TOA P-924A Power Amplifier Instruction Manual

TOA P-924A Power Amplifier

Product Information

Specifications:

• Manufacturer: Toa Electric Co., Ltd.
• Model: 900 SERIES POWER AMPLIFIER P-924A
• Country of Origin: Japan

Frequently Asked Questions

• Q: What should I do if the protection indicator remains lit?
  • A: If the protection indicator remains lit, indicating a muting relay is not activated, disconnect the speaker line, turn off the power, and then turn it back on. If the indicator goes out in about 5 seconds, check the speaker line for short-circuit or overload. If the indicator stays on, there might be an abnormality in the power amplifier stage. In that case, check the power amplifier stage.

Features

1. Wide frequency response; 20 — 20,000 Hz, ±1dB
2. Low distortion and noise level
3. Excellent output regulation
4. A full range of plug-in modules
5. Self-protecting circuitry design
6. Varied output impedances; 4 and 8 ohms, 25 and 70 volts
7. Input level switch (selectable 1,000mV/100mV)
8. Portable or rack-mounting type

General Descriptions

The TOA P-924A Power Amplifier delivers up to 240 watts of power at less than 0.5% total harmonic distortion (THD) from 20 to 20,000 Hz (transformerless 4-ohm output). The P-924A has a high-impedance direct input and an input port (edge connector) to accept one module accessory. Module selection is determined by application among the TOA plug-in modules:

The M-01 series, M-03 series, M-51 series and M-61 series Microphone Preamplifiers, R-01 Mag. Phono Preamplifier, the U-01 series, U-21 series and U-61 series Auxiliary Preamplifiers for high-level sources, the B-01 series Bridging Transformers for bridging high impedance lines, the L-01 series Line Matching Transformers for matching 600-ohm lines, and the S-01, S-02 and S-03 Tone signal generators for generating attention-getting signals and 1 KHz sine wave for testing within the total system. The P-924A has a low-cut switch for a cutoff frequency of 60 Hz, and an input-level switch for input sensitivity of 1V (0dBv) or 100mV (—20dBv). Output terminals provide connections for 4-ohm and 8-ohm speakers, plus 25-volt and 70-volt speaker distribution outlets.

With plug-in modules, the TOA P-924A Power Amplifier may be used as a pre/power amplifier. The P-924A can be rack mounted by using the MB-931A Rack mounting Bracket accessory. The PF-911 Perforated Panel (1.73 inches, 1 rack unit) accessory provides suitable ventilation, finished in color to match the P-924A.

Front Panel Controls and Features

Rear Panel Controls and Features

Connections

Input Connections

• Two types of input terminals are provided on the rear for input connections.

1. 2P terminal (marked HOT, E)
   • It is provided for direct input (unbalanced, 10k ohms) without using plug-in modules. This terminal is directly connected with a potentiometer inside.
2. Plug-in module input
   • Select the desired modules according to the application.

DIRECT INPUT TERMINAL and MODULE INPUT are not usable simultaneously.

• Plug the module into INPUT PORT, sliding it between the guide rails, and secure with two screws.
• When INPUT PORT is not occupied, cover the PORT with the blank panel, and secure it with screws.
• Be sure that INPUT-LEVEL SWITCH is in the proper position for the modules used or the equipment connected to DIRECT INPUT TERMINAL.
• When the P-924A is used in combination with a mixer preamplifier or serves as an incremental power amplifier, normally place INPUT LEVEL SWITCH in “1V (0dBv)” position.

CAUTION

• Modules should not be inserted or removed while the amplifier is turned on.

Plug-in Modules and Input Level SW Setting

*See PLUG-IN MODULES for detail.

Output Connections P-924A

The speaker outputs of the amplifier are 4 ,8 25V and 70V.
Connect speakers to one of these outputs.
Class 2 wiring may be used.
Since these outputs consist of 8 , 25V and 70V via the output transformer (matching transformer) and direct output of 4 the connecting method differs in each case. See the following diagrams.

Note: Impedances indicated below imply total speaker system (load) impedance.

• When connecting speakers to any one of the outputs of 8 , 25V or 70V (BALANCED TRANSFORMER OUTPUT);

< P-924A>

Note

• In this case, the LOW-CUT SWITCH should be “CUT” position.
• This amplifier is characteristically flat even in the low frequency range. Therefore, in TRANS OUTPUT, the acoustic effect and frequency-response characteristics may be altered.
• In TRANS OUTPUT, cut off unnecessary low frequency to obtain the best acoustic condition.

• When connecting speakers to the 4 output. (UNBLANCED DIRECT OUTPUT);

< P-924A>

Installation And Operation

Installation

• Do not block cover ventilation holes.
• The amplifier should not be placed in areas;

1. with poor ventilation
2. exposed to direct sunlight.
3. with high ambient temperature or adjacent to heat-generating equipment.
4. with high humidity or dusty levels.
5. susceptible to vibration.

CAUTION

• Do not remove the case or you may encounter an electric shock.

Operation

When all connections are completed, turn power switch on. Then, the meter is illuminated. Approx. 5 seconds after switching power on, the amplifier comes into operation.

ADJUSTMENT OF VOLUME CONTROL

• Adjust the input volume control to obtain appropriate output level.
• In normal use of BGM playing or announcement, the deflection of the meter is recommended to be within the range as indicated in the drawing. Tone quality will be considerably deteriorated if the pointer indicates around 0 VU.
• The pointer of meter indicates 0 VU if continuous signals like sine waves are applied to the input of the amplifier.
• When the power amplifier is used in combination with a mixer preamplifier, adjust the total gain at the mixer preamplifier with thegain setting of the power amplifier at maximum.

Rack Mounting

• To mount the amplifier in a standard 19-inch equipment rack, use the MB-931A Rack-mounting Bracket accessory.
• Remove 4 screws securing case.

Perforated Panel

PF-911 (OPTION) (Silver)

• If two or more amplifiers are mounted in an equipment rack, space should be provided between the units for ventilation.
• The PF-911 Perforated Panel is recommended for this purpose.

Servicing

Unpacking

• Upon receipt of the amplifier shipment, please inspect for any damage incurred in transit. If damage is found, please notify your local TOA representative and the transportation company immediately.
• State date, nature of damage, whether any damage was noticed on the shipping container, prior to unpacking. Please give waybill number of shipping order.

Failure

• Should amplifier fail, contact your nearest TOA authorized contractor or service center.

Specifications

Specifications are subject to change without notice.

Block Diagram

Block Diagram P-924A

Plug-in Modules

(OPTION)

The TOA PLUG-IN MODULES are suitable for TOA 900 SERIES MIXER POWER AMPLIFIERS A-901A, A-903A, A-906A, and A-912A MIXER PREAMPLIFIER M-900A, POWER AMPLIFIERS P-906A, P-912A, P- 924A, and IN-WALL AMPLIFIERS W-906A, W-912A. Owing to wide selection of types of connectors can also meet the needs of equipment to be connected. MICROPHONE PREAMPLIFIER M-01 series, M-51 series, M-61 series, M-03, M-11 and M-21 incorporates controls for high-cut, low-cut and gain. A gain cotrol is built in MAG. PHONO PREAMPLIFIERS R-01, and AUXILIARY PREAMPLIFIERS U-01 series, U-11 series, U-12, U-21 and U-61, LINE OUTPUT T-01 and AUX INPUTLINE OUTPUT T-02. M-61 and U-61 are built-in compressor circuit to protect the output level from distortion as a result of excessive input and keeps it constant.

M-51 series is built-in voice gate circuit to be automatically activated by presence of signal. U-12 can adjust mute level. T-01 series is an output module with transformer, serving as a line output for recording, etc… A group of special signal generating modules is also available for catching-attention before announcement and testing within the total systems. ALL PLUG-IN MODULES have handles on their front for easy insertion and removal.

FEATURES

1. Wide dynamic range
2. Low noise and distortion
3. Wide frequency response
4. Built-in remote volume control circuit (M-21)
5. Built-in remote master volume or remote volume control circuit. (U-21)
6. Built-in muting circuit to mute incoming signal when MUTE TERMINAL is grounded, (available for modules having 10’s in its model number such as U-11.)
7. Built in muting circuit to deliver or mute its output signal when MUTE TERMINAL is grounded. (M-11)
8. Built-in signal activated muting function (L-41)
9. Presettable gain control (except for B-01, B-11, L-01 and L-11)
10. Microphone modules furnished with tone controls (M-01, M-11, M-21, M-51, M-61, and M-03)
11. Built-in voice gate circuit (to be activated by input signals.) (M-51 series.)
12. All the microphone modules (except M-03) come with phantom powering capability.
13. Built-in compressor circuit (M-61, U-61)
14. Built-in variable muting circuit to adjust the muting level. (U-12)

Plug-in Modules

FRONT PANEL CONTROLS AND FEATURES

Modules with built-in controls are provided in the following six types.

1. GAIN CONTROL

   • This adjusts gam. Turn clockwise (CW) to increase and counter-clockwise (CCW) to reduce gam
   • Set the gam as low as possible, thereby, noise can be reduced, and the maximum permissible input level is raised.
     THRESHOLD (M-61): This adjusts threshold level of compressor. Turn clockwise (CW) to reduce threshold level (to activate the compressor with lower input signal level).
     OUTPUT GAIN (T-02): This adjusts gam of the line output. Turn clockwise (CW) to increase and counterclockwise (CCW) to reduce gam regardless of setting position of the input gam adjust knob.

2. NOMINAL POSITION MARK

   • The left figure shows nominal setting of controls.

3. LOW-CUT FILTER CONTROL 330Hz, 6dB/oct (max. attenuation)

   • This provides flat characteristics at full CW position and attenuation in low frequency by turning CCW. Adjust it to obtain proper tone quality. With low-cut, tone becomes clear.
     MUTE LEVEL (U-12): This adjusts mute level. Turn clockwise (CW) to increase mute level (to be muted excessively) and counterclockwise (CCW) to reduce mute level.
     INPUT GAIN (T-02): This adjusts input gam from AUX. Turn clockwise (CW) to increase gam and counterclockwise (CCW) to reduce.

4. HIGH-CUT FILTER CONTROL 4.2kHz, 6dB/oct (max. attenuation): This provides flat characteristics at full CW position and attenuation in high frequency by turning CCW. Adjust it to obtain proper tone quality. With high-cut, tone becomes soft.
   SENSITIVITY (M-51): This adjusts sensitivity for voice gate.Turn clockwise (CW) to increase sensitivity (to open the gate at full CW position regardless of any input level) and counterclockwise (CCW) to reduce sensitivity.

SPECIFICATIONS IN COMMON

• Load impedance: 10k-ohms
• Mounting: Card-edge connector
• Dimensions in mm (inches) (H) x (W) x (D): 78(3.07)x35(1.38)x88(3.46)

CAUTION

• Modules model M-11. U-11 and U-12 should be used exclusively with model A 901A. 4-903A, A-906A, A-912A. M 900A. W 906A and W-912A

Jumper Wire Setting

M-01, 11, 21, 51, 61

• All the microphone modules come with phantom powering capability. I not desired, cut J1 on the board.

U-21

• Cut J2 on the board to use as a remote master volume control unit Leave J2 on to use as a remote-control AUX module.

U-61

• Cut J2 on the board to use as a compressor unit which goes between PREAMP OUT and POWER AMP IN (LINK IN/OUT).

M-11

Either (both) J3 or (and) J4 is (are) to be cut for a proper operation. Refer to the table below.

• ^Z:
  • Impedance Mute: Normally “On”, becomes “Off” when muting terminals are closed.
  • Mute: Normally “Off”, becomes “On” when muting terminals are closed.

Accessories

Operation And Connections

(Plug-in Modules)

S-01 (1 ,000Hz SINE WAVE)

S-02 (YELP AND BUZZER)

S-03 (ONE-TONE CHIME AND CONTINUOUS ONE-TONE CHIME)

Block Diagrams

Block Diagrams (Plug-in Modules)

Schematic P-924A

Toa Electric Co., Ltd.

KOBE, JAPAN

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