Electro-Voice EQ-231 User manual

Description
The Electro-Voice EQ-231 is a boost-and-
cut stereo1/3-octave graphic equalizer whose
primary use is for tuning the overall fre-
quency response of a sound reinforcement
system, both to increase gain-before-feed-
back and to compensate for the deficiencies
in the acoustic environment and the sound
system.
Features
The variable-Q active filter sets used in the
EQ-231 allow effective equalization with
few problematic side effects. As Figure 1 il-
lustrates, the filter characteristics vary with
the amount of boost or cut used. At low con-
trol settings, the filter Q is very wide. As the
control is boosted or cut, the filter Q nar-
rows so that there is minimum interaction
between adjacent frequency bands.
Each of the 31 1/3-octave filters per channel
provides 12 dB of boost or cut at ISO fre-
quencies 20 through 20,000 Hz (see Figure
2). The faders have a positive detent in the
center, flat-response position.
The gain control also has a center detent at
unity gain. It should be adjusted so that the
adjacentpeakLEDrarelyorneverlights.This
will help achieve maximum possible signal-
to-noise ratio.
The infrasonic low-cut filter, with a 43-Hz
corner frequency and a slope of 18 dB per
octave, is engaged by the front-panel Lo-Cut
switch (see Figure 3). For most applications,
the filter should be engaged. Most profes-
sional speaker systems have little output be-
low45 Hz. At best,driving them in thisrange
wastes amplifier power, and can result in
excessive, ultra-low-frequency cone motion
which distorts the output in the reproduced
frequency range and, most seriously, could
damage the speaker from excessive cone
motion or “bottoming.”
The range select switch allows selection of
either 6 or 12 dB of boost and cut on either
channel. The 6-dB range will allow more
control selectivity while the 12-dB range al-
lows for greater range of adjustment.
The EQ-231 has an IEC connector to allow
compatibilitywith ac connectionsanywhere.
The integral fuseholder also doubles as the
voltage selector to allow for operation any-
where in the world.
Figure 5 shows front and rear panel details.
Architects’ and
Engineers’ Specifications
The equalizer shall have 31 filters for each
channel centered at the ISO standard 1/3-oc-
tave frequencies between 20 and 20,000 Hz.
The filters shall provide either 6 or 12 dB of
boost or cut and be set by 22.5-mm linear
controls. The front panel shall have the fol-
lowing controls: a gain control that is con-
tinuously variable from -12 dB to +12 dB
from unity gain; a high-pass filter with a
slope of 18 dB per octave and a corner fre-
quency of 43 Hz; a range switch to select
either 6 or 12 dB of boost or cut from the
filters; an EQ-on switch to put the filters in
the signal path and an on/off switch.
The rear panel shall have the input and out-
put connectors, a ground-lift switch and a
IEC connector with an integral fuse holder
that allows voltage selection by the way it is
inserted.
The inputs and outputs of the equalizer shall
beaccessiblevia 3-pin XLR-type and 1/4-inch
TRS phone jacks located on the rear of the
unit. The input shall be actively balanced.
The output shall be balanced on the 3-pin
XLR-type plug.
EQ-231
Stereo One-Third Octave
Graphic Equalizer
• 31 1/3-octave filters on each
channel for effective sound
system equalization
• Switchable infrasonic filter and
ground-lift
• Selectable (6 or 12 dB) range of
boost/cut
• Active-balanced 3-pin XLR-type
and TRS 1/4-inch inputs
• Two rack space chassis with
internal power supply with IEC
connector

EQ-231/Graphic Equalizer
EQ-231/Graphic Equalizer
2
The equalizer shall meet or exceed the fol-
lowing performance specifications: fre-
quency response at unity gain, …1 dB 20 -
20,000Hz;totalharmonic distortion less than
0.01%,20 - 20,000 Hz at0 dBu; a noise level
of less than -97 dBu; gain of ±6 dB or ±12
dB; balanced-input impedance of 44,000
ohms; output impedance of 120 ohms; a
maximum input level of +20 dBu at unity
gain; a maximum output level of 20 dBu into
loads greater than or equal to 600 ohms.
The equalizer shall operate on 120 V/240 V
ac,50/60Hz, and consume less than18watts.
The unit shall be operable over the tempera-
ture range as high as 50 degrees Centigrade
or 122 degrees Fahrenheit. The chassis shall
be steel with a gray front panel and black
top, bottom, sides and back with white no-
menclature. The chassis shall occupy one
rackspace in a standard19-inch rack (height:
3.46 inches; depth: 9.24 inches; width: 19
inches). The weight shall be 8.8 lb (4.0 kg).
The equalizer shall have a three-year parts
and labor warranty. The equalizer shall be
the Electro-Voice EQ-231.
Limited Warranty
Electro-Voice products are guaranteed
against malfunction due to defects in mate-
rials or workmanship for a specified period,
as noted in the individual product-line
statement(s)below,orinthe individual prod-
uct data sheet or owner’s manual, beginning
with the date of original purchase. If such
malfunction occurs during the specified pe-
riod, the product will be repaired or replaced
(at our option) without charge. The product
will be returned to the customer prepaid. Ex-
clusions and Limitations: The Limited
Warranty does not apply to: (a) exterior fin-
ish or appearance; (b) certain specific items
described in the individual product-line
statement(s)below,orinthe individual prod-
uct data sheet or owner’s manual; (c) mal-
function resulting from use or operation of
the product other than as specified in the
product data sheet or owner’s manual; (d)
malfunction resulting from misuse or abuse
of the product; or (e) malfunction occurring
at any time after repairs have been made to
the product by anyone other than Electro-
Voice Service or any of its authorized ser-
vice representatives. Obtaining Warranty
Service: To obtain warranty service, a cus-
tomer must deliver the product, prepaid, to
Electro-Voice Service or any of its autho-
rized service representatives together with
proof of purchase of the product in the form
of a bill of sale or receipted invoice. A list of
authorized service representatives is avail-
able from Electro-Voice Service at 600 Cecil
Street, Buchanan, MI 49107 (800/234-6831
or FAX [phone]). Incidental and
Consequential Damages Excluded: Prod-
uct repair or replacement and return to the
customer are the only remedies provided to
the customer. Electro-Voice shall not be li-
ablefor any incidentalor consequential dam-
ages including, without limitation, injury to
persons or property or loss of use. Some
states do not allow the exclusion or limita-
tion of incidental or consequential damages
so the above limitation or exclusion may not
apply to you. Other Rights: This warranty
gives you specific legal rights, and you may
also have other rights which vary from state
to state. Electro-Voice Electronicsareguar-
anteed against malfunction due to defects in
materials or workmanship for a period of
three (3) years from the date of original pur-
chase. Additional details are included in the
Uniform Limited Warranty statement.
For warranty repair or service informa-
tion, contact the service repair department
at: 616/695-6831 or 800/685-2606.
Fortechnical assistance, contact Technical
Support at 800/234-6831 or 616/695-6831,
M-F, 8:00 a.m. to 5:00 p.m. Eastern Stan-
dard Time.
Specifications subject to change without
notice.
FIGURE 1 — Filter Response at
Different Slider Positions Showing Q of
Filter Changing.
FIGURE 2 — Filter Response at ±12-dB
Slider Positions
OUTPUT IN dB
OUTPUT IN dB

EQ-231/Graphic Equalizer
EQ-231/Graphic Equalizer
3
FIGURE 5— Front and Back Panel Details
FIGURE 3 — High-Pass Filter
Response, Upper Trace Lo-Cut Off,
Lower Trace Lo-Cut On
FIGURE 4 — Frequency Response, +6-
dB Gain Position(high-pass filter off)
OUTPUT IN dB
OUTPUT IN dB

EQ-231/Graphic Equalizer
EQ-231/Graphic Equalizer
4
ELECTRONICS–Graphic Equalizer Part Number 532251 — 9937
600 Cecil Street, Buchanan, MI 49107
616/695-6831, 616/695-1304 Fax
©EVI Audio 1999 • Litho in U.S.A.
General Specifications
Conditions:
1. 0 dBu = 0.775 volts rms.
2. 120 volt ac line input voltage
maintained for all tests unless
noted.
3. 0 dBm = 1 mW into 600 ohms.
Frequency Response at Unity Gain,
High-Pass Filter Disengaged
(see Figure 4):
20 Hz - 20,000 Hz …1 dB
TotalHarmonic Distortion at Unity Gain,
20 - 20,000 Hz, 0 dBu Output:
<0.01%
Noise at Unity Gain:
<–97 dBm A-weighted
Front-Panel Controls, Each Channel:
31 center-detent boost/cut slide
controls; level control with center
detent; low-cut select switch; range
select switch; EQ-on switch
LED Indicators, Each Channel:
Peak output level; 6- or 12-dB range
and EQ on
Chassis Construction:
Painted steel
Colors:
Gray front panel with white
nomenclature; black top, sides, rear and
bottom.
Mounting:
Standard 19-in. rack, 3.46 in. high,
9.24 in. deep behind mount
Supplied Accessories:
Power cord; one package of mounting
screws; one package of rubber feet; one
decal and fuse for 230-V ac operation;
owner’smanualandserviceinformation
Operating Environment:
Up to 50° C (122° F)
Power Requirements:
110 or 220 V ac, 50/60 Hz, 18 watts
Overall Dimensions (see Figure 1):
88 mm (3.46 in.) high;
483 mm (19.0 in.) wide;
235 mm (9.24 in.) deep
Net Weight:
4.0 kg (8.8 lb)
Input Specifications
Type:
Electronically balanced
Impedance,
Unbalanced:
22,000 ohms
Balanced:
44,000 ohms
Maximum Input Level at Unity Gain:
+20 dBu (7.75 V rms)
Connectors,
Type:
Parallel female 3-pin XLR-type and
1/4-in. phone jack TRS, balanced or
unbalanced
XLR-type Connector Format (IEC Stan-
dard 268):
Pin 1 shield;
Pin 2 high;
Pin 3 low
Output Specifications
Type:
Electronically balanced XLR-type;
unbalanced 1/4-inch
Impedance,
Balanced:
120 ohms
Unbalanced:
60 ohms
Maximum Output Level:
+20 dBu
Filter Specifications
Type:
Variable-Q active filter set
CenterFrequencies(31bandson ISO one-
third-octave centers for each channel):
20,25, 32, 40, 50, 63, 80, 100,125, 160,
200, 250, 315, 400, 500, 630, 800,
1,000,1,250,1,600, 2,000, 2,500, 3,150,
4,000, 5,000, 6,300, 8,000, 10,000,
12,500, 16,000 and 20,000 Hz
Maximum Boost/Cut
12 dB
Infrasonic Low-Cut Filter,
Corner Frequency (3 dB down):
43 Hz
Slope:
18 dB per octave