................................................................approx 70 ohms
Input Common Mode Rejection (ref 0dBu) .................100Hz -65dB…1kHz -65dB…10kHz -60dB
Noise all bands ON set flat........................................-110dB below max input level A weighted
General
Power requirements .......................................................... 115V/230V selectable on rear panel
Dimensions...................................................................................4U rack mount, 300mm deep
0dBu = 0.775V RMS in these specifications. Specifications are typical of a production unit, and subject to change if
we improve something.
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7] Service Information
We are confident that you will receive many years of trouble free operation
from your unit. If however you experience any technical problem with your
REQ, contact your dealer or Buzz Audio for recommendations on what to
do. The modular nature of the REQ construction means most electronic
faults can be easily repaired by swapping out the circuit boards.
For on line support visit our web site; www.buzzaudio.com
Buzz Audio, PO Box 6677, Wellington 6141, New Zealand.
8] Product Warranty
Disclaimer
Buzz Audio is not liable for any damage to microphones, amplifiers,
consoles, speakers or any other equipment and/or electric shock to
humans that is caused by negligence or improper installation and/or use of
the REQ-2.2 Resonance Equalizer.
Standard Product Warranty
Buzz Audio guarantees the REQ-2.2 Resonance Equalizer to be free of
defective materials and/or workmanship for a period of 1 year (12 months)
from the date of sale, and will replace defective parts and repair
malfunctioning products under this warranty when the defect occurs under
normal installation and use – provided the unit is returned to our factory (or
duly authorised service centre) via prepaid transportation with a copy of
the proof of purchase, ie, sales receipt. This warranty provides that
examination of the returned product must indicate, in our judgement, a
manufacturing defect. This warranty does not extend to any product that
has been subjected to misuse, neglect, accident, improper installation, or
where the date code has been removed or defaced. The standard
warranty is NOT transferable.
Product Warranty Extension
The above Warranty may be extended to a period of 2 years (24 months)
from date of sale provided the enclosed Warranty Registration card is
completed and returned to the office of Buzz Audio within 4 weeks (28
days) from purchase date. Alternatively, you may Register your purchase
on-line at our web-site www.buzzaudio.com. The Extended Warranty is
transferable.
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9] Graphs
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