Toa E-1231 User manual

OPERATING INSTRUCTIONS
GRAPHIC EQUALIZER E-1231
Thank you for purchasing TOA's Graphic Equalizer.
Please carefully follow the instructions in this manual to ensure long, trouble-free use of your equipment.
1. IMPORTANT SAFETY PRECAUTIONS ..... 2
2. SAFETY PRECAUTIONS ........................... 2
3. GENERAL DESCRIPTION ......................... 4
4. FEATURES ................................................. 4
5. HANDLING PRECAUTIONS ...................... 4
6. NOMENCLATURE AND FUNCTIONS
Front ............................................................ 5
Rear ............................................................. 6
7. BLOCK DIAGRAM ..................................... 7
8. DIMENSIONAL DIAGRAM ......................... 7
9. SPECIFICATIONS ...................................... 8
Accessories ................................................. 8
TABLE OF CONTENTS

2
When Installing the Unit
• Do not expose the unit to rain or an environment
where it may be splashed by water or other liquids,
as doing so may result in fire or electric shock.
• Use the unit only with the voltage specified on the
unit. Using a voltage higher than that which is
specified may result in fire or electric shock.
WARNING
2. SAFETY PRECAUTIONS
• Before installation or use, be sure to carefully read all the instructions in this section for correct and safe
operation.
• Be sure to follow all the precautionary instructions in this section, which contain important warnings and/or
cautions regarding safety.
• After reading, keep this manual handy for future reference.
Safety Symbol and Message Conventions
Safety symbols and messages described below are used in this manual to prevent bodily injury and property
damage which could result from mishandling. Before operating your product, read this manual first and
understand the safety symbols and messages so you are thoroughly aware of the potential safety hazards.
Indicates a potentially hazardous situation which, if mishandled, could
result in death or serious personal injury.
Indicates a potentially hazardous situation which, if mishandled, could
result in moderate or minor personal injury, and/or property damage.
WARNING
CAUTION
1. IMPORTANT SAFETY INSTRUCTIONS
• Read these instructions.
• Keep these instructions.
• Heed all warnings.
• Follow all instructions.
• Do not use this apparatus near water.
• Clean only with dry cloth.
• Do not block any ventilation openings. Install in accordance with the manufacturer's instructions.
• Do not install near any heat sources such as radiators, heat registers, stoves, or other apparatus (including
amplifiers) that produce heat.
• Do not defeat the safety 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 wide
blade or the third prong are provided for your safety. If the provided plug does not fit into your outlet, consult
an electrician for replacement of the obsolete outlet.
• Protect the power cord from being walked on or pinched particularly at plugs, convenience receptacles, and
the point where they exit from the apparatus.
• Only use attachments/accessories specified by the manufacturer.
• Use only with the cart, stand, tripod, bracket, or table specified by the manufacturer,
or sold with the apparatus. When a cart is used, use caution when moving the
cart/apparatus combination to avoid injury from tip-over.
• Unplug this apparatus during lightning storms or when unused for long periods of time.
• Refer all servicing to qualified service personnel. Servicing is required when the apparatus has been
damaged in any way, such as power-supply cord or plug is damaged, liquid has been spilled or objects have
fallen into the apparatus, the apparatus has been exposed to rain or moisture, does not operate normally, or
has been dropped.

3
CAUTION
• Do not cut, kink, otherwise damage nor modify the
power supply cord. In addition, avoid using the
power cord in close proximity to heaters, and never
place heavy objects -- including the unit itself – on
the power cord, as doing so may result in fire or
electric shock.
• Since the unit is designed for in-door use, do not
install it outdoors. When it gets wet with rain, there
is a danger of electric shock.
• The apparatus shall be connected to a mains
socket outlet with a protective earthing connection.
• The socket-outlet shall be installed near the
equipment and the plug shall be easily accessible.
When the Unit is in Use
• Should the following irregularity be found during
use, immediately turn off this unit's power switch,
disconnect the power supply plug from the AC
outlet and contact your nearest TOA dealer. Make
no further attempt to operate the unit in this
condition as this may cause fire or electric shock.
· If you detect smoke or a strange smell coming
from the unit.
· If water or any metallic object gets into the unit
· If the unit falls, or the unit case breaks
· If the power supply cord is damaged (exposure of
the core, disconnection, etc.)
· If it is malfunctioning (no tone sounds.)
• To prevent a fire or electric shock, never open nor
remove the unit case as there are high voltage
components inside the unit. Refer all servicing to
qualified service personnel.
• Do not place cups, bowls, or other containers of
liquid or metallic objects on top of the unit. If they
accidentally spill into the unit, this may cause a fire
or electric shock.
• Do not insert nor drop metallic objects or flammable
materials in the ventilation slots of the unit's cover,
as this may result in fire or electric shock.
• When replacing the fuse, be sure to use the
supplied one. Using any other fuse than supplied
may cause fire or electric shock.
When Installing the Unit
• Never plug in nor remove the power supply plug
with wet hands, as doing so may cause electric
shock.
• When unplugging the power supply cord, be sure to
grasp the power supply plug; never pull on the cord
itself. Operating the unit with a damaged power
supply cord may cause a fire or electric shock.
• When moving the unit, be sure to remove its power
supply cord from the wall outlet. Moving the unit
with the power cord connected to the outlet may
cause damage to the power cord, resulting in fire or
electric shock. When removing the power cord, be
sure to hold its plug to pull.
• Avoid installing the unit in humid or dusty locations,
in locations exposed to the direct sunlight, near the
heaters, or in locations generating sooty smoke or
steam as doing otherwise may result in fire or
electric shock.
• Be sure to follow the instructions below when rack-
mounting the unit. Failure to do so may cause a fire
or personal injury.
· Install the equipment rack on a stable, hard
floor.Fix it with anchor bolts or take other
arrangements to prevent it from falling down.
· When connecting the unit's power cord to an AC
outlet, use the AC outlet with current capacity
allowable to the unit.
· The supplied rack-mounting screws can be used
for the TOA equipment rack only. Do not use
them for other racks.
· When installing the unit in a rack other than that of
TOA, be sure to use the screws with a diameter of
over 5 mm and length of over 20 mm to mount the
unit. Failure to do so may cause personal injury.
When the Unit is in Use
• If dust accumulates on the power supply plug or in
the wall AC outlet, a fire may result. Clean it
periodically. In addition, insert the plug in the wall
outlet securely.
• Switch off the power, and unplug the power supply
plug from the AC outlet for safety purposes when
cleaning or leaving the unit unused for 10 days or
more. Doing otherwise may cause a fire or electric
shock.
The lighting flash with arrowhead symbol,
within an equilateral triangle, is intended to
alert the user to the presence of
uninsulated "dangerous voltage" within the
product's enclosure that may be of
sufficient magnitude to constitute a risk of
electric shock to persons.
The exclamation point within an equilateral
triangle is intended to alert the user to the
presence of important operation and
maintenance (servicing) instruction in the
literature accompanying the appliance.

4
3. GENERAL DESCRIPTION
The E-1231 is a single channel, 1/3 octave active graphic equalizer designed to allow clean, accurate audio
equalization for stage, studio, or commercial applications.
The E-1231 provides 12 dB of boost or cut at each of its 28 frequencies, which are centered at ISO 1/3 octave
increments from 31.5 Hz to 16 kHz.
The E-1231's active bandpass/bandreject filters are designed for minimum phase shift, and feature smooth
slide controls with center detents for easy and accurate adjustment. (The filters are summed in parallel for
reliability, so that the failure of one filter does not interrupt operation of the others.)
In addition, continuously variable highpass filters are provided on the front panel. The highpass filter has a
slope of 12 dB per octave and is variable from 15 Hz to 300 Hz, while the lowpass filter can set for either a 6
dB per octave slope or a 12 dB per octave slope and is variable from 2.5 kHz to 30 kHz.
An input level control on the E-1231 gives ±12 dB of adjustment to allow a wide variety of input sources. A
LED indicator illuminates when either the input or the output comes within 3 dB of clipping. In addition to the
usual EQ in/out switch, an automatic EQ bypass function provides complete equalization bypass in the event
of loss of AC power, and an output muting function suppresses turn-on/turn-off transients.
A security cover is included with the E-1231 to guard against accidental disturbance, or intentional tampering
when used in fixed installations.
The E-1231 can be mounted in a standard 19" rack and occupies 3-1/2" of vertical space.
4. FEATURES
• 12 dB boost or cut at each center frequency, continuously variable.
• High quality, low phase-shift active filters.
• Precision calibrated, noiseless slide controls with center detent.
• Equalizer In/Out switch.
• Continuously variable highpass and lowpass filters.
• LED peak indicator to detect clipping at input or output levels.
• Variable input level control to accept variety of input sources.
• Automatic EQ bypass circuitry.
• A security cover is included.
• Filter In/Out switch
• Lowpass filter can be set for either 6 dB/oct or 12 dB/oct.
5. HANDLING PRECAUTIONS
• Do not operate the E-1231 from power mains which exceeds the indicated mains voltage by more than 10%.
• When cleaning the unit, be sure to turn the power switch to OFF. Wipe with a soft dry cloth. If it gets very
dirty, use the soft cloth slightly moistened in neutral cleanser. Never use thinner, benzene, chemically
processed towels, or alcohol as the unit’s plastic or other parts may be deformed or discolored.

5
45
11 13
36
12
10
89
2
1
7
6. NOMENCLATURE AND FUNCTIONS
[Front]
1. Power switch
Pushbutton alternately switches the AC power
on and off.
2. Power indicator LED
The green LED lights when the power switch is
"ON".
3. Lowpass filter slope selection switch
This switch sets the lowpass filter's per octave
attenuation for either 6 dB or 12 dB.
4. Peak indicator LED
The peak indicator LED lights when either the
input or the output level reaches 3 dB below
clipping.
5. Input level control
This control adjusts the input gain by ±12 dB to
allow the use of a wide range of input sources.
To insure the best S/N ratio possible, adjust this
control so that the peak LED flashes only
occasionally.
6. Lowpass filter control
This is a shelving-type filter that provides a 12
dB or 6 dB per octave roll off above 2.5 kHz and
up to 30 kHz. Its main purpose is to stop high
frequency noise, oscillation, and certain types of
RF interference from damaging tweeters. It is
also useful in reducing excessive background
noise, such as that produced by old phonograph
records.
7. Equalizer sliders
These sliders are adjusted to tune or equalized
the overall frequency response of a sound
system.
8. Equalizer indicator LED
The indicator LED turns on whenever the
equalizer IN/OUT switch is "IN".
9. Equalizer IN/OUT switch
Equalizer switch puts the input signals either in
circuit or out of circuit of the equalizer. The
"OUT" position provides flat audio response no
matter what the positions of the equalizer sliders
and the filter (LPF/HPF) control.
10. Security cover mounting hole
This hole is used to mount the supplied security
cover with two screws to avoid accidental
changes in set position of control knobs and
switches.
11. Filter IN/OUT switch
Pressing this switch while equalizer indicator
lights provides the frequency response set for by
the lowpass-and highpass-filter control. Press
the switch again to disable the lowpass-and
highpass-filter control.
12. Filter indicator LED
The filter indicator LED lights when the filter
switch is "IN".
13. Highpass filter control
This shelving-type filter provides an 12 dB per
octave rolloff between 300 Hz and 15 Hz. It is
especially useful for reducing stage or turntable
rumble, AC hum, wind noise, and other subsonic
components that waste amplifier power and tax
speakers.

6
15 16 17
14 18
[Rear]
14. AC fuse holder
When replacing, be sure to use the fuse of
specified rating and type to avoid the possibility
of fire.
Fuse rating
E-1231 H: 250 V T80 mA
E-1231 US: 250 V T160 mAL
15. AC power cord
16. Ground screw terminal
Hum can result from a ground loop to be formed
when the E-1231 is connected to other
equipment. In such cases, cut the loop by
removing a short piece, which should usually be
mounted to the terminal.
Note
This ground is not for protective ground.
17. Output screw terminal
The output terminal is balanced and 600 ohms in
output impedance. Place the supplied short
piece between E and C to convert to unbalanced
type.
18. Input screw terminal
The input terminal is balanced and 10 k ohms in
input impedance. Place the supplied short piece
between E and C to convert to unbalanced type.

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7. BLOCK DIAGRAM
POWER
SW
MUTING
RELAY DRIVE
HPF LPF
28-POINT GEQ
INPUT
OUTPUT
H
C
E
FUSE
AC MAINS
PT
PEAK
+15 V –15 V +12 V POWER EQ
EBA
HPF LPF LPF
SLOPE
FILTER
H
C
EEBA
INPUT
POWER SUPPLY
BA
8. DIMENSIONAL DIAGRAM
Unit: mm (in)
[Rear]
[Front]
[Front (without security cover)]
Security cover
466 (18.35)
482.6 (19) 300 (11.81)
317.2 (12.48)
280 (11.02)
4 - 7 × 10.5
[Side]
76.2
88.4
(3)
(3.48)

133-12-037-2C
URL: http://www.toa.jp/
9. SPECIFICATIONS
* 0 dB = 0.775 Vrms
Note: The design and specifications are subject to change without notice for improvement.
• Accessories
Frequency Response 20 Hz to 20 kHz ±1 dB
Total Harmonic Distortion Less than 0.01% (at 1 kHz, all sliders at 0 position,rated output)
Center Frequency 31.5 Hz, 40 Hz, 50 Hz, 63 Hz, 80 Hz, 100 Hz, 125 Hz, 160 Hz, 200 Hz,
315 Hz, 400 Hz, 500 Hz, 630 Hz, 4 kHz, 5 kHz, 6.3 kHz, 8 kHz, 10 kHz,
12.5 kHz, 16 kHz
Rated Input Level +4 dB*(INPUT LEVEL CONTROL set for 0 position)
Rated Output Level +4 dB*, 600 Ωload
Maximum Input Level +20 dB*at 1 kHz
Maximum Output Level +20 dB*with 600 Ωload
Input Impedance 10 kΩ
Output Impedance 600 Ω
Hum and Noise –94 dB*(EQ in, all sliders at 0 position, 20 Hz – 20 kHz BPF)
Indicators A red LED for output and input clipping
A green LED for equalizer IN
A green LED for power ON
A green LED for filter IN
Controls Equalizer Sliders ±12 dB
Input Level Control ±12 dB
Highpass Filter 12 dB per octave
Adjustable Cutoff Frequency: 15 Hz to 300 Hz
Lowpass Filter 12 dB per octave/6 dB per octave
Adjustable Cutoff Frequency: 2.5 kHz to 30 kHz
AC Line Voltage E-1231 H: 220 – 240 V AC, 50 Hz/60 Hz
E-1231 US: 120 V AC, 60 Hz
Power Consumption 11 W
Finish Black
Dimensions 483 (w) x 88 (h) x 317 (d) mm (19" x 3.5" x 12.5")
Weight 4.5 kg (9.92 lb)
Security cover ............................................ 1
Screw for security cover ............................. 2
Short piece ................................................. 2
Fuse ........................................................... 1
Rack mounting screw ................................. 4