TOA Electronics 1000 Series User Manual

Operating Instructions

GRAPHIC EQUALIZER

TOA 1000 series

E-1231

THE LIGHTNING FLASH WITH

ARROWHEAD WITHIN A TRIANGLE IS

INTENDED TO TELL THE USER THAT

PARTS INSIDE THE PRODUCT ARE A

CAUTION

TO REDUCE THE RISK OF ELECTRICAL

SHOCK, DO NOT REMOVE COVER.

NO USER SERVICEABLE PARTS INSIDE.

REFER SERVICING TO QUALIFIED

SERVICE PERSONNEL.

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.

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.

TOA Corporation

Contents

Cautions

General Description

Features

Front Panel

Rear Panel

Input/Output Connections

Installation Precautions

Applications

Optional Matching Transformer Mounting

Performance Graphs

Block Diagram

Specifications

Accessories

7 • 8

Appearance

Cautions

1. Do not opera te 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.

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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-

quencies from 31.5Hz to 16kHz.

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

cy, continuously variable.

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 low-

pass filters.

8. Variable input level control to accept varie-

ty of input sources.

9. Automatic EQ bypass circuitry.

10. A security cover is included.

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.

7. LED peak indicator to detect clipping at

input or output levels.

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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

lowpass- and highpass-filter control. Press the switch again to disable the lowpass- and highpass-

filter control.

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