TOA Electronics 1000 Series User Manual

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Operating Instructions

GRAPHIC EQUALIZER

E-1231

TOA 1000 series

 

CAUTION

TO REDUCE THE RISK OF ELECTRICAL SHOCK, DO NOT REMOVE COVER. NO USER SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.

THE LIGHTNING FLASH WITH ARROWHEAD WITHIN A TRIANGLE IS INTENDED TO TELL THE USER THAT PARTS INSIDE THE PRODUCT ARE A RISK OF ELECTRIC SHOCK TO PERSONS.

THE EXCLAMATION POINT WITHIN A TRIANGLE IS INTENDED TO TELL THE USER THAT IMPORTANT OPERATING AND SERVICING INSTRUCTIONS ARE IN THE PAPERS WITH THE APPLIANCE.

Please follow the instructions in this manual to obtain the optimum results from this unit. We also recommend that you keep this manual handy for future reference.

TOA Corporation

Contents

Cautions

2

General Description

3

Features

3

Front Panel

4

Rear Panel

5

Input/Output Connections

6

Installation Precautions

6

Applications

7 • 8

Optional Matching Transformer Mounting

9

Performance Graphs

10

Block Diagram

11

Specifications

12

Accessories

12

Appearance

12

Cautions

1.Do not operate the E-1231 from power mains which exceeds the indicated mains voltage by more than 10%.

2.Do not expose the E-1231 to corrosive chemicals or liquids such as soft drinks, salt water, etc.

3.Always refer the E-1231 to qualified technical service personnel.

— 2 —

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 12dB of boost or cut at each of its 28 frequencies, which are centered at ISO 1/3 octave increments from 31.5Hz to 16kHz.

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 12dB per octave and is variable from 15Hz to 300Hz, while the lowpass filter can set for either a 6dB per octave slope or a 12dB per octave slope and is variable from 2.5kHz to 30kHz.

An input level control on the E-1231 gives ±12dB of adjustment to allow a wide variety of input sources. A LED indicator illuminates when either the input or the output comes within 3dB 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.

Features

1. 28 filters on ISO 1/3 octave center fre-

8.

Variable input level control to accept varie-

quencies from 31.5Hz to 16kHz.

 

ty of input sources.

2. 12dB boost or cut at each center frequen-

9.

Automatic EQ bypass circuitry.

cy, continuously variable.

10.

A security cover is included.

 

3.High quality, low phase-shift active filters.

4.Precision calibrated, noiseless slide controls with center detent.

5.Equalizer In/Out switch.

6.Continuously variable highpass and lowpass filters.

7.LED peak indicator to detect clipping at input or output levels.

11. Filter In/Out switch

12. Lowpass filter can be set for either 6dB/oct or 12dB/oct.

13. Optional input/output transformers that convert electronically balanced input/out- put to transformer balanced input/output.

— 3 —

Front Panel

Lowpass Filter Slope Selection Switch

This switch sets the lowpass filter's per octave attenuation for either 6dB or 12dB.

Peak Indicator LED

The peak indicator LED lights when either the input or the output level reaches 3 dB below clipping.

Input Level Control

This control adjusts the input gain by ±12dB 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.

Lowpass Filter Control

This is a shelving-type filter that provides a 12dB or 6dB per octave roll off above 2.5kHz and up to 30kHz. 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.

Equalizer Sliders

These sliders are adjusted to tune or equalized the overall frequency response of a sound system.

Equalizer Indicator LED

The indicator LED turns on whenever the equalizer IN/OUT switch is "in".

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.

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.

Power Switch

Pushbutton alternately switches the AC power on and off.

Power Indicator LED

The green LED lights when the power switch is "on".

Highpass Filter Control

This shelving-type filter provides an 12dB per octave rolloff between 300Hz and 15Hz. 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.

Filter Indicator LED

The filter indicator LED lights when the filter switch is "in".

Filter IN/OUT Switch

Pressing this switch while equalizer indicator lights provides the frequency response set for by the lowpassand highpass-filter control. Press the switch again to disable the lowpassand highpassfilter control.

— 4 —

Rear Panel

AC Fuse Holder

When replacing, be sure to use the fuse of specified rating and type to avoid the possibility of fire.

Fuse rating

220-240V version 250V T80mA

120V version 250V 0.2A

AC Power Cord

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.

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.

Input Screw Terminal

The input terminal is balanced and 10k ohms in input impedance. Place the supplied short piece between E and C to convert to unbalanced type.

— 5 —

Input/Output Connections

Input terminal from mixer, etc.

E-1231

Input terminal from mixer, etc.

E-1231

Power Amplifier

Speaker System

Installation Precautions

Ground Loops

In any audio system, there are numerous ways by which ground loops can be created. For example, they may occur when the E-1231 is mounted in a rack cabinet, or through AC ground when the E-1231 connected with preamps, mixers, etc. These ground loops may cause hum and noise if care is not taken during connection. An increase in noise from ground loops may be minimized by breaking the ground loop. Generally, the chassis ground of the signal line should be broken as shown below.

When hum is generated from a ground loop, detach a short piece from the ground screw terminal.

— 6 —

Applications

Feedback Prevention

When the overall gain of a sound system is increased, feedback will occur at frequencies where the system response has peaks. Suppose the system has an uneven frequency response like that shown in the following diagram. The frequency at which feedback will occur when gain is increased is about 500Hz. In this case, feedback may be prevented by attenuating

levels at 500Hz by 3dB to 5dB with the E-1231. If the overall gain is again gradually increased, feedback will occur next at about 125Hz. It may be stopped by attenuating the levels 2dB to 3dB at that frequency. In this procedure, sufficient gain in the sound system is obtained before feedback.

Sound Pressure Level

 

 

 

 

 

Room Equalization

 

 

 

Frequency

 

 

 

 

 

In a sound reinfocement system for a room, the clarity

sound clarity.

of sound can be adversely affected by

the room

For example, suppose that there is a room frequency

frequency response including standing waves (room

response as shown below.

resonances), reflections

of

sound,

and

relations

The equalizer sliders are set as shown below.

between direct and indirect sound.

 

 

The overall response after equalization

The E-1231 is an effective

tool to equalize

the room

will then be as follows.

frequency response to a

flat

response

and improve

 

Sound Pressure Level

 

 

 

 

 

 

 

 

 

Frequency

The equalizer sliders are set as shown below.

 

The overall response after equalization will then be as follows.

 

Frequency response

Frequency response

Before equalization

of equalizer

after equalization

Sound Pressure Level

Frequency

— 7 —

Applications

Equalization for music

The Graphic Equalizer is designed not only for use in preventing feedback and equalizing uneven room frequency response to be flat, but also for equalizing frequency response to your tastes and producing favorable sound for you. Fig.1 shows each frequency band and its corresponding auditory feeling. Fig.2 and Table 1 show the relation between each musical instrument and its frequency band. They can be of great help in the equalizer operation. (They are referenced from a book entitled "Practical Guide for concert")

EQUALIZATION CHART

These sounds

The

rhythm

sec-

are felt

more

tion

 

appears

than

really

here.

Either

a fat

heard.

They

or

thin

sound

give a

sense

can

be

heard by

of power.

mis-EQ here. Too

Too

much

much

becomes

produces a

boomy. Bass gui-

muddy sound.

tar-Snare-Toms.

INSTRUMENT CHART

Fig.2

Probably the most im-

Upper vocal region.

Presence

range.

Sibilance

portant of all. Most all

Too much here will

Great achievement

levels

can be

instruments

contain

cause great fatigue,

in overall

level

can

controlled

harmonics

here. 300 Hz

and loose speech in-

be

had

here.

Too

here.

Bright,

boosting can cause horn

telligence. Reducing

little

causes a

"far

clean

defini-

like sounds. 1 k to 2 k

3 k can bring vocals

away" sound.

 

tion.

 

sounds tinny. Too much

on top.

 

 

 

 

 

 

here sounds like the tel-

 

 

 

 

 

 

 

ephone.

Fig.1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

INSTRUMENT EQUALIZATION CHART

 

 

 

Table 1

Acoustic guitar

Bass strings resonate between 70 to 120Hz, body around 300Hz.

Avoid boosting these to stop feedback. 3kHz and 5kHz gives great "clarity".

Electric guitar

Resonances differ-depending on type. Good full sounds around

300 to 500Hz. Clarity at 3kHz.

Bass guitar

Extreme lows are at 60 to 90Hz. "Pick" or "pluck" sounds are around 800 to 1200Hz. Upper harmonics clarified about 3kHz.

Human voice

Good fullness at 150Hz. Watch for "boominess" around 250Hz. Mid-range 10kHz.

Piano (Acoustic)

Bass strings responate around 100Hz. Watch for subharmonics at

30 to 50Hz.

Piano (Electric)

Good mid-clarity at 3kHz to 5kHz thins out rapidly in high end. Be careful around 1.5kHz to 2.5kHz to avoid the "bar room sound".

Organ

Usually dies under 200Hz. Has great mid-sounds around 1200 to

2000Hz. Top end cuts off at 6kHz.

Violin

Richfullness at 400Hz. Natural mids around 1500 to 2500Hz. Avoid "scratch" sounds at 8kHz.

Brass instruments

Watch for "hot" mids around 2kHz. Low end boost around 400Hz. Top end clarity at 6kHz.

Bass drum

Great low "kick" at 40Hz. The mids at 2kHz gives the familiar

"punch".

Snare drum

Good fullness at 100Hz. The "crack" is boosted at 2kHz. Real easy. The snares extend to above 4kHz.

Tom Tom

The main fullness is around 200Hz. The mid punch extends to

4kHz.

Floor Tom

Same as tom, but extends down to 80Hz.

Hi Hat

Watch for the "gong" sound around 300Hz. Good "shimmer" sounds are around 8kHz to 10kHz.

Cymbal overhead

About the same as hi-hat only has more low end around 150Hz.

Talk Box

Depending on the guitar sound driving it and the resonance of each player's mouth, should have great "bite" around 1200Hz and dies above 6kHz.

— 8 —

Optional Matching Transformer Mounting

[CAUTION]

THESE SERVICING INSTRUCTIONS ARE FOR USE BY QUALIFIED PERSONNEL ONLY. TO AVOID ELECTRIC SHOCK DO NOT PERFORM ANY SERVICING OTHER THAN

THAT CONTAINED IN THE OPERATING INSTRUCTIONS UNLESS YOU ARE

QUALIFIED TO DO SO. REFER ALL SERVICING TO QUALIFIED SERVICE PERSONNEL.

The E-1231's input and output are electronically balanced. These can be converted to transformer balanced input and output using the optional matching transformer LT-101 (input) and LT-102 (output).

1.Set the power switch to OFF and unplug the AC cord form a wall outlet.

2.Remove the case by loosening six side panel screws (three each on each side) and two rear panel screws.

3.Install sleeves (supplied with the transformer) by tightening screws from the other side of a chassis, and mount the transformer to the sleeves using screws. See Fig.

1.The

input

transformer

must

be

located

on the left and

the output transformer on

the right.

 

 

 

 

 

 

 

4. When mounting the input transformer, detach

connector from CN-104, reconnect

the detached connector to

connector at the transformer side, and then connect

connector from the transformer to CN104.

 

connector from CN-103,

When

mounting the

output

transformer,

detach

reconnect the detached

connector to

connector at the transformer side, and then

connect

connector from the transformer to CN103.

 

See Fig.1.

 

 

 

 

 

 

 

 

 

Fig.1

5. Fit the case in place.

 

 

Transformer Specifications

 

 

Model

LT-101

LT-102

Frequency response

30Hz ~ 20kHz

30Hz ~ 20kHz

 

(at ±0.15dB)

(at ±0.15dB)

Constant loss

Within 1.5dB(at 1kHz)

Within 1.5dB(at 1kHz)

Distortion

Less than 0.2%(50Hz/5dB)

Less than 0.2%(50Hz/5dB)

0dB = 0.775V RMS

Specifications are subject to change without notice.

— 9 —

Performance Graphs

Frequency Response

(Each slider is set at a max or min position)

Frequency Response (ex. 800Hz slider)

Frequency Response (ex. 630Hz, 800Hz, 1kHz slider)

High pass Filter

Low pass Filter

— 10 —

Block Diagram

— 11 —

Specifications

Frequency Response

±1dB, 20Hz to 20kHz

Total Harmonic Distortion

Less than 0.01% at 1 kHz, all sliders at 0 position, rated output

Equalization Center Frequencies

31.5Hz to 16kHz

31.5Hz, 40Hz, 50Hz, 63Hz, 80Hz, 100Hz, 125Hz, 160Hz, 200Hz, 250Hz, 315Hz, 400Hz, 500Hz, 630Hz,

4kHz, 5kHz, 6.3kHz, 8kHz, 10kHz, 12.5kHz, 16kHz

Rated Input Level

+4dB (INPUT LEVEL CONTROL set for 0 position)

Rated Output Level

+4dB with 600-ohm load

Maximum Input Level

+20dB at 1kHz

Maximum Output Level

+20dB with 600-ohm load

Input Impedance

10k ohms

Output Impedance

600 ohms

Hum and Noise

—94dB (EQ in, all sliders at 0 position, 20~20kHz BPF)

Specifications are subject to change without notice.

Accessories

Security cover

1

Screw for security cover

2

Short piece

2

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

±12dB

Input Level Control

±12dB

Highpass Filter

12dB per octave

Adjustable Cutoff Frequency:15Hz to 300Hz

Lowpass Filter

12dB per octave/6dB per octave

Adjustable Cutoff Frequency:2.5kHz to 30kHz

AC Line Voltage

AC mains, 50Hz/60Hz

Power Consumption

11 watts

Finish

Black

Dimensions

(W X H x D)483 x 88 x 317mm(19.0" x 3.5" x 12.5" )

Weight

4.5kg (9.9lbs.)

Note:0 dB is referenced to 0.775 volts RMS.

Fuse

1

Warranty card (for USA and Canada)

1

Operating instructions

1

Appearance

mm(inch)

TOA Corporation

KOBE, JAPAN

— 12 —

Printed Japan

133-12-037-2A